Title: Nuclear magnetic resonance study of the trifluorovinyl group
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 Material Information
Title: Nuclear magnetic resonance study of the trifluorovinyl group
Physical Description: vi, 58 l. : illus. ; 28 cm.
Language: English
Creator: Moreland, Charles Glen, 1936-
Publication Date: 1964
Copyright Date: 1964
 Subjects
Subject: Nuclear magnetic resonance   ( lcsh )
Organofluorine compounds   ( lcsh )
Magnetic Resonance Spectroscopy   ( mesh )
Chemistry thesis Ph. D
Dissertations, Academic -- Chemistry -- UF
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Thesis: Thesis - University of Florida.
Bibliography: Bibliography: l. 54-57.
Additional Physical Form: Also available on World Wide Web
General Note: Manuscript copy.
General Note: Vita.
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Bibliographic ID: UF00097937
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: alephbibnum - 000423879
oclc - 11022254
notis - ACH2284

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NUCLEAR MAGNETIC RESONANCE STUDY

OF THE TRIFLUOROVINYL GROUP














By
CHARLES G. MORELAND


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
August, 1964












ACKNOWLEDGMENTS


The author wishes to express his sincere appreciation

to Dr. W. S. Brey, Jr., Chairman of the author's Supervisory

Committee, for his constant guidance and help. His ideas

and many helpful suggestions have been vital factors in the

success of this work.

The completion of this work is due in no small part

to the understanding and encouragement shown by the author's

wife, Nancy. To her no written acknowledgment is adequate.

To Mr. Ward Oliver and Miss Geraldine Westmoreland,

the author is indebted for the preparation of many of the

compounds studied in this investigation.

The author also wishes to thank Mrs. Thyra Johnston

who typed this dissertation and was very helpful in the

proofreading.














TABLE OF CONTENTS


ACKNOWLEDGMENTS . . . . . .

LIST OF TABLES. . . . . .

LIST OF FIGURES . . . . .

HISTORICAL BACKGROUND . . . . .

INTRODUCTION. . . . . . .

EXPERIMENTAL AND EXPERIMENTAL RESULTS .

Experimental . . . . . .

Experimental Results . . . .

DISCUSSION. . . . . . . .

Effect of Conjugation on Jab and the
Shifts of Fa . . . . .


* *

* *


. . .

. . .

. . .

Chemical
. . .


Page

. ii

. iv



S. 1
. 1


. 15

. 15


. 16

. 42


. 42


Dependence of the Chemical Shifts


of F and J


on the Electronegativity of the Substituent
Atoms . . . . . . . . . .

Temperature Dependence of the Coupling Constants
Jab and Jax ... . . . .

SUMMARY . . . . . . . . . . .

LIST OF REFERENCES . . . . . . .

BIOGRAPHICAL SKETCH . . . . . . . .










iii


. 0 .












LIST OF TABLES


Table Page

1. Chemical Shifts and Coupling Constants Within
the Trifluorovinyl Group at 32C for Compounds
in Groups I and II. . . . . . . . 17

2. Chemical Shifts and Coupling Constants Within
the Trifluorovinyl Group at 32C for Compounds
in Group III . . . . . . . .. 18

3. Correlation of Jax and the Chemical Shifts of
F With the Electronegativity of the
Substituent Atoms . . . .... . . 21

4. The Temperature Dependence of Jab Observed in
Some Trifluorovinyl Compounds of Group I. . 24

5. The Temperature Dependence of Jab Observed in
Some Trifluorovinyl Compounds of Group II . 25

6. The Temperature Dependence of Jab Observed in
Some Trifluorovinyl Compounds of Group III. . 26

7. The Temperature Dependence of Jax Observed in
Some Trifluorovinyl Compounds of Group I. . 27

8. The Temperature Dependence of Jax Observed in
Some Trifluorovinyl Compounds of Group II . 28

9. The Temperature Dependence of Jax Observed in
Some Trifluorovinyl Compounds of Group III. . 29

10. The Temperature Dependence of Jbx Observed in
Some Trifluorovinyl Compounds of Group I. .. 36

11. The Temperature Dependence of Jbx Observed in
Some Trifluorovinyl Compounds of Group II . 57

12. The Temperature Dependence of Jbx Observed in
Some Trifluorovinyl Compounds of Group III. . 8
iv












LIST OF FIGURES


Figure Page

1. The correlation between Jab and the chemical
shifts of F observed in some of the
a
trifluorovinyl compounds . . . . . 20

