Synthesis and kinetic investigations of macromolecular polymeric catalysts

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Synthesis and kinetic investigations of macromolecular polymeric catalysts
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Polymers   ( lcsh )
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Thesis:
Thesis (Ph. D.)--University of Florida, 1984.
Bibliography:
Includes bibliographical references (leaves 70-71).
Statement of Responsibility:
by John Carter Leighton.
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Typescript.
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Vita.

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Full Text









SYNTHESIS AND KINETIC INVESTIGATIONS
OF MACROMOLECULAR POLYMERIC CATALYSTS






BY

JOHN CARTER LEIGHTON


A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL OF
THE UNIVERSITY OF FLORIDA
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE
DEGREE OF DOCTOR OF PHILOSOPHY

UNIVERSITY OF FLORIDA
1984



























TO JEANNETTE














ACKNOWLEDGEMENT

I wish to thank Professor James A. Deyrup for suggesting this

problem and for his help and support (scientific, moral, and financial)

along the way. It has been a pleasure to work in his lab.

My Mom and Dad have done much more for me than I'll ever deserve

and I am eternally grateful to them.

I leave Gainesville with many fond memories of good times and

good friends. Special among them are Professor Bill Dolbier, Simon

Sellers, Tes Toop, Dan Daly, Jim Keay, Dave Winwood, Victor King, and

Ann Mobley. I shall miss them all very much.

Lastly, and mostly, I thank my beautiful wife Jeannette for

persevering with me over the last two years. Her encouragement and

understanding has often made the difference.













TABLE OF CONTENTS

page
ACKNOWLEDGEMENT. . . ... iii

LIST OF TABLES . . ... ....... vii

LIST OF FIGURES. . . ... ..... ix

ABSTRACT. . . .. . xi


CHAPTER 1









CHAPTER 2















CHAPTER 3


A NEW APPROACH TO THE SYNTHESIS OF
POLYMERIC CATALYSTS . .

Introduction. . . .

Discussion . . .

Proposal of Research. . .


SYNTHESIS OF MONOMERS AND POLYMERS. .

Synthesis of Monomers. . .

Synthesis and Model Reactions of
Hydroxylamine Cleavage Reagents. .

Synthesis of Polymers. . .

Hydroxylamine Cleavage Reaction on
Polymers. . . .

Dealkylation of Polymer-Bound
Hydroxamate Ester. . .


KINETIC EVALUATION OF POLYMER CATALYSTS. .

Introduction . . .

Preliminary Experiments. . .







Kinetic Comparison of Ordered and
Random Bifunctional Polymers . ... 45

Burst Kinetics . . 47

Conclusion. . . ... 50


CHAPTER 4 EXPERIMENTAL PROCEDURE. . .. 51

Introduction . . ... 51

Synthesis . . ... 51

N-(p-Vinylbenzoyl)-4(5)-vinylimidazole 14. 51
N-(p-Vinylbenzoyl)-5(6)-vinylbenzimidazole 15 52
4(5)-Vinylimidazole 16. . 52
N-(p-Vinylbenzoyl)imTiazole 17 .. ..... 53
5(6)-Vinylbenzimidazole 18. .. 53
N-(p-Vinylbenzoyl)benzimTdazole 19. .. .... 54
N-Methyl-o-benzyl Hydroxylamine Hydrochloride
20 . ... 54
p-Vinylbenzoic Acid 22 ............ 55
p-Vinylbenzoyl Chloride 23 .. 55
B-(4-Formamidophenyl)ethi-y Formate 26. .. .. 56
B-(3-Nitro-4-formamidophenyl)ethyl Formate 27. 56
B-(3-Amino-4-formamidophenyl)ethyl Formate 28. 56
5(6)-(B-Hydroxyethyl)benzimidazole 29. 57
5(6)-(B-Chloroethyl)benzimidazole
Hydrochloride 30 . ... 57
Benzyl N-Methylbenzohydroxamate 33. .. .... 57
Ethyl (N-Hydroxy)ethanimidate 38. 58
p-Methoxybenzyl Chloride 39.. .. .... 59
Ethyl N-(p-Methoxybenzyloxy)ethanimidate 40. 59
o-(p-Methoxybenzyl)hydroxylamine
Hydrochloride 41 . ... 60
p-Methoxybenzyl Benzohydroxamate 42. .. .. 60
(p-Methoxybenzyl) N-Methylbenzohydroxamate 43 61
N-Methyl-o-(p-Methoxybenzyl)hydroxylamine
Hydrochloride 44 . ... 61
PS-DVB-VBVIm 46. .. .... .. 62
PS-DVB-Vim-VBIm 47 . .. 62
Mono-PS-DVB-VIm 48 . ... 63
PS-DVB-VBVBenz 49. . .. 63
PS-DVB-VBenz-VBBenz 50. . 63
Mono-PS-DVB-VBenz 51. . .. 64
PS-DVB-VBBenz 52. . ... .. 64
Polymers 54-58. General Method of
Cleavage by Anion 53 . ... 65
Polymers 59-63. General Method of
Dealkylation of Polymer-Bound
Hydroxamate Ester . ... 66








Kinetics. . .. 66

General Kinetic Method. .. 66
Sample Site Access Calculation. ... 67

Sample Calculation of Polymer Elemental
Composition. . ... 68
REFERENCES. . ... . . 70

APPENDIX. . . .... 72

BIOGRAPHICAL SKETCH. ... . ... 85









LIST OF TABLES


page
Composition of imidazole-containing
polymers. . . 30

Composition of benzimidazole-containing
polymers. . . .. 30


Table

II-1


II-2


III-1




III-2




III-3




III-4




III-5





III-6




III-7




III-8


. 39




. 40




. 40




. 41


The effect of blank polymer on the pseudo
first order rate constants for imidazole-,
benzimidazole-,
and N-methyl-(p-tolyl)hydroxamic acid-catalyzed
hydrolysis of DNPB . .. 43

Pseudo first order rate constants for the
hydrolysis of DNPB in the presence of
ordered and random bifunctional polymeric
catalysts. . . 45

Pseudo first order rate constants for the
hydrolysis of DNPB in the presence of
ordered and random bifunctional polymeric
catalysts. .. . . 45

Pseudo first order rate constants for the
hydrolysis of PNPA in the presence of
ordered and random bifunctional polymeric
catalysts. . . ... 46


Pseudo first order rate constants for the
hydrolysis of DNPB in the presence of
mono-functional polymeric catalysts and
soluble analogs . .

Pseudo first order rate constants for the
hydrolysis of DNPB in the presence of
mono-functional polymeric catalysts and
soluble analogs . .

Pseudo first order rate constants for the
hydrolysis of PNPA in the presence of
mono-functional polymeric catalysts and
soluble analogs . .

Pseudo first order rate constants for the
hydrolysis of PNPA in the presence of
mono-functional polymeric catalysts and
soluble analogs . .









111-9 Pseudo first order rate constants for the
hydrolysis of PNPA in the presence of
ordered and random bifunctional polymeric
catalysts. . . 46

III-10 Accessibility of functional groups on
macroporous copoly(styrene-divinylbenzene)
determined by burst kinetics. . ... 49


viii


Table


page







LIST OF FIGURES


Figure page

I-1 Functional groups at the active site
of a-lytic protease. . .. 2

I-2 Solvolysis of p-nitrophenyl acetate by
poly-4(5)-vinylimidazole and imidazole. 4

I-3 Proposed catalytic interactions between
neutral and anionic imidazole on a polymer
backbone . . 5

I-4 Proposed mechanisms of bifunctional action
in copoly-(4)5-vinylimidazole-p-vinylphenol 6

I-5 Plot of concentration of dinitrophenol versus
time for MHA-VIm, MHA-AAm, and VIm-AAm
under burst conditions. . 7

I-6 General base assistance of deacylation
by imidazole. . . 7

I-7 Plot of ka,obs versus HA. . 8

I-8 A. Direct acylation of hydroxamate anion.
B. Imidazole assisted acylation of neutral
hydroxamic acid. . ... 9

II-1 Synthetic sequence leading to imidazole/
hydroxamic "active sites" on a macroporous
polymer . . 19

11-2 Synthetic sequence leading to random
distribution of imidazole and hydroxamic
acid on a macroporous polymer. ... 20

11-3 Synthetic sequences leading to macroporous
polymers containing only imidazole or
benzimidazole groups. . .21

II-4 Synthetic sequence leading to polymer
containing only hydroxamic acid groups. ... 22

II-5 Imidazole-containing macroporous polymers
synthesized . .. 31

II-6 Benzimidazole-containing macroporous polymers
synthesized . . 32








Figure page

II-7 Hydroxylamine cleavages carried out on
imidazole-containing macroporous polymers. .... .34

II-8 Hydroxylamine cleavages carried out on
benzimidazole-containing macroporous
polymers . . 35

II-9 Removal of the O-(p-methoxybenzyl)
substituent on polymers 54-58. . ... 37

III-I Burst kinetics of a-chymotrypsin catalyzed
hydrolysis of PNPA. . ... 47














Abstract of Dissertation Presented to the Graduate
Council of the University of Florida in Partial
Fulfillment of the Requirements for the
Degree of Doctor of Philosophy


SYNTHESIS AND KINETIC INVESTIGATIONS OF
MACROPOROUS POLYMERIC CATALYSTS

BY

JOHN CARTER LEIGHTON

April 1984



Chairman: James A. Deyrup
Major Department: Chemistry

Functionalized highly crosslinked macroporous polymers were

investigated as nucleophilic catalysts for esterolysis. Polymeric

catalysts containing imidazole or benzimidazole were synthesized by

the copolymerization of styrene and divinylbenzene with 5-(6)-vinyl-

benzimidazole or 4(5)-vinylimidazole. Catalysts containing hydroxamic

acid functionality were obtained by a step-wise procedure involving the

copolymerization of styrene and divinylbenzene with N-(p-vinylbenzoyl)-

benzimidazole followed by hydroxylamine cleavage of the polymer-bound

benzimidazolide. These monofunctional catalysts were compared with

soluble model catalysts. The heterocycle containing polymers showed

increased catalytic efficiency relative to their soluble models;

however, the hydroxamic acid containing polymer was considerably less

catalytically active than its soluble model.






"Ordered" bifunctional catalysts containing the hydroxamic acid

functionality in close proximity to either an imidazole or a benzimidazole

were also prepared. These were kinetically compared to catalysts

containing the two functional groups distributed randomly with respect

to each other. However, no significant difference in catalytic

efficiency was found between the catalysts containing the functional

groups in "ordered" and "random" distributions. The polymer catalysts

were found to follow burst kinetics. This was interpreted as evidence

for nucleophilic catalysis and used to calculate the percentage of

kinetically accessible polymer-bound functional groups.













CHAPTER 1

A NEW APPROACH TO THE SYNTHESIS
OF POLYMERIC CATALYSTS

Introduction

Functionalized polymers can act as efficient catalysts for organic

reactions. The design of such polymeric catalysts has generally followed
1-4
the prototype of enzymes. Two properties of enzymes are critically

important to catalytic activity: 1) binding of the substrate at the ac-

tive site, and 2) cooperation of functional groups at that active site.

These properties must be incorporated into the design of polymeric

catalysts.

The contribution of substrate binding to catalytic activity has been

demonstrated by the observation of so-called Michaelis-Menten kinetics

(equation 1).


k, k2
E + S ES ---> E + P (1)
k_,

In the kinetic scheme shown in equation 1, free enzyme (E) and sub-

strate (S) are in equilibrium with an enzyme-substrate complex (ES). As

product (P) is formed from this complex, the enzyme is regenerated. The

rate of product formation depends directly upon the concentration of ES,

hence the importance of substrate binding.

The cooperation of functional groups present at the enzymic active
6
site is considered to be necessary for efficient catalysis. The active

1








site of a-lytic protease, an enzyme which catalyzes the hydrolysis of

amide bonds, contains a carboxylic acid, an imidazole, and a primary

alcohol. Studies utilizing 15N nmr indicate that the imidazole is hydro-

gen bonded to the acid and the alcohol as shown in Figure I-1. The




__-- --
CH2 CH CH2

0 N-H-N N --- H





Figure I-1. Functional groups at the active site of a-lytic protease.

authors suggest that this favors the imidazole tautomer with hydrogen

on N-3 rather than on N-1, which allows the imidazole to act as a general

base toward the alcohol in catalysis.

The importance of cooperation between functional groups for efficient

enzymatic catalysis is intuitively understandable when one considers that

enzymes such as a-lytic protease are, after all, nucleophilic catalysts.

A kinetic scheme for nucleophilic catalysis of amide hydrolysis is shown

in equations (3) and (4).



NuH + RCONHR' > NuCOR + R'NH2 (3)

NuCOR + H20 > NuH + RCO2H (4)







In equation (3), the protonated nucleophile (NuH) attacks the amide

substrate to form an acyl-nucleophile intermediate (NuCOR) with the re-

lease of the amine component of the amide. The acyl-nucleophile inter-

mediate then reacts with water to regenerate the protonated nucleophile

and release the carboxylic acid component of the amide, as shown in equa-

tion (4). By this scheme, water is the final acyl group acceptor. Three

requirements must be met for efficient catalysis to occur by such a

scheme:8

1) The catalyst must be more nucleophilic than the final acyl group

acceptor (water).

2) The acyl-nucleophile intermediate formed in the first step must

be more reactive than the substrate.

3) The acyl-nucleophile intermediate must be thermodynamically

less stable than the products.

The existence of all of these properties in a catalyst is unusual.

In general, a functional group that is a good nucleophile is also a poor

leaving group. Conditions meeting requirement one tend to be antagonis-

tic to those needed for requirement two and vice versa. One can, however,

envision an efficient catalyst being made up of two functional groups:

a strongly nucleophilic group and a second functional group to aid in

the deacylation of the intermediate.

Research in this area was pioneered by Overberger, who first compared

the catalytic effects of poly[4(5)-vinylimidazole] and monomeric imida-

zole on the hydrolysis of p-nitrophenyl acetate.9 Figure I-2 shows a plot

of the second order rate constant (kcat) versus the fraction of neutral

imidazole (a,) for both polymeric and monomeric imidazole.















kcat





0.2 0.4 0.6 0.8 1.0

a,


Figure 1-2. Solvolysis of p-nitrophenyl acetate by poly-4(5)-vinyl-
imidazole (,) and imidazole (o).