2. The correlation between the chemical shifts of
F and the electronegativity of the
substituent atoms observed in some of the
trifluorovinyl compounds . . . . . 22

3. The correlation between Jax and the
electronegativity of the substituent atoms
observed in some of the trifluorovinyl
compounds . ...... .. . . 23

4. The temperature dependence of Jab observed in
some trifluorovinyl compounds of group I . 30

5. The temperature dependence of Jab observed in
some trifluorovinyl compounds of group II. . 31

6. The temperature dependence of Jab observed in
some trifluorovinyl compounds of group III .. 32

7. The temperature dependence of Jax observed in
some trifluorovinyl compounds of group I 3

8. The temperature dependence of Jx observed in
some trifluorovinyl compounds of group II. . 34

9. The temperature dependence of Jax observed in
some trifluorovinyl compounds of group III . 35

10. The temperature dependence of Jbx observed in
some trifluorovinyl compounds of group I . 39











Figure Page

11. The temperature dependence of Jbx observed in
some trifluorovinyl compounds of group II. .. 40

12. The temperature dependence of Jbx observed in
some trifluorovinyl compounds of group III . 41













HISTORICAL BACKGROUND


Since about 1950, a great deal of work has been

undertaken in order to explain the nature of F19 chemical

shifts and F19 F19 coupling constants. Although the

theoretical work has been limited and the experimental

results ambiguous at times, some advancements have been

made.

The chemical shift is caused by a magnetic shielding

of the nucleus due to the electron distribution about the

nucleus of interest. It consists of two terms: 1) Lamb's

(1) diamagnetic correction related directly to the electron

density at the nucleus, and 2) a paramagnetic term arising

from lack of spherical symmetry of the potential of the

electrons in the vicinity of the nucleus. Saika and

Slichter (2) devised a procedure for calculating the second-

order paramagnetic terms and were able to calculate the

shift between HF and F2. According to their theory,

variations in the local paramagnetic circulations of the

fluorine atom are the dominant cause of chemical shifts in

fluorine compounds. This paramagnetic contribution, which

represents a shift toward low field, is greatest in co-

valently bonded fluorine and is zero in the spherically

symmetric F ion. Based on this theory, the magnitude of








2

the paramagnetic contribution may thus be expected to depend

on the amount of ionic character in the chemical bond.

A series of binary covalent compounds was examined by

Gutowsky and Hoffman (3,4) in an attempt to determine the

effect of the electronic structure associated with bond

formation and of the electronic configuration of the other

atoms in the molecule. The results showed a decrease of

the nuclear magnetic shielding of the Fl9 nucleus with

increased electronegativity of the adjacent atom. This

implies that the more tightly electrons are held by the

atom bound to fluorine, the less effective the electrons

are in magnetically shielding the fluorine nucleus.

Fluorine magnetic resonance shifts have been measured

in the halomethanes (5). In the series CFH CF2H2, CF3

and CF4 there is a progressive displacement of the fluorine

chemical shifts to lower fields. Thus the effective group

electronegativity influencing the fluorine in each compound

may be expected to increase in the order -CH3 < -CH2F

< -CHF2 < -CF3. This, of course, is further support of the

general correlation of fluorine chemical shifts with electro-

negativity of the atom or group of atoms to which the fluorine

is bonded. One would expect a similar trend of the fluorine

shifts in the series CFC13, CF2C12, CF C1 and CF4. How-

ever, the observed chemical shifts are in the opposite

direction. Gutowsky (5) has proposed that, because of the











greater tendency of fluorine to form partial double bonds

as compared with chlorine, the F atom should be less

shielded as the number of chlorine atoms goes from zero to

three.