The nearly linear dependence of the second order rate constant

kcat for monomeric imidazole on a, is in sharp contrast to the sharp in-

crease in kcat for polymeric imidazole at high a, values. At high pH,

where approximately 90% of the imidazole is in the neutral form, poly-

meric imidazole exhibits a stronger catalytic effect than monomeric imi-

dazole. The authors attributed this catalytic enhancement to cooperative

interactions between neutral and anionic imidazole on the polymer back-

bone (see Figure 1-3).

More recent studies by Lege and Deyrup have shown that such pH-

dependent catalytic enhancements are the result of electrostatic effects
10-11
on the nucleophilicity of polymer bound substituents. In these

studies, imidazole, pyridine, and 2-aminopyridine were attached to par-

tially dodecylated poly(ethylenimine) to yield their respective macromole-

cular catalysts. The second order rate constants for the hydrolysis of

p-nitrophenyl acetate of all these catalysts exhibit a dependency on pH










HN

N

H


Figure 1-3. Proposed catalytic interactions between neutral and anionic
imidazole on a polymer backbone.
9

that is very similar to that observed by Overberger in the poly-4(5)-

vinylimidazole system. However, the observed similarities in the be-

havior of the polymer bound 2-aminopyridine (which might profit from

deprotonation in the transition state) and polymer bound pyridine (which

could not profit from such assistance) makes bifunctional catalysis in

these systems unlikely. Deyrup concluded that the amount of charge on

a polymer has a major impact on the nucleophilicity of any substituents

on that polymer whether or not the substituent itself is protonated.10

Polymers containing two different functional groups have been syn-

thesized in the search for cooperative catalytic effects. Overberger et al.

fused 4(5)-vinylimidazole and p-vinylphenol in a linear copolymer and

studied its catalytic effect on the hydrolysis of 3-acetoxy-N-trimethyl-

anilinium iodide.2 At pH 9.1 this copolymer gave a rate enhancement

approximately 63 times that of imidazole. It was also noted that neither

phenol, poly-p-vinylphenol, poly-4(5)-vinylimidazole, nor copoly-(4) 5

vinylimidazole-p-methoxystyrene had any effect on the solvolytic rate in







the pH region investigated. The authors proposed bifunctional catalysis

involving imidazole and phenolate ions along with electrostatic attrac-

tion of the substrate to the polymer chain to account for the catalytic

effect (see Figure 1-4). 0

N R-C-OR

N I
HH
R-C-OR NtJ
I 0
H II
O H R C---OR
00-
o- O -






Figure 1-4. Proposed mechanisms of bifunctional action in copoly-(4)-
5-vinylimidazole-p-vinylphenol.

Kunitake and Okahata have studied the hydrolysis of p-nitrophenyl

acetate by a linear copolymer of N-methylacrylohydroxamic acid and 4(5)-

vinylimidazole (MHA-VIm).13 As controls, linear copolymers of N-methyl-

acrylohydroxamic acid with acrylamide (MHA-AAm) and 4(5)-vinylimidazole

with acrylamide (VIm-AAm) were synthesized.

Kinetic comparison of these catalysts under burst conditions (excess

substrate) gave the results shown in Figure I-5. Analysis of the pre-

steady state portion of the MHA-AAm curve and the VIm-AAm line shows

that the polymeric hydroxamic acid is acylated 10-102 times faster than
the polymeric imidazole. However, the steady state portion of the MHA-
AAm curve is horizontal, indicating that deacylation of the intermediate









MHA VIm






MHA AAm


VIm AAm


0 100 200

t


300 400

(sec)


Figure 1-5. Plot of concentration of dinitrophenol versus time for MHA-
VIm, MHA-AAm, and VIm-AAm under burst conditions.


is immeasurably slow. The positive slope of the steady state portion of

the MHA-VIm curve indicates that the imidazole accelerates the deacylation

of the acyl-hydroxamate intermediate. The observation of a solvent kine-

tic isotope effect for the rate of deacylation (kH/kd = 3.2 at pH 9.0)

led Kunitake to propose the action of imidazole as a general base in the

deacylation process (see Figure 1-6).





0H
HN-H

N -- H N. -H -- N
3H O C N o
C-CH3 CH3 0-


Figure 1-6. General base assistance of deacylation by imidazole.


SCC
CO
S0
-E r..








Even more important was the finding of a concerted action involving

both the VIm and MHA groups in the acylation process. Figure I-6 gives

plots of the apparent rate constant for acylation of hydroxamic acid, ka,,

obs, versus the fractional dissociation of hydroxyamic acid (aHA). The

graphs show that the neutral form of MHA-AAm is catalytically inactive;

MHA-VIm





ko,obs


MHA-AAm


0 0.1 0.2 0.3 0.4 0.5
a HA
Figure 1-7. Plot of ka, obs versus aHA'


that is, kg, obs equals zero when aHA equal zero. The neutral form of

the bifunctional polymer is catalytically active, as evidenced by the

positive y-intercept. A solvent kinetic isotope effect (kH/kd = 1.6

at pH 7-8) was found for the intercept but not for the slope. This ob-

servation was interpreted as evidence for a proton transfer in the tran-

sition state leading to acylation of undissociated hydroxamic acid.

Kunitake and Okahata therefore proposed two major courses of acylation:

direct acylation of hydroxamate anion and imidazole assisted acylation
13
of undissociated hydroxamic acid (see Figure 1-8).

Although impressive cooperative effects have been demonstrated in

these bifunctional linear copolymers, there seem to be limitations in the

overall approach. Cooperative catalysis in these systems is random in

nature, relying on conformational changes in the polymer to bring functional










OR II
S N N
/ 0- C CH 0-H N N-H
CH,3
R R-C-OR
II
0

A B


Figure I-8. A. Direct acylation of hydroxamate anion. B. Imidazole
assisted acylation of neutral hydroxamic acid.

groups together as an "active site." Such a reliance on conformational
flexibility is not in keeping with the prototype of the hydrolytic enzymes.
In contrast, a catalyst based upon a rigid polymer matrix would not
rely on random flexing of the polymer chain to bring functional groups
together. A rigid matrix would allow the construction of "active sites"
in the polymer. These "active sites" would consist of two or more func-
tional groups held in close proximity of each other by the rigid polymer
matrix.
The ability of highly cross-linked macroporous polymers to hold
functional groups in close proximity has been demonstrated. Wulff' copoly-
merized bis(p-vinylbenzyl)disulfide 1 into a macroporous copoly(styrene-
divinylbenzene) matrix and reductively cleaved the disulfide linkage to


D CH2-S-S-CH2 CD








thiols. After determining the percentage of sulfur present as -SH groups,

the polymer was subjected to oxidative conditions. It was found that

over 95% of the thiols present could be re-oxidized to the disulfide

linkage, thus demonstrating that a rigid polymer matrix can hold func-

tional groups in close proximity.

In the same study, Wulff copolymerized p-vinylbenzyl thioacetate 2

into a macroporous polymer matrix under conditions identical to those

used for monomer 1.14 Reductive cleavage then gave thiols distributed
0

CH2-S CH3






2

randomly over the polymer matrix. Again, the percentage of sulfur pres-

ent as -SH groups was determined, and the polymer was subjected to oxi-

dative conditions. Remarkably, 33% oxidation to disulfide was observed

even for highly cross-linked polymers. Apparently, there is some degree

of chain mobility even in highly cross-linked macroporous polymers.

Wulff and coworkers have also constructed chiral functional cavities

in macroporous polymers and used these polymers in the resolution of race-

mates.15 The copolymerization of a-D-mannopyranoside-2,3; 4,6-di-0-(4-

vinylphenylboronate) 3 containing the chiral template molecule 4 with

varying percentages of cross-linking monomers and monofunctional monomers

was carried out in the presence of an inert diluent. Cleavage of the

chiral template left a chiral cavity containing two boronic acid groups.

The polymers with the highest (95%) cross-linking gave optical enrichments

















OH
0 CH OH

B HO
HO
HO
OR OR



3 i


of up to 87% in the resolution of D- and L-4-nitrophenyl pyranoside,

again demonstrating that a rigid polymer matrix is capable of holding

functional groups together as an active site.

Langenmayr envisioned the construction of these active sites by the

use of a "spacer atom monomer."16 The spacer atom monomer 5 would con-

sist of two functional groups, A and B, joined to each other by a bridge

of spacer atoms denoted "s." The vinyl groups on each end of the spacer

atom monomer would allow it to be incorporated into a rigid styrene/

divinylbenzene copolymer 6. The cleavage of the spacer atoms would then

leave A and B in close proximity on the rigid polymer matrix as shown in

7.

The spacer atoms must be able to withstand the conditions of poly-

merization, yet be cleaved under conditions mild enough not to change

the spatial relationship between A and B.




12












copolymerize-S-S -S -B
/7-A-S-S-S-B- copolymerize> A- -S-S



5 6
cleovoge conditions





L A B




7


The spacer atom monomer synthesized by Langenmayr is shown in

Figure I-9. It contains a benzimidazole and a benzyl alcohol connected

by a carbamate spacer bridge, with acrylamide groups on each end. After

incorporation of this monomer into a macroporous polystyrene/divinylben-

zene matrix, the carbamate bridge was cleaved by treatment with NaH/DMSO

to leave the benzimidazole and benzyl alcohol in close proximity to each

other. Kinetic comparison of this "ordered" polymer with another polymer

in which the same functional groups had been randomly distributed gave a

seemingly anomalous result: the random distribution of the functional

groups gave more efficient solvolytic catalysis of dinitrophenyl benzoate

than did the ordered distribution. Selective blocking of the alcohol








0

NH


Figure I-9. Spacer atom molecule synthesized by Langenmayr.


function on the ordered polymer increased its catalytic efficiency by

50%, leading Langenmayr to propose that hydrogen bonding between the

benzimidazole and the benzyl alcohol in the ordered polymer was actually

decreasing the nucleophilicity of the benzimidazole. Furthermore, Lan-

genmayr calculated that only 5% of the functional sites were actually

active in catalysis.

Discussion

Catalysts based on a rigid polymeric matrix potentially offer several

distinct advantages over catalysts based on flexible linear polymers.

Cross-linked polymers are insoluble in most media and are therefore

easily separated from the products after the reaction. A rigid polymer








matrix can contain chiral functional cavities which allow the catalyst to

recognize and act on a single enantiomer of a racemic substrate. Non-

random cooperation between functional groups in catalysis is possible

since the groups are held in close proximity.

The use of a rigid polymeric matrix in the construction of catalysts

has two main drawbacks: access to the catalytic sites may be limited, and

detailed characterization of the polymer is problematic. The design of

the polymer and the types of reactions to be performed in the construc-

tion of active sites must therefore be chosen carefully.

Macroporous gelular resins are capable of providing a rigid matrix

and maximizing site access. Studies by Millar and coworkers showed that

macroporous styrene-divinylbenzene copolymers of high cross-link density

had higher solvent regain and shorter swelling time than conventional

resins of the same cross-link density. The porous nature of the poly-

mer network is brought about by diluting the monomers during the polymer-

ization. The solvent used must be inert to the reaction conditions and

must be one in which the growing polymer chains are very soluble. Under

such conditions, the polymer chains are solvated throughout the polymer-

ization and become less entangled. Removal of the diluent after poly-

merization leaves a porous network capable of taking up solvents which do

not normally swell cross-linked polystyrene (such as water).

The ability of macroporous resins to take up water is essential to

obtaining high access to catalytic sites. Although Langenmayr calculated

only 5% accessibility to the active sites on his polymers, more recent

results on other catalysts based on macroporous polymers show access to
18
be in the 30-40% range. Regen has shown that catalysts based on macro-

porous polymers are capable of catalyzing reactions by bringing reactants








from aqueous and organic phases together.19 Wittig reagents bound to

macroporous polystyrene have been shown to give high yields of olefins

with a variety of carbonyl substrates in THF/DMSO.20 Thus, it appears

that the problem of access to active sites in highly cross-linked poly-

mers can be overcome by using a macroporous polymeric matrix.

The most direct approaches to the characterization of macroporous

polymers are elemental analysis and infrared spectroscopy. Therefore,

reactions to be performed in the construction of active sites must be

known to proceed in high yield with no side reactions. One must realize

that reaction conditions that are efficient on model compounds in solu-

tion may not be efficient on the macroporous polymer, and that reaction

conditions could conceivably change the macroporous structure of the

polymers.

Proposal of Research

Although Langenmayr's research indicated that macroporous copoly-

(styrene-divinylbenzene) gave very low (ca. 5%) access to the active

sites, this problem has been at least temporarily solved.16'18'20

Esterolytic catalysts based on macroporous copoly(styrene-divinylbenzene)

now typically give 20-40% access. With this in mind, it seemed appro-

priate to concentrate on choosing a proper functional group combination

for cooperative catalysis and finding a way to introduce it onto a macro-

porous polymer.

The combination of imidazole or benzimidazole with an oxygen nucleo-

phile has received considerable attention in soluble linear polymeric

catalysts.12,13 Langenmayr's macroporous polymeric catalyst incorporated

a benzimidazole and a benzyl alcohol into the active sites. It was felt

that the lack of a cooperative catalytic effect may have been a result








of the low nucleophilicity of the benzyl alcohol. It was therefore

decided to pair imidazole and/or benzimidazole with a more powerful

nucleophile. The hydroxamate anion is known to be a strong nucleophile

and seemed a logical choice, particularly in view of Kunitake and

Okahata's findings.3

This dissertation reports the synthesis and kinetic investigation

of the first esterolytic catalysts using functional sites comprised of

imidazole or benzimidazole paired with a hydroxamic acid to be based on

a macroporous polymer. Catalysts with these functional groups in

close proximity were prepared. These were kinetically compared to

catalysts containing only one functional group and to catalysts

containing both functional groups introduced randomly onto the polymer.













CHAPTER 2
SYNTHESIS OF MONOMERS AND POLYMERS
Monomers were desired which, after copolymerization into a macro-
porous matrix, could be elaborated to give an imidazole or benzimidazole
group in close proximity to a hydroxamic acid group. Hydroxylamine hydro-
chloride 10 is known to react with N-acylimidazoles 8 to give high yields
of imidazole 11 and hydroxamic acids 13.21 Similarly, N-acylbenzimida-
zoles 9 react with 10 to give benzimidazole 12 and hydroxamic acids 13.
N

N + NH0H-HCI > + R 'NHOH


R H

8 10 II 13

N


O + NH20H-HCI --- + R 'NHOH

R H

9 10 12 13

It seemed, therefore, that the divinyl analogs 14 and 15 should allow
construction of the sought-after functional group sites by a step-wise
procedure involving copolymerization followed by hydroxylamine cleavage.
17








N N

N N




0 0




14 15

For the cleavage reagent, N,O-disubstituted hydroxylamines were

chosen for two reasons: 1) N-substitution hinders the potential Lossen
rearrangement of the product, and 2) 0-substitution blocks any possible
0-acylation. The 0-substituent must, however, be easily removable in a
subsequent step. Although the use of an 0-protected hydroxylamine necess-
sitates a final deprotection step, it gives an unambiguous route to the
hydroxamic acid. This is important in view of the difficulty in charac-
terizing insoluble macroporous polymers. The construction of "active
sites" consisting of an imidazole to a hydroxamic acid group on a macro-
porous matrix thus follows the strategy shown in Figure II-l.
Polymers containing imidazole or benzimidazole groups distributed
randomly with respect to the hydroxamic acid groups were needed for use
in control experiments. The random distribution of these functional
groups could be accomplished by the copolymerization of monomers 16 and
17 or monomers 18 and 19 into macroporous matrices. After the hydroxyl-
amine cleavage and deprotection reactions, the polymers would contain
the functional groups randomly distributed (see Figure II-2).











0 copolymerize


OR' deprotect
--------


Figure II-i.




N

H


Synthetic sequence leading to imidazole/hydroxamic acid
"active sites" on a macroporous polymer. Sequence be-
ginning with monomer 15 is analogous.


N VC)N N
N N

--0 H


16 17 18 19

Monofunctional polymers, that is, polymers containing imidazole,

benzimidazole, or hydroxamic acid groups alone were also needed for

control experiments. Polymers containing only imidazole or benzimida-

zole could be obtained directly by the incorporation of monomers 16 or

18, respectively, into macroporous matrices (see Figure 11-3).


cleovoge
.---... i


-OH







NN N

NN

H =0 copolymerize
H


0 o

16 17



N N

N N

cleovoge deprotect


N"OR' 'I OH


Figure 11-2. Synthetic sequence leading to random distribution of imi-
dazole and hydroxamic acid on a macroporous polymer.
Sequence beginning with monomers 18 and 19 is analogous.

Polymers containing only hydroxamic acid groups would result from

the incorporation of either monomer 17 or 19 into a macroporous cleavage

and deprotection of the hydroxamic acid group (see Figure 11-4).

The above considerations lead to the choice of monomers 14-19 as

target molecules. Of these, 4(5)-vinylimidazole 16 and 5(6)-vinylbenzi-
22,23
midazole 18 have been reported previously.,23 Also known is N-methyl-

O-benzylhydroxylamine hydrochloride 20; this compound was used in the
13
synthesis of polymer-bound hydroxamic acids. Kunitake and Okahata had

also shown that benzyl hydroxamates may be debenzylated in hydrobromic

acid/acetic acid to give the 0-unsubstituted hydroxamic acid. Therefore,

20 seemed a logical first choice as a hydroxylamine cleavage reagent.













copolymerize


H


copolymerize


TO
H


Figure 11-3. Synthetic sequences leading to macroporous polymers con-
taining only imidazole or benzimidazole groups.

Synthesis of Monomers
The synthesis of N-acyl monomers 14, 15, 17 and 19 began with the
conversion of p-chlorostyrene 21 to p-vinylbenzoic acid 22 via the Grignard
24
reaction. Treatment of 22 with thionyl chloride gave p-vinylbenzoyl
25
chloride 23.

The reaction of two equivalents of imidazole 11 with one equivalent
of acid chloride 23 in dry ether led to the formation of N-(p-vinylben-
zoyl)imidazole 17. Benzimidazole 12 was similarly reacted with acid
chloride 23 to give N-(p-vinylbenzoyl)benzimidazole 19.


N

H












0 copolymerize 0


o 0




R R
I I
cleavage 0 N-OR' deprotect ( 0 N-OH


O O



Figure 11-4. Synthetic sequence leading to polymer containing only
hydroxamic acid groups. Sequence starting with monomer
17 is analogous.

Thermal decarboxylation of trans-urocanic acid 24 gave 4(5)-vinyl-
22
imidazole 16. Treatment of vinylimidazole 16 with acid chloride 23
then yielded N-(p-vinylbenzoyl)-4(5)-vinylimidazole 14.
23
The method of Overberger et al. was employed in the synthesis of
5(6)-vinylbenzimidazole, beginning with the formylation of 4-aminophenyl-
ethanol 25 in 88% formic acid to give B-(4-formamidophenyl)ethyl format
26. Nitration of 25 at -23 in 50/50 HN03/H2S04 gave B-(3-nitro-4-
formamidophenyl)ethyl format 27. Catalytic reduction of nitro compound
27 yielded B-(3-amino-4-formamidophenyl)ethyl format 28. Closure of
the heterocyclic ring and saponification of the format ester were




23



effected in boiling water to give 5(6)-(B-hydroxyethyl)benzimidazole 29.

Thionyl chloride converted 29 to 5(6)-(B-chloroethyl)benzimidazole hydro-

chloride 30. Dehydrohalogenation of 30 then gave the desired 5(6)-vinyl-

benzimidazole 18. Reaction of vinylbenzimidazole 18 with acid chloride

23 yielded N-(p-vinylbenzoyl-5(6)-vinylbenzimidazole 15.


NH2


HCO2H
>


NHCHO

SHNO /HSO4

S--OCHO
L OCHO


NHCHO


O NH2 H'
H2 / Pol -C > A / H2O

OH

28






SOCI


H


DT N



H

29






tBuOK
----^


H
H


30








C `OL


15




H


0
O0


CH2NHOCH20 HCI
20


CO H

0


N
H





16



IOX ;N


cl


I) Mg
2) C2>
2) CO2


SOCI
.>


coCI












N


H


II


N
N
H


HOC N

N
I
H


COCI




23


23


COCI


S02




23


v--uum
vacuum


ether


N

N
0

0


ether


23
ether


N
H


















H

18


COCI




23


23


Synthesis and Model Reactions of Hydroxylamine Cleavage Reagents

Benzyl benzohydroxamate 32 was treated with sodium hydride followed

by methyl iodide to give benzyl N-methyl-benzohydroxamate 33.13 Deben-

zylation of 33 in concentrated hydrochloric acid/ethanol gave N-methyl-

0-benzylhydroxylamine hydrochloride 20.3 Model reactions were then

carried out in order to test the usefulness of 20 as a cleavage reagent.
CH3
I
NHOCH20 O N-OCH20

NoH/MeI HCI/EtOH
S-----> eCH NHOCH02HCI
3^- 2~


20


Reaction of excess 20 with N-(p-tolyl)benzimidazole 34 in THF gave

a quantitative yield of benzyl N-methyl(p-tolyl)hydroxamate 35 and benz-

imidazole 12. In view of this result, 20 seemed promising for use as the

cleavage reagent. However, treatment of 33 with 15% hydrobromic acid/

acetic acid gave only very slow debenzylation accompanied by significant

removal of the N-methyl group. Although trimethylsilyl iodide had been


32


01




27





CH3
N 0 N- OCH2~
0 N
20 + THF +
20

H
CH3 CH,
34 35 12


shown to efficiently debenzylate benzyl carboxylates,26 it gave unsatis-
factory results when reacted with 33. Methane sulfonic acid/acetic acid
also failed to remove the 0-benzyl group. These results necessitated the
synthesis of a hydroxylamine cleavage reagent other than 20 which would
lead to a more easily deprotected hydroxamate ester.
It was thought that a p-methoxy substituent on the benzyl group would
ease the removal of the 0-protecting group under mild SN1 conditions.
Such conditions would also tend to leave the N-methyl group intact. Thus,
the synthesis of N-methyl-O-(p-methoxybenzyl)hydroxylamine hydrochloride
44 was begun. The alkylation of ethyl(N-hydroxy)ethanimidate 3827 by
p-methoxy chloride 3928 was carried out according to Markova et al. to
give ethyl N-(p-methoxybenzyloxy)ethanimidate 4029 Mild acidic hydroly-
sis of 40 in ether gave 0-(p-methoxybenzyl)hydroxylamine hydrochloride
4129 Benzoylation of 41 in THF yielded (p-methoxybenzyl)benzohydroxa-
mate 42. Treatment of 42 with sodium hydride followed by methyl iodide
gave (p-methoxybenzyl)-N-methylbenzohydroxamate 43. Debenzoylation of
43 by sodium hydroxide/methanol yielded N-methyl-0-(p-methoxybenzyl)-
hydroxylamine which was isolated as hydrochloride salt 44. Model







CH CI

+


OMe
39


NaOEt /EtOH
--------->---


NN OCH Ar


HCI /HO20
> NHOCH2Ar HCI
ether


41
CH
0 IN-OCH.Ar




43


0 NHOCHzAr
OCOCI



42



1) NaOH/MeOH
> CH NHOCH2Ar HCI
2) HCI/ether


44


Ar = p methoxyphenyl

reactions were then conducted to test the usefulness of 44 as a

cleavage reagent.

It was found that the anion formed by treatment of 44 with n-

butyllithium at -78 easily cleaved N-(p-tolyl)benzimidazole 34 to give

N-methyl-0-(p-methoxybenzyl)-(p-tolyl)hydroxamate 35 and benzimidazole

12. Furthermore, treatment of 35 with methanesulfonic acid/acetic acid

or anhydrous hydrogen fluoride completely removed the p-methoxybenzyl

group in less than six hours to give N-methyl-(p-tolyl)-hydroxamic acid

45. Anhydrous hydrogen fluoride, in particular, is a strongly ionizing

medium conducive to SN1 reaction.30 Therefore, N-methyl-0-(p-methoxy-

benzyl)hydroxylamine hydrochloride 44 was chosen as the cleavage reagent.


OEt

N\OH


38


NoH/ Mel
---













CH3NHOCH2Ar


I) n-BuLi
2) 34


CH3
I
0 N-OCH Ar





CH3

35


CH3SO3H / HOAr



onhydrous HF


CH3
I
O N-OH





CH3

45


Ar = p- methoxyphenyl



Synthesis of Polymers

Monomers 14-19 were copolymerized with styrene and divinylbenzene
(DVB) using azobisisobutyronitrile (AIBN) as the initiator. The poly-
merizations were carried out using 50/50 v/v toluene/acetonitrile (1.1

ml/g monomers) as a diluent at 50 for five days.i5 The compositions
of the monomer mixtures are shown in Tables II-1 and 11-2. The polymers


N

I
H


























1-
0




I-
a)
L








o b
O
*- CO

c E 9=




0r-






4e
c






o
CL


c -

o -
T") o C









0
0

0 E
00

0 E- E




E







H E E


r-
11



CL
Vn
S-
o)
E


00



E cc
Cr0


N Ec '








E
C

4-,










Ae
O
0

Q
r- r--CO
0 0 >

ro
-o
*
E
*r-
N
C

.0 C
a 0a
4- L.-

O i->
C Ein
0
*r-
'

0.
E I

0
r- C
00
e' EE


1-

0

E- C

EE


1-



00
r- C
o 0
E E


N
C N
C
cn < co w
rr co m LO

N I I N
C N Cp C
w) c a>
CO C 0 CO
> CO I >
I I /) I
CO CO C- CO
> > I >
0 0 0
I I C I
Lv) u) O c/
- C- E C


O o
o 0
C0 C0

-1: *1


o on


o CM Rd r-

ko %o %D ko









-4 0 r- t

o ^ CI Cr










i 5-- i 0'
i i *
c\J C
00C Cn


C' C-J


I I I
I I I


0' 03
r- P- oC

C' i CC











II
*

























C-)
1 0


















M
I I
* i i


a)
'a E
00

E o
E E


S-

b- E
0
.- C
0 0
E E








obtained by this procedure are white solids with a chalky appearance

characteristic of macroporous polymers. The copious evolution of air

bubbles that results when small amounts of these polymers are placed in

solvents such as toluene, THF, or aqueous buffers is further evidence
17
of a permanent pore structure. The polymerizations carried out are

shown in Figures 11-5 and 11-6.


14 + styrene + DVB


50/50 CH3CN / toluene
AIBN
50 / 5 days


PS DVB VBVIm 46


16 + 17 + styrene + DVB


some
conditions
conditions


PS DVB -VBIm 47


16 + styrene + DVB


some
conditions
conditions


N



H
mono PS-DVB-Im 48


Figure 11-5. Imidazole-containing macroporous polymers synthesized.











15 + styrene + DVB


50/50 CH3CN / toluene
AIBN
50/5 days


PS- DVB VBVBenz 49


18 + 19 + styrene + DVB


some
conditions
conditions


18 + styrene + DVB







19 + styrene + DVB


some
----------
conditions






some
conditions


PS DVB VBenz VBBenz 50



0>N
H


PS DVB- VBBenz


51









52


Benzimidazole-containing macroporous polymers synthesized.


Figure 11-6.








Polymers 46-52 were characterized by elemental analysis and infra-

red spectroscopy. Since the monomers used in polymers 46, 47, 49, 50,

and 52 contain a carbonyl group, the carbonyl region of the infrared

spectrum is most informative. All of these polymers exhibit a strong
-I
carbonyl band (ca. 1700 cm ) in addition to normal copoly(styrene-divinyl-

benzene) absorptions. No unincorporated monomer was detected by NMR in

the washings of the polymers. Satisfactory elemental analyses were ob-

tained for all polymers 46-52.