Fluorine chemical shifts for a number of fluorocarbons

and fluorocarbon derivatives have also been measured (6,7).

Two important trends found are: l).the progressive dis-

placement of F resonance to lower field in series CF, CF2

and CF3 and 2) the shift to lower field of the CF2 group

fluorine resonance as the electronegativity of the directly

attached substituent decreases. The first trend suggests

that the amount of charge which fluorine is able to draw

from a carbon decreases as the number of competing fluorines

bonded to carbon increase. From his measurements of several

perfluoroalkyl halides, Tiers (7) has postulated a "re-

pulsive unshielding" effect to account for the second trend.

The bulkiness of groups such as CC13 and I was considered to

give rise to steric interactions which compensate for the

lesser electronegativity in withdrawing electrons from a

neighboring CF2 group. Smith and Smith (8) have studied the

fluorine shifts of some chlorofluorocarbons and have also

observed the shift to lower fields of the fluorine resonance

as the total electronegativity of the atoms associated with

the nearest carbon atom decreases. A covalent bond or

double-bond mechanism was given by them as an explanation

of the observed change in the chemical shift values.










Investigations by Gutowsky, McCall, McGarvey and

Meyer (9) on the substituent effects in some fluorobenzene

derivatives led to an apparent direct relation between the

Hammett substituent constant and the nuclear shielding for

the fluorine nucleus attached to the benzene ring.

The theory of indirect nuclear spin-spin inter-

actions is based upon the complete Hamiltonian for the

electron nuclear interactions as was first outlined by

Ramsey and Purcell (10), and later developed in more detail

by Ramsey (11). There are three principal terms in the

Hamiltonian which contribute to spin-spin coupling. They

are an orbital term, a dipole-dipole term, and a Fermi term.

These three terms represent the interaction of the nuclear

magnetic moments with the electron orbital motion and with

the electron spin density at a distance from, and at, the

nucleus (12).

Physically, spin-spin coupling between nuclei arises

because of the magnetic interaction of each nucleus with

the spin or orbital angular momentum of a "local" electron,

together with the coupling of electron spins and/or orbital

angular moment with each other. In short, the nuclear

interactions proceed via the electronic structure of the

molecule.

The problem of the theoretical calculation of coupling

constants between protons has been considered by several









5

authors (13,14,15). It has been demonstrated that for the

coupling between protons only the Fermi contact term

contributes appreciably, and the magnetic dipolar and

electron-orbital interaction may be neglected. It is now

generally believed that proton-proton spin coupling proceeds

through the electronic structure in the intervening bonds

(14). This "through-bond" mechanism is in line with the

common observation that the magnitude of the coupling

constants decreases with increasing number of bonds sepa-

rating the nuclei.

On the other hand, not much progress has been made

in the theoretical prediction of fluorine-fluorine coupling

constants, although a considerable number of such coupling

constants have been determined experimentally. The most

complete treatment of this problem is that of McConnell

(16) who applied molecular orbital theory to the evaluation

of the coupling in C2F4, and demonstrated that reasonable

values for coupling constants could be obtained by

considering contributions from magnetic dipolar and electron-

orbital terms. Karplus (17), on the other hand, has

suggested that electron-orbital and dipolar electron-spin

terms often may not be very important. However, even though

Karplus, McConnell and others may disagree on the exact

mechanism involved in fluorine-fluorine coupling, they do

agree that the problem of fluorine-fluorine coupling is










certainly more complicated than in the case of coupling

between protons. This prediction was experimentally sub-

stantiated in 1956, when Saika and Gutowsky (18) reported

a near zero coupling constant between the fluorine atoms

on adjacent carbon atoms in the molecule CF3CF2N(CF )2.

This was particularly surprising, since the other two

constants are 16 cycles per sec (cps) and 6 cps for fluorine

nuclei separated by four and five bonds, respectively.