Hydroxylamine Cleavage Reaction on Polymers

The hydroxamate ester functionality was incorporated into polymers

46, 47, 49, 50, and 52 by the reaction of these polymers with lithium

N-methyl-0-(p-methoxybenzylhydroxylamide 53. Anion 53 was generated

by treating 1.0 equivalent of disubstituted hydroxylamine salt 44 with

1.9 equivalents of n-butyllithium in THF at -78 under an argon atmos-

phere. The cold solution of the anion was then transferred onto the

Li+
1.9 equiv n-BuLi -L
CHNHOCH2Ar- HCI > CH3NOCH2Ar

44 53
Ar = p- methoxyphenyl

polymer and allowed to slowly warm to room temperature. The hydroxyl-

amine cleavages carried out are shown in Figures 11-7 and 11-8.

Polymers 54-58 were characterized by elemental analysis and infra-

red spectroscopy. Alkyl hydroxamates are known to have a carbonyl ab-
31
sorption at ca. 1630 cm-1 in the infrared spectrum. Comparing the
relative intensities of the carbonyl band at 1700 cm-' (starting material)

with that at 1630 cm-1 (product) gives a qualitative measure of reaction



















46 + 53 >


CH
.N-OCH Ar


ordered PS DVB Im- MHAOCH2Ar 54


-OCHAr


47 + 53


random PS DVB -Im- MHAOCH2Ar 55









Ar = p methoxyphenyl

Figure 11-7. Hydroxylamine cleavages carried out on imidazole-
containing macroporous polymers.














49 + 53 --


I-OCH2Ar


ordered PS DVB Benz MHAOCH2Ar


-OCH2Ar


50 + 53 >


random PS- DVB Benz MHAOCH Ar


I- OCH2Ar


52 + 53 -


mono PS-DVB-MHAOCH2Ar


Ar = p- methoxyphenyl


Figure 11-8.


Hydroxylamine cleavage reactions carried out on benzimi-
dazole-containing polymers.


56







yield. Since the carbonyl absorption at 1700 cm" has nearly disappeared

in all polymers 54-58, the hydroxylamine cleavage reaction apparently

proceeds in high yield. Elemental analyses (with theory based on 100%

reaction) were satisfactory in all cases.

Dealkylation of Polymer Bound Hydroxamate Ester

Polymers 54-58 required the removal of the O-(p-methoxybenzyl)

substituent in order to generate polymer-bound hydroxamic acid. Anhy-

drous hydrogen fluoride (HF) was shown to remove this 0-substituent easily

on model monomeric systems. Since HF has been shown to be effective in

the somewhat analogous application of cleaving peptides from solid-phase
30
synthesis resins, it seemed a good choice of reagent.

The reactions shown in Figure II-9 were carried out. Polymers

54-58 were treated with anhydrous HF at room temperature for 24 hours.

The products of these reactions, polymers 59-63, were characterized by

infrared spectroscopy and elemental analysis.










54










55











56










57







58


onhydrous HF
room temp / 24 h









some
conditions









same
---------^
conditions








same
------^
conditions






some
conditions


ordered PS DVB -


Benz MHA 61
CH3
-N-OH


random PS DVB Benz MHA


62


mono PS- DVB- MHA


Figure 11-9.


Removal of the O-(p-methoxybenzyl) substituent on poly-
mers 54-58.


- Im MHA 59

CH
.N-OH





Im MHA 60













CHAPTER 3

KINETIC EVALUATION OF POLYMER CATALYSTS

Introduction

Most of the functionalized polymers synthesized for use as

nucleophilic catalysts have been soluble in aqueous reaction media.

In general, the catalytic efficiency has been determined by observing

the ability of these polymers to catalyze the hydrolysis of activated

esters such as p-nitrophenylacetate. Such reactions are easily

followed spectrophotometrically.

The catalysts synthesized in this study are based on highly cross-

linked macroporous polymers. Such polymers are insoluble; therefore,

these catalysts must be studied in a heterogeneous system. Several

difficulties arise in the study of heterogeneous systems. There is

the potential for difficulty in measuring reaction rates. The

kinetics of heterogeneous systems are often less reproducible than

those of homogeneous systems since it is difficult to reproducibly

construct a solid-phase catalyst.33 The concentration of substrate in

the interfacial region where reaction occurs is difficult to observe.

Heterogeneous systems are often stirred in order to lessen the impact of

diffusion processes on the rate. However, the macroporous polymers

synthesized for this investigation are quite brittle, and constant

stirring leads to particle fragmentation. Another problem is the effect

of the polymer matrix on a bound functional group. A functional group

which catalyzes a homogeneous reaction may or may not still catalyze the

38








reaction when bound to a polymer. It is possible that the environ-

ment of the polymer may enhance the reactivity of some functional groups

while retarding the reactivity of others.

Preliminary Experiments

In order to assess the effect of the polymer matrix on the

catalytic ability of a bound functional group, the mono-functional

polymers were kinetically compared with soluble monomeric analogs.

Pseudo first order rate constants for the hydrolysis of dinitro-

phenylbenzoate(DNPB) and p-nitrophenylacetate(PNPA) by imidazole,

benzimidazole, and N-methyl-(p-tolyl)hydroxamic acid were determined.

These were compared with the pseudo first order rate constants for the

same reactions in the presence of mono-PS-DVB-VIM 48, mono-PS-DVB-

VBenz 51, and mono-PS-DVB-MHA 63. These results are shown in Tables

III-1 through III-4.


Table III-1. Pseudo first order rate constants for the hydrolysis
of DNPB in the presence of mono-functional polymeric catalysts and
soluble analogs.

catalyst kcat x 105(sec'-) no. runs

imidazole 16.4 0.5 3

mono-PS-DVB-VIm 26.2 1.0 3

benzimidazole 1.96 0.06 3

mono-PS-DVB-VBenz 14.9 0.2 3

N-methyl-(p-tolyl)hydroxamic acid 138. 7. 3

mono-PS-DVB-MHA 20.2 0.7 3

pH 7.00, phosphate buffer, 25C, 37.5% (v/v) CH3CN, kspon x 105 (sec-1)
= 0.15, 3.00 x 10-6 = moles polymer-bound catalyst =
[soluble catalyst] X liters solution.




40



Table III-2. Pseudo first order rate constants for the hydrolysis
of DNPB in the presence of mono-functional polymeric catalysts and
soluble analogs.


catalyst


imidazole


kcat x 105 (sec-')

23.2 1.1


no. runs


mono-PS-DVB-VIM

benzimidazole


mono-PS-DVB-VBenz

N-methyl-(p-tolyl)hydroxamic acid


mono-PS-DVB-MHA


38.4 1.4

2.41 + 0.08

17.9 + 0.7

68.8 + 2.5

22.4 0.8


pH 8.18 collidine-HC1 buffer, 25C, 37.5%
= 0.32, 3.00 x 10-6 = moles polymer-bound
[soluble catalysts] X liters solution.


(v/v) CH3CN, kspon
catalyst =


x 105(sec-1)


Table III-3. Pseudo first order rate constants for the hydrolysis
of PNPA in the presence of mono-functional polymeric catalysts and
soluble analogs.


kcat x 105(sec-1)

0.00


no. runs


mono-PS-DVB-VIM

benzimidazole

mono-PS-DVB-VBenz


8.91 0.28


0.00

0.00


N-methyl-(p-tolyl)hydroxamic acid 62.2 2.7


mono-PS-DVB-MHA


6.94 0.2


pH 8.00 TRIS-HC1 buffer, 250C, 38.0% (v/v)ethanol, kspon x 105(sec-1)
= 2.09, 3.00 x 10-6 = moles polymer-bound catalyst
[soluble catalyst] X liters solution


catalyst


imidazole








Table 111-4. Pseudo first order rate constants for the hydrolysis
of PNPA in the presence of mono-functional polymeric catalysts and
soluble analogs.

catalyst kcat x 105(sec-1) no. runs

imidazole 27.7 1.0 2

mono-PS-DVB-VIM 11.7 0.4 2

benzimidazole 0.00 2

mono-PS-DVB-VBenz 0.00 2

N-methyl-(p-tolyl)hydroxamic acid 129. 4. 3

mono-PS-DVB-MHA 0.00 2

pH 9.00 TRIS-HC1 buffer, 25C, 28.9 (v/v)ethanol, kspon x 105(sec-1) =
14.8, 3.00 x 10-6 = moles polymer-bound catalyst =
[soluble catalyst]


It is apparent from the data in Tables III-1 through III-4 that

polymer-bound imidazole and benzimidazole are, in the cases studied,

more effective catalysts for the hydrolysis of DNPA and PNPA than

soluble analogs imidazole and benzimidazole. Polymer-bound imidazole

exhibits about a 1.5-fold rate enhancement relative to imidazole in

the phosphate and collidine buffers studied. Polymer-bound benzimidazole

gives about a 7.5-fold rate enhancement relative to benzimidazole in

these buffers. These rate enhancements are uncorrected for active

site accessibility on the polymers. Therefore, they represent a

conservative estimate of the increased catalytic ability of these

functional groups when bound to a polymer. That the binding of

these functional groups to a macroporous polymer results in increased

catalytic activity can be explained as the result of two factors: 1) the

polymer matrix effectively increases the substrate concentration in the

vicinity of the functional groups, and 2) the polymer matrix provides

a favorable environment for the nucleophilic catalysis by these







heterocycles to take place. Langenmayr has shown that DNPB

rapidly and quantitatively concentrated on the surface of macroporous

copoly(styrene-divinylbenzene) when introduced into a mixture composed

of a polar solvent and the hydrophobic polymer.16 The polymer-bound

imidazole or benzimidazole, capable of reacting as a neutral nucleo-

phile, reacts readily with the substrate on the surface of the poly-

mer.

The polymer-bound hydroxamic acid is much less effective as a

catalyst for the hydrolysis of DNPB and PNPA than hydroxamic acid in

solution (see Tables III-1 through III-4). Polymer-bound hydroxamic

acid in exhibits a 3-fold to 10-fold decrease in rate relative to

soluble analog N-methyl-(p-tolyl) hydroxamic acid. Apparently, the

positive effect of increasing the concentration of substrate in the

vicinity of the functional groups is overcome by the unfavorable

environment for nucleophilic catalysis by the hydroxamate anion. Since

the hydroxamate anion must be the catalytic specie13, there are two

possible explanations for this lack of reactivity: 1) the pka of the

hydroxamic acid is increased when bound to a polymer, and/or 2) the

reactivity of the hydroxamate anion itself is lowered when bound to a

polymer. Determination of the pka of the macroporous polymer-bound

hydroxamic acid by standard titration is not feasible. The high

crosslink density of the polymer practically assures that the pH

in the polymer will be different from the pH in the bulk solution and

that these will be very slow to equilibrate.34 Kunitake and Okahata's

soluble polymers did allow for titration of a polymer-bound hydroxamic

acid.13 The pka observed for the polymer-bound acid was ca. 10.5,








compared with a pka for the free hydroxamic acid of ca. 8.5. If

the pka of the hydroxamic acid is increased in the polymer environ-

ment, the lowered reactivity is explainable as the result of fewer

hydroxamate anions being available for catalysis. The hydroxamate

anion, once formed, may be less nucleophilic in the polymer environ-

ment than in solution. This also would explain the lowered reactivity

of the polymer-bound hydroxamic acid.

A simple experiment was performed to determine what effect

blank (i.e., non-functionalized) macroporous copoly(styrene-divinyl-

benzene) has on the imidazole-, benzimidazole-, and N-methyl-(p-tolyl)-

hydroxamic acid-catalyzed hydrolysis of DNPB. The results are shown

in Table III-5.

Table III-5. The effect of blank polymer on the pseudo first order
rate constants for imidazole-, benzimidazole-, and N-methyl-(p-tolyl)-
hydroxamic acid-catalyzed hydrolysis of DNPB.

catalyst Polymer present kcat x 10s(sec-1) no. runs

imidazole no 16.4 0.6 2

yes 18.7 0.7 2

benzimidazole no 1.96 0.07 2

yes 2.74 0.12 2

N-methyl-p(tolyl)
hydroxamic acid no 138. 2. 3

yes 101. 1. 3

pH 7.00 phosphate buffer, 25C, 37.5% (v/v) CH3CN, kspon x 105(sec-1)
= 0.15, 1.00 x 10-3 = [catalyst].

Care must be taken in interpreting the results of this experiment, as

the catalysts are certainly concentrated in the polymer to varying

degrees. However, the trends evident in Table III-5 are consistent







with those in Table III-1. The catalytic ability of imidazole

and benzimidazole are enhanced in the presence of the macroporous

polymer. This is apparently the result of the binding of both

catalyst and substrate on the polymer surface. The catalytic ability

of the hydroxamic acid is decreased when the polymer is present. The

substrate may be differentially concentrated in the polymer and thus

not able to react as readily with hydroxamic acid in solution. Altern-

atively, both catalyst and substrate may concentrate in the polymer,

with the polymer environment retarding the catalytic ability of the

hydroxamic acid.

The primary purpose of this investigation was to synthesize

bifunctional polymers which would demonstrate cooperative effects

in the nucleophilic catalysis of ester hydrolysis. This requires

a balance of nucleophilicity between the cooperating functional

groups. Ideally, one would like to couple a strong nucleophile (e.g.,

hydroxamate ion) with a weaker nucleophile (e.g., imidazole or

benzimidazole). Such a bifunctional system should give fast

acylation and deacylation (see Equations 3 and 4, Chapter 1).

Anything that upsets this balance of nucleophilicity will lower the

probability of observing cooperative catalytic effects. Since

binding the hydroxamic acid to a macroporous polymer drastically

lowers its catalytic activity, the "strong" nucleophile is not

available for the functional group pair. Therefore, the probability

of observing cooperative catalysis in the systems synthesized is

lowered.








Kinetic Comparison of Ordered and
Random Bifunctional Polymers

Pseudo first order rate constants for the hydrolysis of DNPB

and PNPA by ordered PS-DVB-Im-MHA 59, random PS-DVB-Im-MHA 60,

ordered PS-DVB-Benz-MHA 61, and random PS-DVB-Benz-MHA 62 are

shown in Tables III-6 through III-9.


Table III-6. Pseudo first order rate constants for the hydrolysis
of DNPB in the presence of ordered and random bifunctional polymeric
catalysts.

catalyst kcat x 105(sec-1) no. runs

ordered PS-DVB-Im-MHA 59 26.0 0.8 2

random PS-DVB-Im-MHA 60 26.6 1.1 2

ordered PS-DVB-Benz-MHA 61 26.3 1.1 2

random PS-DVB-Benz-MHA 62 29.8 0.9 2

pH 7.00 phosphate buffer, 25C, 37.5% (v/v) CH3CN, kspon x 105(sec-1)
= 0.15, 3.00 x 10-6 = moles polymer-bound catalyst =
[soluble catalyst] X liters solution.


Table III-7. Pseudo first order rate constants for the
DNPB in the presence of ordered and random bifunctional
catalysts.

catalyst kcat x 105(sec'1)

ordered PS-DVB-Im-MHA 59 27.2 1.3

random PS-DVB-Im-MHA 60 25.4 1.1

ordered PS-DVB-Benz-MHA 61 25.1 1.0

random PS-DVB-Benz-MHA 62 24.2 1.2

pH 8.18 collidine-HC1 buffer, 25C, 37.5% (v/v) CH3CH,
(sec-1) = 0.32, 3.00 x 10-6 = moles polymer-bound catal
= [soluble catalyst] X liters solution.


hydrolysis of
polymeric


no. runs

2

2

2

2

kspon x 105
yst








Table III-8. Pseudo first order rate constants for the hydrolysis
of PNPA in the presence of ordered and random bifunctional polymeric
catalysts.

catalyst kcat x 105 (sec"') no. runs

ordered PS-DVB-Im-MHA 59 11.8 0.5 2

random PS-DVB-Im-MHA 60 16.2 0.6 2

ordered PS-DVB-Benz-MHA 61 8.97 0.33 2

random PS-DVB-Benz-MHA 62 10.4 0.4 2

pH 8.00 TRIS HC1 buffer, 25C, 28.9% (v/v)ethanol, k x 10(sec-1)
= 2.09, 3.00 x 10-6 = moles polymer-bound catalyst spoon
[soluble catalyst] X liters solution.


Table III-9. Pseudo first order rate constants for the hydrolysis
of PNPA in the presence of ordered and random bifunctional polymeric
catalysts.

catalyst kcat x 10s(sec-1) no. runs

ordered PS-DVB-Im-MHA 59 7.20 0.26 2

random PS-DVB-Im-MHA 60 11.6 0.6 2

ordered PS-DVB-Benz-MHA 61 2.66 0.08 2

random PS-DVB-Benz-MHA 62 3.63 + 0.14 2

pH 9.00 TRIS-HC1 buffer, 25C, 28.9% (v/v)ethanol, kspon x 105(sec-1)
= 14.8, 3.00 x 10-6 = moles polymer-bound catalyst
[soluble catalyst] X liters solution.


From Tables III-6 through III-9 it is apparent that there is no signif-

icant difference in catalytic ability between the ordered and random

bifunctional polymers; therefore, there are no demonstrable

cooperative catalytic effects. There are several possible reasons

for the lack of an observable cooperative effect. The most obvious

reason is that the catalytic ability of hydroxamic acid is ad-

versely affected by the macroporous polymer environment. However,

there is evidence that the surface of a highly crosslinked macroporous







polymer is covered with a layer of low crosslink density. If

this is so, there may be enough conformational mobility to allow

the "ordered" functional groups to move away from each other.

Another possibility is that getting functional groups in "close

proximity" may not be sufficient to allow for cooperative catalysis.

It may be necessary to design a monomer by which a definite stereo-

chemical relationship between the functional groups can be established.


Burst Kinetics

The use of p-nitrophenylacetate (PNPA) as a substrate for

chymotrypsin helped elucidate the mechanism of catalysis.35'36 The

reaction, when run with a large excess of PNPA, was found to be

biphasic in nature. An initial rapid release (burst) of

p-nitrophenol (PNP) was followed by a slower steady-state release

of PNP as shown in Figure III-1. The biphasic nature of the reaction





Intercept=R


absorbance


A=Re-bt



time
Figure III-1. Burst kinetics of the a-chymotrypsin catalyzed
hydrolysis of PNPA.

implies two steps, and hence implies the existence of an intermediate.

Equation 5 shows enzyme (E) and substrate (S) binding to form an enzyme-







substrate complex (ES). In this complex the enzyme and substrate

react to form an acyl-enzyme intermediate (ES') and release the

alcohol fragment of the substrate (P1). The acyl-enzyme inter-

mediate is subsequently hydrolyzed to regenerate the enzyme and

release the carboxylic acid portion of the substrate (P2). The kinetics

are explained by the rapid acylation of the enzyme

E + S ES ---- ES' + P1 ---> E + P2 (5)

liberating a burst of PNP, followed by a slower release of PNP which

is dependent on the rate of deacylation of the acyl-enzyme inter-

mediate. More information can be obtained from Figure III-1. The

y-intercept, R, gives a direct measure of the enzyme concentration.

The slope, Q, and the constant, b, may be used to calculate the rates

of acylation and deacylation.

Observation of burst kinetics is evidence that an intermediate

exists along the reaction path and rules out a mechanism by which the

catalyst acts exclusively as a general base. All of the catalysts

synthesized in this investigation exhibit burst kinetics. Recall that

determination of the y-intercept, R, in Figure III-1 gives a direct

measure of the enzyme concentration. The intercept actually corresponds

to the concentration of active sites. For enzymes with one active site

per molecule, the concentration of active sites is equal to the

concentration of the enzyme. The catalysts synthesized in this study

have many active sites per polymer particle. However, a similar

analysis of the burst kinetics should lend itself to the assessment

of the number of kinetically active sites per specific weight

of polymer. This, in turn, can be used to calculate the






percentage of polymer-bound functional groups that are kinetically

accessible. Burst kinetic runs were performed on mono PS-DVB-IM 48,

mono PS-DVB-Benz 50, ordered PS-DVB-Benz-MHA 61, random

PS-DVB-Benz-MHA 61, random PS-DVB-Benz-MHA 62, and mono PS-DVB-MHA 63.

The polymer was carefully weighed into a cuvet and the run was

performed. Absorbance due to background hydrolysis was subtracted

out. The value of the y-intercept, R, in absorbance units, was

converted to concentration units by a Beer's Law plot. Multiplying

this concentration by the volume of solution in the cell (3.00ml)

gave the number of moles of kinetically active functional groups on the

polymer. Comparison of this number with the theoretical number of

functional groups incorporated into the polymer then gives the

percentage of kinetically accessible functional groups. The results

are shown in Table III-10.


Table III-10. Accessibility of functional groups on macroporous
copoly(styrene-divinylbenzene) determined by burst kinetics.

catalyst % access

mono PS-DVB-Im 48 36.3

mono PS-DVB-Benz 50 28.8

ordered PS-DVB-Benz-MHA 61 33.1

random PS-DVB-Benz-MHA 62 43.7

mono PS-DVB-MHA 63 19.7


It should be noted that for mono-PS-DVB-MHA 63, the steady state

portion of the burst curve had a slope of zero. This indicates that

the deacylation step is immeasurably slow, consistent with Kunitake and

Okahata's findings.13 All other polymers gave burst curves with a







positively sloped steady state portion. For most polymers, the

percentage of accessible functional groups varies over a fairly

narrow range of between 30-40%. Mono PS-DVB-MHA 63 gave only 19.7%

access. This slightly lower access is not, however, sufficient to

explain the low catalytic ability of polymer-bound hydroxamic acid

relative to hydroxamic acid in solution.



Conclusion

This investigation has demonstrated an ability to place catalytic

functional groups on a highly crosslinked macroporous polymer and

have a useful percentage of them remain kinetically accessible. In

the cases of imidazole and benzimidazole, the polymer-bound functional

group was found to have increased catalytic ability relative to

soluble analogs. However, binding a hydroxamic acid function to the

polymer resulted in lowered catalytic ability relative to its soluble

analog. These differing effects of the polymer environment on bound

functional groups upset the balance of reactivity necessary to observe

cooperative catalytic effect. The observation of burst kinetic

behavior for all catalysts synthesized is evidence for their action as

nucleophilic catalysts for esterolysis.













CHAPTER 4

EXPERIMENTAL PROCEDURE

Introduction

Melting points are recorded in degrees Centigrade and are uncor-

rected. Melting points were determined with a Thomas-Hoover Unimelt

capillary melting point apparatus. Infrared spectra were recorded on a

Perkin-Elmer 283-B infrared spectrophotometer. Nuclear magnetic resonance

spectra were recorded on a Varian EM-360 spectrometer. All chemical

shifts (6) are recorded in parts per million (ppm) downfield from tetra-

methylsilane as an internal reference. Low resolution mass spectra,

exact mass, and molecular weight data were measured on an AEI-MS-30 double

beam mass spectrometer. Microanalyses were carried out by Atlantic Micro-

lab, Inc., Atlanta, Georgia. Solvent evaporation was performed at reduced

pressure on a Buchi Rotavapor-R rotary evaporator equipped with either a

water aspirator or mechanical vacuum pump. A Perkin-Elmer 330 spectro-

meter was used for UV-visible absorbance measurements. The pH measure-

ments were made with a Beckman Research pH meter equipped with a

Radiometer GK 2321C electrode. Polymers were weighed for kinetic runs

on a Cahn 29 Automatic Electrobalance.

Syntheses

N-(p-Vinylbenzoyl)-4(5)-vinylmidazole (14)

In 5 ml of dry ether, 4(5)-vinylimidazole 16 (0.21 g, 2.2 mmol) was

partially dissolved. The mixture was cooled to 0OC. A solution of p-

vinylbenzoyl chloride (0.08 g, 1.1 mmol) in 3 ml dry ether was added dropwise

51







over 15 minutes. The resulting precipitate was filtered. The solvent

was removed from the filtrate under reduced pressure to leave a color-

less oil, which was freeze-dried overnight to give 0.22 g (93%) product

as a white powder: mp 37-39"C, nmr (CDC13) 6 5.00-6.27 multiplee, 4H),

6.50-7.60 multiplee, 3H), 7.67-8.1 (quartet, 4H), 8.33 (singlet, 1H);

ir (CHBr3 soln) cm-1 900, 1190, 1240, 1300, 1370, 1466, 1605, 1705.

N-(p-Vinylbenzoyl)-5(6)-vinylbenzimidazole (15)

In 5.0 ml dry ether, 5(6)-vinylbenzimidazole 18 (0.25 g, 0.0017 mol)

and triethylamine (0.265 ml, 0.193 g, 0.0019 mol) were dissolved and the

solution was cooled to 00C. In 3.0 ml dry ether p-vinylbenzoyl chloride

(0.289 g, 0.0017 mol) was added dropwise over 15 minutes. The reaction

mixture was then allowed to warm to room temperature and was stirred an

additional 15 minutes. Hydrochloric acid (5% solution, 5 ml) was added

with stirring. The ethereal layer was separated and washed sequentially

with 5% K2C03 and water. After drying (MgS04) and filtering, the ethereal

layer was evaporated under reduced pressure to give a white solid. Re-

crystallization (benzene/cyclohexane) gave 0.20 g (41.3%) product: mp 118-

120C, nmr (CDC13) 6 5.30-6.20 multiplee, 4H), 6.60-7.25 multiplee, 2H),

7.40-8.10 multiplee, 7H), 8.30 (singlet, 1H); ir (CHBr3 soln) cm"1 905,

990, 1180, 1195, 1300, 1355, 1700.

Anal. Calcd. for C18HisN20: C, 78.81; H, 5.14; N, 10.21.

Found: C, 78.65; H, 5.17; N, 10.09.

4(5)-Vinylimidazole (16)

Urocanic acid (5.0 g, 0.053 mol) was heated in a Kugelrohr apparatus

under vacuum. At a temperature of 220C, the material melted and began

to decompose. The product distilled as a colorless oil (bp 120C, 0.3

mm Hg) which crystallized on standing to give 1.8 g (53%) white solid:







mp 82-84oC, lit22 mp. 83.2-84.5"C; nmr (CDCl3) 6 5.20 doublett, of doub-

lets, 1H), 5.73 doublett of doublets, 1H), 6.10 (quartet, 1H), 7.17 (sing-

let, 1H), 7.77 (singlet, 1H).

N-(p-Vinylbenzoyl)imidazole (17)

Imidazole (0.51 g, 7.6 mmol) was partially dissolved in 10 ml dry

ether. The mixture was cooled to 0OC. A solution of p-vinylbenzoyl

chloride (0.63 g, 3.8 mmol) in 7 ml dry ether was added dropwise over 15

minutes. The resulting precipitate was filtered. The solvent was removed

from the filtrate under reduced pressure to leave a colorless oil, which

was freeze-dried overnight to give 0.68 g (90%) product as a white powder:

nmr (CDC13) 6 5.27 doublett, 1H), 6.12 doublett, 1H), 6.77-7.27 doublett

of doublets, 1H), 7.40 (singlet, 1H), 7.33-8.10 multiplee, 5H), 8.33

(singlet, 1H); ir (CHBr3 soln) cm-' 900, 1194, 1230, 1295, 1377, 1466,

1605, 1705.

5(6)-Vinylbenzimidazole (18)

Potassium (5.20 g, 0.13 mol) was dissolved in 100 ml of dry t-butanol

under a dry nitrogen atmosphere. Using a solid addition funnel 5(6)-

(B-chloroethyl)benzimidazole 30 (4.40 g, 0.020 mol) was added in two

portions over 10 minutes. The reaction mixture was stirred at room tem-

perature for 20 hours, then neutralized with glacial acetic acid. The

solvent was removed at room temperature under reduced pressure. The re-

sulting residue was partitioned between methylene chloride and water. The

pH of the water layer was then adjusted to pH 8.0, after which the aqueous

layer was extracted with 4 x 50 ml methylene chloride. The combined

organic extracts were dried (MgSO4), filtered, and evaporated to give a

brown oil. Trituration of the oil in ether gave 2.10 g (71%) product:

mp 110-111C, lit23 mp 115-116*C; nmr (CDC1 ) 6 5.25 doublett of doublets,








1H), 5.85 doublett of doublets, 1H), 6.90 doublett of doublets, 1H),

7.30-7.80 multiplee, 3H), 8.2 (singlet, 1H); ir (Nujol mull) cm"- 910,

990.