Since that time similar cases for near-zero coupling

between vicinal fluorines in the CF CF2 group have been

reported in the literature (19,20,21). Crapo and Sederholm

(19) first postulated that the near-zero coupling constants

come about as a result of averaging non-zero coupling

constants over the three stable configurations with respect

to rotation about the connecting carbon-carbon bond.

Subsequently, Petrakis and Sederholm (22) have shown this

idea to be non-valid, since such accidental averaging would

lead one to predict that the coupling constants between

vicinal fluorine in all compounds having the CF-CF2 group

would be nearly zero, which is not the case. They concluded

that the coupling constants between fluorine atoms in

saturated organic compounds can be explained if one assumes

that coupling takes place primarily directly through space

rather than through the bond. According to this "through-

space" mechanism, fluorine atom coupling is almost completely











due to direct overlap of orbitals on the two fluorine atoms.

Sederholm and Petrakis further postulated that coupling

constants become zero when the distance between fluorine
0
atoms become greater than 2.72A, approximately twice the

Van der Waals radius for the fluorine atom. In the CF3CF2

group the calculated internuclear distance between two

fluorine atoms on adjacent carbons is greater than 2.72A.

However, if one considers the F-C-C-F coupling

constants in a substituted ethane, it is apparent that if

the trans constant is as great as that for the gauche

relationship, the major part of the coupling could not be

transmitted through space. For example, the trans coupling

constant for CF2BrCFBr2 (23) is 16.2 cps and the gauche

coupling constant is 18.6 cps. Also, if one considers the

system CF -CFXY, one finds results for the F-C-C-F constants

as follows: CF CH2F (24) 15.6 cps, and CF3-CFC12 (25) 5.7

cps. These results are certainly not easily explained if

one agrees that the "through-space" mechanism is the only

mechanism for vicinal fluorine-fluorine coupling.

Recently, Ng and Sederholm (26) have explained the

above mentioned results on the basis of two fluorine-fluorine

spin coupling mechanisms; the "through-bond" and the

"through-space" mechanisms. The "through-bond" mechanism

proceeds through the electronic structure in the intervening

bonds, as is the case with proton coupling, whereas the










"through-space" mechanism becomes operative only when there

is direct overlapping of the electronic clouds of the

fluorine atoms. They postulated that in the case of vicinal

fluorines only the "through-bond" mechanism is important

and that the magnitude of the "through-bond" coupling is

governed by the electron withdrawing power of the other

substituents attached to carbon skeleton which can cause the

coupling to vanish. When fluorine nuclei are separated by

more than three bonds, the coupling, though diminishingly

small from the "through-bond" mechanism, may be enhanced if

the geometry of the molecule allows the nuclei to get into

close proximity so that the "through-space" mechanism

becomes operative.

It is generally agreed that fluorine-fluorine

couplings do proceed by more than one mechanism. Now, the

principal problem that is to be solved is the relative ex-

tent to which fluorine-fluorine couplings are transmitted

by overlap of the p electrons of one fluorine atom with

another fluorine atom not directly bonded to the first, or

alternately, by polarization of the electrons occupying the

intervening bond orbitals.

In addition to unravelling the subtle nature of

fluorine-fluorine coupling constants, there are as yet many

other problems concerning fluorine-fluorine couplings in

fluorocarbons and fluorocarbon derivatives which remain to











be investigated. Two such problems are the effect of dif-

ferent substituents and the effect of temperature on the

fluorine-fluorine coupling constants in certain fluorocarbon

derivatives. The object of such investigations would be to

lend insight into the effect of molecular geometry and

molecular motion on the coupling constants and chemical

shifts.

The dependence of nuclear spin-spin coupling constants

upon molecular geometry is of considerable interest and

importance. The theoretical work of Gutowsky, Karplus, and

Grant (15) on the angular dependence of electron coupled

proton interactions in the CH2 group has led to calculated

results which are in general agreement with experimental

results. The results were calculated from a valence bond

treatment and were made for static molecules in their

equilibrium configuration. They showed that the geminal

coupling constants decrease with increasing H-C-H' angle.