N-(p-Vinylbenzoyl)benzimidazole (19)

Benzimidazole (0.14 g, 0.0012 mol) and triethyl amine (0.184 ml,

0.134 g, 0.0013 mol) were stirred as a slurry in 2.ml ether at 00C.

In 2. ml ether p-vinylbenzoyl chloride (0.20 g, 0.0012 mol) was added

dropwise with stirring. The reaction mixture was then allowed to warm to

room temperature and was stirred an additional 15 minutes. The reaction

mixture was partitioned between ether and water, and the ether layer was

washed sequentially with 5% HC1, 5% K2C03, and water. The ether layer

was dried (MgS04) and evaporated to give 0.29 g (100%) product as fluffy

needles: mp 111-113"C; nmr (CDC13) 6 5.53 doublett, 1H), 6.00 doublett,

1H), 6.90 (quartet, 1H), 7.33-8.03 multiplee, 8H), 8.33 (singlet, 1H);

ir (CHBr3 soln) cm-1 745, 752, 908, 1290, 1355, 1450, 1610, 1700.

Anal. Calcd. for C16H12N20: C, 77.38; H, 4.88; N, 11.28.

Found: C, 77.29; H, 4.90; N, 11.27.

N-Methyl 0-Benzyl Hydroxylamine Hydrochloride (20)

Benzyl N-methylbenzohydroxamate 33 (5.9 g, 24. mmol) was dissolved

in 40. ml ethanol and 50. ml concentrated hydrochloric acid. The solution

was refluxed for 25 minutes. The solution was diluted with 65. ml of

water and, while still warm, extracted with benzene. The aqueous layer

was evaporated under reduced pressure to give a white solid. Recrystalli-

zation (ethanol) gave 3.0 g (83%) white needles: mp 93-95C, lit13 mp

95C; nmr (dmso-d6) 6 2.83 (singlet, 3H), 5.07 (singlet, 2H), 6.93-7.50

multiplee, 5H).







p-Vinylbenzoic Acid (22)

Magnesium turnings (0.97 g, 0.040 mol) were ground with a mortar and

pestle and placed in a 3-necked 50 ml round bottom flask equipped with

magnetic stirrer, mechanically driven syringe, reflux condenser, and dry

N2 inlet. A solution of p-chlorostyrene (5.0 g, 0.036 mol) in 10 ml dry

THF was placed in the syringe. After the magnesium was activated with a

small amount of methyl iodide, the p-chlorostyrene solution was added

over a four hour period. During the addition gentle heating was applied

with a heating mantle. When the magnesium had been consumed, the reaction

mixture was poured onto crushed dry ice. Sulfuric acid (15% solution, 10

ml) was poured onto the mixture. The product solidified and was filtered.

Recrystallization (20% ethanol) yielded 3.5 g (66%) product: mp 140-142*C,

lit24 mp 138-142C; nmr (CDC13) 6 5.55 doublett, 1H), 5.80 doublett, 1H),

6.85 doublett of doublets, 1H), 7.80 (quartet, 4H), 10.10 (broad hump,

1H); ir (CHBr3 soln) cm-1 780, 860, 1140, 1285, 1420, 1690, 2800-3000

(broad).

p-Vinylbenzoyl Chloride (23)

At 0OC, p-vinylbenzoic acid 22 (0.50 g, 0.0034 mol) was added to

1.0 ml thionyl chloride with stirring. A reflux condenser was set up and

the solution was refluxed gently for one hour. The excess thionyl chloride

was evaporated under reduced pressure to give a brown oil. Bulb-to-bulb

distillation (1500-160*C, 5 mm Hg, lit25 bp 69.5-70.0C, 0.1 mm Hg) gave

0.48 g (84.9%) product as a colorless liquid: nmr (CDC13) 6 5.45 doublett,

1H), 5.87 doublett, 1H), 6.77 doublett of doublets, 1H), 7.77 (quartet,

4H); ir (neat) cm-1 667, 850, 870, 1405, 1605, 1740, 1770.








B-(4-Formamidophenyl)ethyl Formate 26

Recrystallized (ethanol) 4-aminophenylethanol 25 (28.0 g, 0.20 mol)

was refluxed in 100 ml 88% formic acid for 2 hours. The solvent was

then removed under reduced pressure. The resulting dark oil was stirred

in ether overnight to give a white solid. The solid was filtered and

washed with ether: 25.2 g (64%) mp 77-79C; lit23 mp 78.5-79C, nmr

(CDC13) 6 2.95 (triplet, 2H); 4.38 (triplet, 2H); 7.00-7.60 multiplee,

4H); 8.02 (singlet,1H); 8.30 (singlet, 1H); 8.67 (singlet, 1H); ir (CHBr3

soln) cm-1 1140, 1410, 1517, 1610, 1690, 1715.

B-(3-Nitro-4-formamidophenyl)ethyl Formate (27)

In 100 ml of a 50/50 v/v mixture of concentrated HNO3/concentrated

H2SO, at -23C, B-(4-formamidophenyl)ethyl format 26 (11.0 g, 0.057 mol)

was nitrated. Small portions of 26 were added to the acid over one-half

hour. The mixture was then stirred an additional 15 minutes. The reac-

tion mixture was poured into 750 ml ice water. The resulting precipitate

was filtered and washed with water until acid-free. Recrystallization

(ethanol) gave 6.0 g (44%) product as yellow needles: mp 117-119C, lit23

mp 118-119C; nmr (CDC13) 6 3.10 (triplet, 2H), 4.41 (triplet, 2H), 7.23-

8.19 multiplee, 3H), 8.60 (singlet, 1H), 8.80 (singlet, 1H), 10.26 (broad

hump, 1H); ir (CHBr3 soln) cm-1 1375, 1535, 1710, 1720, 3300.

B-(3-Amino-4-formamidophenyl)ethyl Formate (28)

In 200 ml of 50/50 v/v dioxane/ethanol 6-(3-nitro-4-formamidophenyl)-

ethyl format 27 (12.0 g, 0.050 mol) was partially dissolved and 0.5 g 10%

palladium-on-carbon was added. The mixture was degassed and placed under

60 psi of hydrogen in a Parr hydrogenator. After shaking overnight the

hydrogen pressure was constant. The catalyst was removed by filtration

through Celite, and the solvent was evaporated under reduced pressure to







give 10.5 g (100%) product which was not purified further: mp 110-1130C,

lit23 mp 127-128OC; nmr (dmso-d6) 6 2.75 (triplet, 2H), 4.20 (triplet, 2H),

4.8 (broad hump, 2H), 6.30-7.30 multiplee, 3H), 8.10 (broad singlet, 2H),

9.1 (broad hump, 1H); ir (CHBr3 soln) cm-' 1195, 1650, 1695, 1715, 3295,

3385.

5(6)-(B-Hydroxyethyl)benzimidazole (29)

Crude B-(3-amino-4-formamidophenyl)ethyl format 28 (10.5 g, 0.050

mol) was dissolved in 100 ml of water and the solution was refluxed for

1 hour. The solution was then allowed to cool to room temperature slowly

and decolorizing charcoal was added. After filtering the charcoal, the

solution was concentrated to a volume of about 20 ml and neutralized with

sodium bicarbonate. The precipitated product was then filtered and re-

crystallized from water to give 3.70 g (46%) product: mp 138-140C, lit23

mp 140-142*C, nmr (dmso-dg) 6 2.75 (triplet, 2H), 3.60 (triplet, 2H),

6.80-7.40 multiplee, 3H), 8.00 (singlet, 1H); ir (CHBr3 soln) cm-1 800,

945, 1060, 1245, 1295, 1365, 1480, 3000 (broad).

5(6)-(B-Chloroethyl)benzimidazole Hydrochloride (30)

In small portions 5(6)-(B-hydroxyethyl)benzimidazole 29 (3.5 g,

0.022 mol) was added to 25 ml thionyl chloride with stirring. The mixture

was refluxed for two hours. The precipitate which formed during the reflux

period was filtered and washed with ether to give 4.5 g (95%) product:

mp 125-127*C, lit23 mp 126-128*C; nmr (dmso-d6) 6 3.25 (triplet, 2H),
3.95 (triplet, 2H), 7.50-8.00 multiplee, 3H), 9.70 (singlet, 1H); ir

(Nujol mull) cm-1 710, 1163, 1610, 2700 (broad).

Benzyl N-Methylbenzohydroxamate (33)

Dry sodium hydride (0.70 g, 22 mmol) and 8 ml dry THF were charged

into a 3-necked round bottomed flask equipped with magnetic stirrer,








condenser, dropping funnel and dry N2 inlet. A solution of benzyl benzo-

hydroxamate 32 (6.0 g, 26 mmol) in 30 ml dry THF was added over 30 minutes

with stirring at room temperature. When H2 evolution had subsided, methyl

iodide (2.0 ml, 4.7 g, 33 mmol) in 8 ml dry THF was added dropwise. The

resulting solution was heated at a gentle reflux for 1 one-half hours.

A small amount of methanol was added to decompose the excess NaH, and

the solvent was evaporated under reduced pressure. The resulting oily

solid was partitioned between CH2C12 and water. The layers were separated

and the aqueous layer was extracted again with CH2C12. The combined organ-

ic layers were dried (MgSO4) and filtered. Evaporation of the solvent gave

5.9 g (93%) of product as a clear yellow oil:13 nmr (CDC13) 6 3.33 (sing-

let, 3H); 4.66 (singlet, 2H); 6.93-7.80 multiplee, 10H); ir (neat) cm'l

650, 690, 750, 970, 1150, 1210, 1375 (broad), 1430 (broad), 1640 (broad),

3020 (broad).

Ethyl (N-Hydroxy)ethanimidate (38)

Ethyl ethanimidate hydrochloride (50.0 g, 0.405 mol) was added to

250 ml of 3.25 M K2C03 solution and was stirred at 0C for 10 minutes.

The resulting free base was quickly extracted with 3 x 75 ml ether. The

combined ethereal extracts were washed with 3 x 25 ml water. A solution

of hydroxylamine hydrochloride (35.5 g, 0.511 mol) in 125 ml water at 0C

was added to the ethereal extracts, and the mixture was shaken vigorously

for 10 minutes. The ether layer was separated and dried (MgS04).

Evaporation of the solvent gave an oil, from which 17.1 g (41.0%) product

was obtained by fractional distillation (85-88C, 50 mm Hg; lit27 bp

54.50C, 9 mm Hg): nmr (CDC13) 6 1.25 (triplet, 3H), 2.00 (singlet, 3H),

4.00 (quartet, 2H), 8.40 (broad singlet, 1H); ir (neat) cm-1 980, 1007,

1052, 1300, 1375, 1660, 3200-3500 (broad).







p-Methoxybenzyl Chloride (39)

Benzene (88 ml), p-methoxybenzyl alcohol (10.0 g, 0.0724 mol), and

0.20 ml pyridine were stirred together and 9.1 ml SOC12 slowly pipetted

into the solution. The reaction mixture was refluxed for two hours. Af-

ter evaporation of the solvent and excess SOC12, the residue was taken

up in 20 ml ether and washed with 2 x 20 ml H20. The ether layer was dried

(MgSO0) and evaporated to give an oil. Distillation (91-93C, 7 mm Hg;
lit28 bp 1200C, 20 mm Hg) gave 10.0 g (88.5%) product as a colorless oil:

nmr (CDCI3) 6 3.73 (singlet, 3H), 4.52 (singlet, 2H), 7.10 (quartet, 4H);

ir (neat) cm-1 660, 730, 830, 1030, 1175, 1245 (broad), 1300, 1510, 1610,

2840, 2960.

Ethyl N-(p-Methoxybenzyloxy)ethanimidate (40)

Sodium metal (3.8 g, 0.166 mol) was dissolved in 85. ml ethanol.

Ethyl (N-hydroxy)ethanimidate 38 (17.1 g, 0.166 mol) was added and the

resulting solution was stirred at room temperature for one-half hour;

p-methoxybenzyl chloride 39 (26.0 g, 0.166 mol) was added dropwise and the

reaction mixture was stirred overnight at room temperature. The ethanol

was evaporated and the residue was partitioned between 30 ml ether and

30 ml water. The layers were separated and the water layer was extracted

with 2 x 30 ml ether. The combined ethereal extracts were dried (MgS04)

and evaporated to give an oil. Fractional distillation (120-122OC; 6 mm

Hg; lit9" bp 140C, 10 mm Hg) gave 22.0 g (59.4%) product as a colorless

oil: nmr (CDC13) 6 1.23 (triplet, 3H), 1.93 (singlet, 3H), 3.77 (singlet,

3H), 4.00 (quartet, 2H), 7.13 (quartet, 4H); ir (neat) cm-' 823, 1030,

1243, 1300, 1375, 1510, 1613, 1640, 2900-3000 (broad).







0-(p-Methoxybenzyl)hydroxylamine Hydrochloride (41)

Ethyl N-(p-methoxybenzyloxy)ethanimidate (15.0 g, 0.067 mol) was

dissolved in 10. ml ether and water (1.21 ml, 0.0-7 mol) was added. The

mixture was cooled to 0C and 20 ml of ether saturated with HC1 gas was

added with stirring. The resulting precipitate was filtered and washed

with ether to give 9.60 g (75.4%) product as a white solid (mp>2000C,

lit29 mp>2000C. The product may be recrystallized from ethanol but was

generally used as obtained: nmr (dmso-dg) 6 3.80 (singlet, 3H), 5.03

(singlet, 2H), 7.27 (quartet, 4H).

p-Methoxybenzyl Benzohydroxamate (42)

A flask containing a mechanically stirred slurry of 0-(p-methoxy-

benzyl)hydroxylamine hydrochloride 41 (33.6 g, 0.177 mol) in 500 ml dry

THF was cooled to 0C and triethylamine (51.8 ml, 37.7 g, 0.372 mol) added

dropwise. After stirring 15 minutes, benzoyl chloride (20.6 ml, 24.9 g,

0.177 mol) in 25 ml THF was added dropwise. The reaction mixture was

stirred an additional 15 minutes at 0OC, then allowed to warm to room

temperature and was stirred one-half hour. The solvent was evaporated

and the residue was partitioned between 75 ml CH2C12 and 75 ml 0.25 M HC1.

The organic layer was separated and extracted with 3 x 50 ml 2 N NaOH.

These basic extracts were acidified with concentrated HC1 (to pH =2) and

extracted with 4 x 50 ml CH2C12. The organic layer was dried (MgS04)

and evaporated to give 39.0 g (85.7%) product as a light yellow oil:

nmr (CDC13) 6 3.70 (singlet, 3H), 4.87 (singlet, 2H), 6.80-7.70 (multi-

plet, 9H), 8.50 (broad hump, 1H); ir (CHBr3 soln) cm-1 820, 1030, 1250,

1305, 1512, 1645, 3250.







(p-Methoxybenzyl)-N-methylbenzohydroxamate (43)

Dry sodium hydride (0.16 g, 6.8 mmol) and 2.0 ml dry THF were charged

into a 3-necked round bottom flask equipped with magnetic stirrer, conden-

ser, dropping funnel, and dry N2 inlet. A solution of (p-methoxybenzyl)-

benzohydroxamate 42 (1.50 g, 5.8 mmol) in 8 ml dry THF was added to the

NaH slurry over one-half hour at room temperature with stirring. When H2

evolution ceased, methyl iodide (0.48 ml, 1.10 g, 7.8 mmol) in 5 ml dry

THF was added dropwise. The slightly turbid solution was refluxed for

two hours. A small amount of methanol was added to decompose the excess

NaH, and the solvent was evaporated under reduced pressure. The resulting

oily solid was partitioned between CH2C12 and water. The layers were

separated and the aqueous layer was extracted again with CH2C12. The com-

bined organic layers were dried (MgS04) and filtered. Evaporation of the

solvent gave 5.75 g (90.2%) product as a colorless oil: nmr (CDC13) 6

3.30 (singlet, 3H), 3.70 (singlet, 3H), 4.75 (singlet, 2H), 6.25-7.35

multiplee, 9H); ir (CHBr3 soln) cm-' 690, 750, 970, 1160, 1375, 1630,

3030.

N-Methyl-0-(p-Methoxybenzyl)hydroxylamine Hydrochloride (44)

In 17.7 ml 10% w/v NaOH, (p-methoxybenzyl)-N-methylbenzohydroxamate

43 (10.0 g, 37. mmol) was dissolved in methanol. After stirring for 15

minutes, 10. ml methanol was added in order to break up the thick pre-

cipitate which had formed. After stirring an additional four hours, 25.

ml water was added and the methanol was evaporated. The resulting mixture

was extracted with 2 x 20 ml ether. The ethereal extract was dried

(MgS04) and cooled to 0OC. Ether (20 ml) saturated with HC1 gas at 0C
was added. The resulting solid was filtered. Recrystallization (ethanol)

gave 6.0 g (80.0%) product as white crystals: mp 123-125; nmr (dmso-d6)
6







6 2.90 (singlet, 3H), 3.83 (singlet, 3H), 5.20 (singlet, 2H), 7.30 (quar-

tet, 4H).

Anal. Calcd. for C6HI4N 02C1: C, 53.10; H, 6.88; N, 6.88

Found: C, 52.96; H, 6.93; N, 6.83.

PS-DVB-VBVIm (46)

Styrene (0.2779 g, 2.67 mmol), p-vinylbenzoyl-4(5)-vinylimidazole

(45.2 mg, 0.201 mmol), divinylbenzene (0.4931 g, 3.76 mmol) and AIBN

(11.0 mg, 0.067 mmol) were dissolved in 0.91 ml CH3CN/toluene (50:50 v/v)

and the solution was degassed. The polymerization was carried out under

a dry N2 atmosphere at 50C for five days. The resulting polymer was

ground with a mortar and pestle and sieved to give uniformly sized par-

ticles of between 177-420 um in diameter: ir (KBr pellet) cm-1 1700, 1601.

Anal. Calcd. for C, 90.95; H, 7.74; N, 0.91.

Found: C, 90.65; H, 7.80; N, 0.85.

PS-DVB-VIm-VBIm (47)

Styrene (0.2569 g, 2.47 mmol), 5(5)-vinylimidazole (19.0 mg, 0.201

mmol), p-vinylbenzoylimidazole (40.0 mg, 0.201 mmol), divinylbenzene

(0.4931 g, 3.78 mmol), and AIBN (11.0 mg, 0.067 mmol) were dissolved in

0.90 ml CH3CN/toluene (50:50 v/v) and the solution was degassed. The

polymerization was carried out under a dry N2 atmosphere at 50C for five

days. The resulting polymer was ground with a mortar and pestle and

sieved to give uniformly sized particles of between 177-420 im in diameter:

ir (KBr pellet) cm-' 1700, 1601.

Anal. calcd. for C, 90.27; N, 7.71; H, 1.60.

Found: C, 89.98; N, 7.83; H, 1.53.







Mono-PS-DVB-VIm (48)

Styrene (0.2779 g, 2.67 mmol), 4(5)-vinylimidazole (19.0 mg, 0.201

mmol), divinylbenzene (0.4931 g, 3.78 mmol) and AIBN (11.0 mg, 0.067 mmol)

were dissolved in 0.88 ml CH3CN/toluene (50:50 v/v) and the solution was

degassed. The polymerization was carried out under a dry N2 atmosphere

at 50C for five days. The resulting polymer was ground with a mortar

and pestle and sieved to give uniformly sized particles of between 177-

420 pm in diameter: ir (KBr pellet) cm'' 1601.

Anal. Calcd. for C, 91,20; H, 7.95; N, 0.94.

Found: C, 90.97; H, 7.98; N, 0.92.

PS-DVB-VBVBenz (49)

Styrene (0.3534 g, 3.40 mmol), p-vinylbenzoyl-5(6)-vinylbenzimidazole

(69.5 mg, 0.25 mmol), divinylbenzene (0.6204 g, 4.75 mmol), and AIBN

(13.9 mg, 0.085 mmol) were dissolved in 1.16 ml CH3CN/toluene (50:50 v/v)

and the solution was degassed. The polymerization was carried out under

a dry N2 atmosphere at 50C for five days. The resulting polymer was

ground with a mortar and pestle and sieved to give uniformly sized par-

ticles of between 177-420 pm in diameter: ir (Nujol mull) cm-1 1700,

1601.

Anal. Calcd. for C, 91.02; H, 7.77; N, 0.90.

Found: C, 90.93; H, 7.88; N, 0.69.

PS-DVB-VBenz-VBBenz (50)

Styrene (0.3552 g, 3.41 mmol), 5(6)-vinylbenzimidazole (39.5 mg,

0.274 mmol), p-vinylbenzoylbenzimidazole (68.1 mg, 27.4 mmol), divinylben-

zene (0.6742 g, 5.16 mmol), and AIBN (15.0 mg, 0.091 mmol) were dissolved

in 1.27 ml CH3CN/toluene (50:50) and the solution was degassed. The poly-

merization was carried out under a dry N2 atmosphere at 500C for five days.








The resulting polymer was ground in a mortar and pestle and sieved to give

uniformly sized particles of between 177-420 um in diameter: ir (Nujol

mull) cm-1 1601, 1700.

Anal. Calcd. for C, 90.62; H, 7.64; N, 1.34.

Found: C, 90.35; H, 7.79; N, 1.27.

Mono-PS-DVB-VBenz (51)

Styrene (0.3500 g, 3.36 mmol), 5(6)-vinylbenzimidazole (36.5 mg,

0.25 mmol), divinylbenzene (0.6236 g, 4.77 mmol), and AIBN (13.9 mg,

0.085 mmol) were dissolved in 1.10 ml CH3CN/toluene (50:50) and the solu-

tion was degassed. The polymerization was carried out under a dry N2 at-

mosphere at 50C for five days. The resulting polymer was ground in a

mortar and pestle and sieved to give uniformly sized particles of between

177-420 pm in diameter: ir (Nujol mull) cm-' 1601.

Anal. Calcd. for C, 91.28; H, 7.79; N, 0.94.

Found: C, 91.06; H, 7.84; N, 1.00

PS-DVB-VBBenz (52)

Styrene (0.3496 g, 3.36 mmol), p-vinylbenzoylbenzimidazole (63.0

mg, 0.25 mmol), divinylbenzene (0.6280 g, 4.81 mmol) and AIBN (13.9

mg, 0.085 mmol) were dissolved in 1.16 ml CH3CN/toluene (50:50 v/v) and

the solution was degassed. The polymerization was carried out under a

dry N2 atmosphere at 500C for five days. The resulting polymer was

ground in a mortar and pestle and sieved to give uniformly sized parti-

cles of between 177-420 um in diameter: ir (Nujol mull) cm'' 1700,1601.

Anal. Calcd. for C, 91.01; H, 7.70; N, 0.90.

Found: C, 90.95; H, 7.82; N, 0.73.







Polymers 54-58. General Method of Cleavage by Anion 53

Under an argon atmosphere, N-methyl-0-(p-methoxybenzyl)hydroxylamine

hydrochloride (0.2000 g, 0.9826 mmol) in dry THF (1.0 ml) was treated with

n-butyllithium (1.21 ml of a 1.3 M solution in hexane) at -780C. The re-

sulting solution was filtered under argon pressure onto 0.2000 g of the

appropriate polymer and allowed to warm to room temperature. After 12

hours water was added and the polymer was filtered from the solution. The

polymer was then shaken for 36 hours in 50:50 v/v dmso/H20, filtered,

washed with CHCN, and dried under vacuum. All polymers showed a shift in

carbonyl frequency to 1632 cm' .

Anal.

ordered PS DVB-IM-MHAOCH2Ar 54

calc'd: C, 89.91; H, 7.75; N, 1.20

found: C, 90.14; H, 7.82; N, 1.12

random PS-DVB-Im-MHAOCH2Ar 55

calc'd: C, 89.94; H, 7.76; N, 1.23

found: C, 89.85; H, 7.82; N, 1.18

ordered PS-DVB-Benz-MHAOCH2Ar 56

calc'd: C, 89.98; H, 7.69; N, 1.19

found: C, 89.72; H, 7.78; N, 1.04

random PS-DVB-Benz-MHAOCH2Ar 57

calc'd: C, 89.95; H, 7.70; N, 1.19

found: C, 89.68; H, 7.69; N, 1.04

mono- PS-DVB-MHAOCH2Ar 58

calc'd: C, 90.51; H, 7.76; N, 0.51

found: C, 90.27; H, 7.80; N, 0.47







Polymers 59-63. General Method of Dealkylation of Polymer-Bound
Hydroxamate Ester

The appropriate polymer was placed in a Kel-F reaction vessel and

anhydrous hydrogen fluoride was vacuum transferred onto the polymer.

The reaction mixture was then warmed to room temperature. After 24

hours the hydrogen fluoride was then removed under reduced pressure.

The resulting polymers were then washed with CH3CN and vacuum dried.

Anal.

ordered PS DVB Im DHA 59
calc'd: C, 90.20; H, 7.77; N, 1.23
found: C, 90.28; H, 7.85; N, 1.15

random PS DVB Im MHA 60
calc'd: C, 90.14; H, 7.78; N, 1.26
found: C, 90.05; H, 7.80; N, 1.20

ordered PS DVB Benz MHA 61
calc'd: C, 90.07; H, 7.70; N, 1.20
found: C, 89.87; H, 7.79; N, 1.08

random PS DVB Benz MHA 62
calc'd: C, 90.05; H, 7.70; N, 1.23
found: C, 89.93; H, 7.67; N, 1.10

mono PS DVB Benz MHA 63
calc'd: C, 90.61, H, 7.77; N, 0.57
found: C, 90.54; H, 7.68; N, 0.53

Kinetics

General Kinetic Method

Kinetics were performed using polymer fractions which passed through

a No. 40 U.S. Standard Sieve but were retained by a No. 80 U.S. Standard

Sieve. The amount of polymer (6 mg for pseudo-first-order runs, 1.25 mg

for burst runs) was weighed on an electrobalance and placed directly in

a cuvett. The appropriate buffer (3.00 ml) was pipetted into the cuvett








and the polymer was allowed to regain the solvent for one-half hour.

The ester solution was added to the cuvet: using a microliter syringe.

The cuvet was capped, shaken, and the time was recorded. The cuvet

holder was thermostatted at 25C. The cuvet was shaken at five minute

intervals and absorbance readings were taken every one-half hour.

The formation of p-nitrophenolate or 2,4-dinitrophenolate was observed

at 400 nm. Infinity absorbances were obtained by periodically measur-

ing the absorbances until two consecutive measurements were the same.

The observed rate constants were obtained by a least squares program.

Correlation coefficients were always 0.999 or better. All reactions

were followed through at least two half-lives. All kinetic runs were

made at least twice. For pseudo first order runs the concentration of

ester substrate was 5.00 x 1O-SM and the catalyst was used in 20-fold

excess. Burst kinetic runs were performed with the substrate in 15-20

fold excess of the catalyst.


Sample Site Access Calculation

The steady state portion of the burst curve was followed until ten

points (taken at fifteen minute intervals) gave a straight line. A

Texas Instruments Programmable 58 linear regression program was used to

determine the line through the points. For ordered PS-DVB Benz-MHA 61

the line was

y = 2.03 x 10-3 x + 0.742

Using Beer's Law

0.742 (1.17 x 104) [active sites]

6.35 x 10-5 = [active sites]
'Since the active sites are mounted on an insoluble support, the term







"concentration" of active sites has no real meaning. Therefore,

this number must be multiplied by the volume of solution to give

the number of moles of active sites.


(6.35 x 10 active site) 3.00 x 10-3 = 1.90 x 10-7 mol active sites


In this experiment, 1.1820 mg of catalyst was used containing

(theoretically) 5.72 x 10-7 moles of functional groups. Access is

therefore


1.90 x 10-7 mol active site .
100% = 33.2% access
5.72 x 10-7 mol sites total


Sample Calculation of Polymer Elemental Composition

The elemental composition of PS-DVB-VIm (47) was determined as

follows. Contributions of each monomer to the total elemental

composition were calculated.