Gutowsky, Mochel, and Somers (27) have further

postulated that because the predicted angular dependence of

the coupling is nonlinear, the bond-bending vibrations

should give an average for the H-H and H-F coupling constants

in the CH2 and CHF groups, respectively, which is appreciably

larger than that for the corresponding equilibrium, but

static, angle. The detection of this averaging effect requires

that the vibrational amplitudes be modified. Gutowsky (27)










suggests that this may be accomplished either by changing

the temperature of a sample or by isotopic substitution.

Several isotope effects upon chemical shifts have been

observed in the high-resolution nuclear magnetic resonance

spectra of H1 and F19 nuclei (28,29,30,31,32,33). Such

observations led to the suggestion (27) that the difference

in vibrational amplitudes is the primary cause of the

isotope chemical shifts, and that there might also be

observable vibrational effects upon electron coupled

nuclear spin-spin interaction.

Petrakis and Sederholm (22) have found that chemical

shifts of various gaseous compounds vary with temperature.

This effect was ascribed to excitation of vibrational modes

of the molecules, the protons in the excited molecules

being differently shielded than the protons in the ground

vibrational state. Schug, McMahon and Gutowsky (34) have

done theoretical calculations for the temperature depen-

dence of the proton-proton coupling in substituted ethanes.

They found that torsional vibrations produce a slight

temperature dependence of opposite sign for the trans and

gauche coupling. However, for molecules in which the

potential function has threefold symmetry, rotational

averaging leads to a cancellation of the vibrational effects,

giving a temperature independent value for the average

coupling. This prediction was experimentally verified on










ethyl nitrate for which the proton-proton coupling constant

was found to be invariant over a 1000 temperature range.

Gutowsky, Belford and McMahon (35) have observed the

H1 and F19 magnetic resonance spectra of several poly-

substituted ethanes over temperature ranges of 2500 to

4500K. By assuming that the temperature dependence of the

chemical shifts and coupling constants results only from a

change in the equilibrium concentration of the rotamers,

they were able to calculate the relative energies of the

different rotamers. Similar investigations using the above

assumptions, have been done by Fessenden and Waugh (36) and

Abraham and Bernstein (37).

A second method of calculating the potential energy

as a function of internal rotation in substituted ethanes

was proposed by Thompson, Newmark and Sederholm (38). They

utilized the Boltzmann energy distribution to calculate the

free energy associated with the various rotamers from their

integrated areas as obtained from the fluorine magnetic

resonance spectra at various temperatures.

Most of the work in the literature dealing with the

effects of substituents on fluorine-fluorine coupling

constants in fluorocarbon derivatives is concerned with the

dependence of the coupling constants on the electro-

negativity of the substituents attached to the carbon

skeleton. Dyer (59) has shown that the fluorine geminal











coupling constants in substituted ethanes vary widely in

magnitude and are dependent on the electronegativity of the

third substituent attached to the carbon atom. Ng and

Sederholm (26) have reported that the vicinal coupling

constants in a series of halogen substituted ethanes and

propanes are inversely proportional to the sum of the

Pauling electronegativities of the substituents. This,

they say, suggests that highly electronegative substituents

withdraw the excited triplet or T state electrons, which

are responsible for the transmission of nuclear spin

information, from the bonds between the interacting nuclei,

thereby reducing the coupling constants.













INTRODUCTION


In order to undertake a study of any fluorocarbon

derivatives, such as the trifluorovinyl derivatives, one

must take into consideration fluorine chemical shifts and

fluorine spin-spin coupling constants. As yet, the

theoretical work that has been done on these two NTR

parameters is limited and, therefore, some of the experi-

mental results are ambiguous. However, a great deal of the

experimental work done on both parameters has, in some

instances, led to important information concerning the

nature of the F19 chemical shifts and the F19 F19 coupling

constants. Also, the experimental work done on substituent

effects and temperature-dependent effects show much promise

with regard to molecular geometry and molecular motions.

Much of the earlier work (40,41,42) related to the

trifluorovinyl group has been very limited. The only

conclusion that can be drawn from this earlier work is that

the chemical shifts and coupling constants of the three

fluorine atoms are quite sensitive to the nature of the

substituent to which the trifluorovinyl group is attached.