N-(p-Vinylbenzoyl)imidazole 17

0.0040 g gives C 0.0291 g
C12HIoN2 H 0.0020 g
N 0.0056 g

4(5)-Vinylimidazole

0.0190 g gives C 0.0121 g
C5H6N, H 0.0012 g
N 0.0056 g

Styrene

0.2569 g gives C 0.2371 g
CBHB H 0.0198 g

80:20 Divinylbenzene/ethyl styrene

0.4931 g gives C 0.4538 g
CIoH1io4 H 0.0393







AIBN (after loss of N2)


0.0091 g
CH1 N,


gives C 0.0064 g
H 0.0008 g
N 0.0019 g


Total wt. of polymer = 0.8181 g

Therefore:


% C = 100% x


(0.0291g + 0.0121g


+ 0.2371g + 0.4538g + 0.0064g)
0.8181g


= 90.27


% H = 100% x


(0.0020g + 0.0012g + 0.0198g + 0.0393g + 0.0008g)
0.8181g


= 7.71


% N = 100% x


(0.0056g +


0.0056g + 0.0019g)
0.8181g


= 1.60













REFERENCES


1. G. Manecke and W. Storck, Ang. Chem. (Eng. Ed.), 17 (9), 657 (1978).

2. D.C. Sherrington, Br. Polym. J., 12, 70 (1980).

3. M.I. Page, Macromol. Chem. (London), 397 (1980).

4. C.G. Overberger and J.C. Salamone, Acc. Chem. Res., 2, 217 (1969).

5. L. Michaelis and M.L. Menten, Biochem. Z., 49, 333 (1913).

6. K.J. Laidler and P.S. Bunting in "The Chemical Kinetics of Enzyme
Action," 2nd ed. (Clendon Press, Oxford, 1973), Chap. 1.

7. J.D. Roberts and W.W. Bachovchin, J. Amer. Chem. Soc., 100, 8041
(1978).

8. W.P. Jencks, "Catalysis in Chemistry and Enzymology" (McGraw-Hill,
1969), p. 68.

9. C.G. Overberger, T. St. Pierre, N. Voichmeier, J. Lee, and S. Yaro-
slavsky, J. Amer. Chem. Soc., 87, 296 (1965).

10. C.S. Lege and J.A. Deyrup, Macromolecules, 14, 1629 (1981).

11. C.S. Lege and J.A. Deyrup, Macromolecules, 14, 1634 (1981).

12. C.G. Overberger, J.C. Salamone, and S. Yaroslavsky, J. Amer. Chem.
Soc., 89, 6231 (1967).

13. T. Kunitake and Y. Okahata, J. Amer. Chem. Soc., 98, 7793 (1976).

14. G. Wuiff and I. Schulze, Ang. Chem. (Eng. Ed.), 17, 537 (1978).

15. G. Wiilff, W. Vesper, R. Grobe-Einsler, and A. Sarhan, Makromol.
Chem., 178, 2799 (1977).

16. E.J. Langenmayr, Ph.D. Dissertation (University of Florida,
Gainesville, Florida, 1980).

17. J.R. Millar, D.G. Smith, W.E. Marr, and T.R.E. Kressman, J. Chem.,
Soc., 218 (1963).

18. A.V. Del Guercio, M.S. Thesis (University of Florida, Gainesville,
Florida, 1983).







19. S.L. Regen, Ang. Chem. (Eng. Ed.), 18, 421 (1979).

20. M. Bernard and W.T. Ford, J. Org. Chem., 48, 327 (1983).

21. H.A. Staab, Ang. Chem. (Eng. Ed.), 1, 351 (1962).

22. C.G. Overberger and N. Vorchmeier, J. Amer. Chem. Soc., 85, 951
(1963).

23. C.G. Overberger, B. Kosters, and T. St. Pierre, J. Poly. Sci. Part
A-i, 5, 1987 (1967).

24. J. Leebrick and H.E. Ramsden, J. Org. Chem., 23, 935 (1958).

25. Y. Iwakura, Bull. Chem. Soc. Japan, 41, 186 (1968).

26. M.E. Jung and M.A. Lyster, J. Amer. Chem. Soc., 99, 968 (1977).

27. W.N. Marmer and G. Maerker, J. Org. Chem., 37, 3520 (1972).

28. M. Simonette and G. Favini, J. Chem. Soc., 1840 (1954).

29. Y.V. Markova, N.G. Ostroumova, and M.N. Shchukina, Zh. Org. Khim.,
3, 1207 (1967).

30. J.P. Tam, W.F. Heath, and R.B. Merrifield, J. Amer. Chem. Soc.,
105, 6442 (1983).

31. P.A.S. Smith, "Open Chain Nitrogen Compounds" 1st Edition (W.A.
Benjamin, New York, 1965), Chapter 8.

32. J. Lenard and A.B. Robinson, J. Amer. Chem. Soc., 89, 181 (1967).

33. S.J. Thomas and G. Webb, "Heterogeneous Catalysis" 1st Edition,
(Wiley, New York, 1968).

34. F. Helfferich, "Ion Exchange" (McGraw-Hill, New York, 1972)
pages 84-94.

35. D.S. Hartley and B.A. Kilbey, Biochem. J., 56, 288 (1954).

36. H. Gutfreund and J.M. Sturtevant, Biochem. J., 63, 656 (1956).



















APPENDIX














PS-OVB-VBVIm 46



lllll II IIIlilil-i!|l::^|ll i:!;||^ I I I III- i I
." 1 T. :.L.-.:^
_:f --f t -1 i I I f l





--t










O -404
-- -'t-







T-



: 7-- d








-- t -






















2000 1800 1600 1400 W I
!---- i;


ABSCISSA










ordered-PS-AB- In-:.HAjCH Ar 54


1-4-4-


K~t


iHI
L4-+
I -, -


I if
T i I ; 7




-- -- -- JT








- _7 1


1` --
-Tr# I t


4 40j--;
4- Hi
F 1 -14 t -l -i T -


T I 17

if 7




4- 4 -
-T~ Lr: -,-- 20
T_44+


S1 -1


-7: TVI*
.74 i.


I-


-. 1


-fi


-
*-'1


1-

; 11


a-') T-


^


~.,~.


1 I
-r

+I


ii71
-t~'fl












ordered PS-DVB-Iri-InHA 59








-ii
Ti il














0-r 4 1,
TE .... ; :E:.::I:::::II





















2000 1800 1600 1400 WAVI
VBr ,-e.I ABSCISSA .

nION. O'l itAt P I-PV.J -3- lEP. SCAN EXPANSIONN
HIGH UMIT SUPPRESSION-
I l i l t I





4--






+ 0010 6010 WV
r~r ~~k~c+ sjaj7
\rlo mduprPs-Rb -u--C11~ Rf. s~ll (P;SJ4
T-+UM~~lLSO













PS-LVB-VBIm 47


4tI


-4++4


J 1...
-t- +-,
tr':


4i~i-


:4lf 'Z


I;3 m 4 7=7
:j:T ~ di:^N*4-^4%^i ^ ^-r1 i; ."4


* 2000 1800 1600 1400 WAV
--I ABSCISSA


HH!,+ HH +H +H !H!


--I--,-I
4-t
7-f7


i


. . .


I+H ++ HffjifT m i nffim444444 JIT


F- F -


Iffl^H-i


I I I '


I '


1-I ..
L
: : ij


LE Il


n


L1L=


dMtI444-




77









rendon PS-DMb-In-, ;1iAJCH2 Ar


MlrOIMCtDC Afl 7.f


V I = ii l........... ...... ..
J

1 :* ;?f- iiI ii ^ ^

.. 1 I Z t ,' -- ----

2--














S .:










:-I-- .-.- ---7i ,
---_
-- -- -- -4 -$iL
































-_---__-- ABSCISSA
S. SCN EXPANSION___________ AN T









___________________ IGH MIT SUPPRESSION --
-- "O LTD1__ O- LT _. S POGAM -
-- -4-
.. ..- ....- .:- -;#- .;,,









I If

4r. -TA XPNI SCAN TU t
"IrDIMILC-e-c A












































LOW LIMIT -TIME DRIVE M PROGAM -


o00


*ln
















radon PS-ujVB-Iri-."HP 60
S.D MttROM~FlFR


f.*06


41 i 41 j 4 -1



80'' ,
H +H-Ii "


_f"A 7- -4:-:"- -




rt .. j _;Z



i -- i -. .-I-, T-






.......is- ; i

I~ ]71







1 `1 7
5 n MICR METERS
..,.. __ a c
1-1-.-- A 7.I- -






























2000 100 160 140 WAVE


B.C















PS-DVB-VBenz-VBBenz 50


-HH-i fl----]FF-HdHHdF- H ]


r.n on


u.Il^ AiiTi ''I | i
4 : ^ ^ A- ,-.--.. ---., ..L
I IV 0 1 Il, t III o .1 1 1 1i




t-i




1-2--
7. -. 77











1 6 00'l-. 4 01R- '



















----------- ABSCISSA

(ATuO_ SEP. SCAN EXPANSION___________ SCAN TIML_
I------------------------------ kWH UMIT ..... SUPPtESiION. RESPONSE_______
O _t T OIA_











T T -r -r T -T -- --F I--_l "-
-4-1


d YlrnYf~~r ~d tn

















random PS-OVB-Benz h:HAOCH2Ar 57

50 MICROMETERS 60
*P^^^P^^^II^I~l^^Lij-_i


4 4I 4 I I I I IlI I I 44J-'l -I l44l


. I I


a A


II


S8;(


,- ,- 4 ,-


'T i+ +--7

-Hi+:



r IC



F 44 r H, +-t
A


T- 17-r

4- f




I- Lj

I-77

-2-

-7 1
7 14--L

17
rt i I
+ 7TI,. --

I Tf- -'-T


i ++ H- -- -, L


2000


1800


1600


4+! ill I


:y!ff~I~t~SSBW


1400 WAVE

















random PS-DVB-Benz-h'HA 62
c.n UnTrPnMAFTF


70


T1.7
III fill~ i
=T


-, L'




0-
J, 1 :1 1

4 1 14- 7 7-t:~
i+i
4 i j -
:17 4-i-AA7~7:tt--~f


2.14 44-


T= 6Q-~tt~tt -r
TS-++


ltfliCtC--:' i -Ti t 1.i -T 1-

-I --- FT-C


c- I----I- I 4- -40I


i--7=


717






---4-

L lI



4 --
i :-1I ,A































':C__144


1800 1600 1400 V.


2000


66






















PS-DVB-VBVBenz 49
J3 L jAvI _LL h i r AER


F 4H



4-114: -

:c
Tl -;7 7------
-7

T-7-


If -'4--





I i
--4




f7- I



-T- -4- : 4 -







7 1t







i-1 -7-
4-i


-7



141
jw I MI o irrr l








































20001800160 140 WA


~111













I.~ ii


- I i;ii 1


II


'-''
1_


77'.
1 i-- -- -z. -- --
~LJ


1 .I -- -
4- 1 -4








+ -,- --- ;!.; .- -- -- .. .
-! -4--.-. i -;. : "








I 9G LMT..SPRESIN
4-"W --+i- -TE

4- 4 .
- A 4- 7 1 71- .-. I-



4---
I -~h -t

:41
-$ JL $1' -.- -- wt-z:
LIL



i +-.-- I -4- -77



2000 1800 1600 1400 WAVi
ABSCISSA
__ ___ REP. SCAN -EXPANSION_
______________________________ HIGH LIMIT SUPPRESSION________
LIMt AT







LOW IMIT TIE IDIVI


_ LA


-'--8
,,.
r'r^.8


I I


I


~ii_-l I



- -


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BIOGRAPHICAL SKETCH


John Carter Leighton was born on October 26, 1957 in Durham,

North Carolina. Doctors were called during the halftime festivities

of the Duke N.C. State football game to deliver him. The outcome

of the game is still unknown.

After an uneventful childhood, the author spent three injury-filled

years trying to pose as a high-school basketball star. He then gave

up athletics in disgust, and decided to go to the University of

Florida. Four years later, he had a Bachelor's degree in Chemistry

but no real motivation to get a job. Therefore, he decided to get a

Ph.D. in Chemistry and hope the motivation came later.

That motivation came in the summer of 1981, when he met

Jeannette Ann Murray. After a whirlwind romance they were married on

December 10, 1983 just in time to move to Basking Ridge, New Jersey

and go to work at the National Starch and Chemical Corporation.







I certify that I have read this study and that in my opinion it
conforms to acceptable standards of scholarly presentation and is
fully adequate, in scope and quality, as a dissertation for the
degree of Doctor of Philosophy.



(/ames A. Deyru; Chairman
Professor of Chemistry


I certify that I have read this study and that in my opinion it
conforms to acceptable standards of scholarly presentation and is
fully adequate, in scope and quality, as a dissertation for the
degree of Doctor of Philosophy.



/terhard M. Schmid
Associate Professor of Chemistry


I certify that I have read this study and that in my opinion it
conforms to acceptable standards of scholarly presentation and is
fully adequate, in scope and quality, as a dissertation for the
degree of Doctor of Philosophy.



J njG. Dorsey
As stant Professor of Chem y


I certify that I have read this study and that in my opinion it
conforms to acceptable standards of scholarly presentation and is
fully adequate, in scope and quality, as a dissertation for the
degree of Doctor of Philosophy.


Ben M. Dunn
Associate Professor of Biochemistry


I certify that I have read this study and that in my opinion it
conforms to acceptable standards of scholarly presentation and is
fully adequate, in scope and quality, as a dissertation for the
degree of Doctor of Philosophy.


Prhn A. Zoltewiczs
Professor of Chemistry











This dissertation was submitted to the Graduate Faculty of the
Department of Chemistry in the College of Liberal Arts and Sciences
and to the Graduate Council and was accepted as partial fulfillment
of the requirements for the degree of Doctor of Philosophy.




Dean for Graduate Studies and Research