As yet, no correlations have been made between the two NMR

parameters and substituent effects. The only temperature

dependent work done on any trifluorovinyl derivatives was










carried on by Ramey and Brey (43). This work was limited

to perfluoropropenyl halides.

The primary purpose of the present investigation

was twofold: 1) to determine experimentally the effect of

substituents upon the F19 chemical shifts and F19 F19

coupling constants within the trifluorovinyl group, and 2)

to determine the effect of temperature change upon F19 F19

coupling constants.

The secondary purpose was to attempt to relate the

observed changes to the mechanism of transmission of spin-

spin coupling and to changes in molecular conformation.












EXPERIMENTAL AND EXPERIMENTAL RESULTS


Experimental


The spectra were obtained with a Varian spectrometer

operating at 56.4 mc./sec. Audio-frequency modulation of

the magnetic field was used to produce sidebands, the

frequency of which was continuously monitored by a Hewlett-

Packard 523B frequency counter. From eight to ten

replications of the spectrum were graphically recorded, and

the frequency separations were calculated from the averaged

distances measured from the chart paper. Chemical shifts

were obtained by substituting a tube of trifluoroacetic

acid in the probe while sweeping the field continuously

through the resonances of the reference and of the sample.

The temperature of the sample was regulated by

adjusting the flow rate of dry nitrogen passing through a

Varian V 4340 variable temperature probe assembly. For the

low-temperature measurements, the nitrogen was cooled by

passing it through a copper coil immersed in liquid nitrogen.

A copper-constantan thermocouple placed within the Dewar

insert was used to determine the temperature, which was

considered accurate to within + 20.

The difficulties encountered in obtaining a homo-

geneous field at the lower temperatures were overcome by










the use of a standard sample. An olefin exhibiting promi-

nent fine structure was used to adjust the field.

The silanes studied in this investigation were

prepared by W. H. Oliver of this department, and the fluoro-

propenes by Dr. J. Savory (44). The remaining trifluorovinyl

derivatives were prepared by Dr. D. Sayers of this department

and by the research division of Peninsular Chemresearch,

Inc., Gainesville, Florida.


Experimental Results


From a consideration of the generalizations as

derived from previous work (40,41,42) on the nuclear spin-

spin coupling constants in fluorolefins, it is possible to

assign unambiguously the multiplets corresponding to the

various nuclei. These generalizations are: 1) Jtrans

is much larger than Jcis in all reported cases; 2) Jgem

is usually larger than Jcis but less than Jtrans' and 3)

the chemical shift of Fx in the molecule FaFbC=CFx, is at

higher field than those of Fa and Fb. All the compounds

studied have first-order spectra so that the coupling

constants may be obtained directly from multiple sepa-

rations.

In Tables 1 and 2 are given the chemical shifts and

coupling constants within the trifluorovinyl group for the

several compounds as neat liquids at room temperature. The









U) C'0- cO D 0 cO
ft N * * * -
0 o io K K ;d- L Nj- o 17
r- H r-l r-c i- J r- OH








+0 0




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0 h0 0o








MO
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H o O O O CP- ,-4- CO O O -P










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l '4 0 PA f

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MU >i rd d C








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H
0

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^H







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0 d- 0 r-H C\N C\ -
r-l r-H C- C- C CV C


18




0







4-
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-P
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Co







-p













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several compounds have been divided into three groups for

a particular reason which will be explained later. Room

temperature values for the geminal coupling constants, Jab'

and the values for the chemical shift of F for the various
a
compounds are plotted in Figure 1.

In Table 3 are listed the room temperature values

for the cis coupling constant, Ja, the values for the

chemical shift of Fx, and the Pauling electronegativity of

the substituent atom directly attached to the trifluorovinyl

group. Jax and the chemical shifts of Fx are plotted

against electronegativity values in Figures 2 and 3,

respectively.

Values for the cis coupling constants, Jax, and Jab

over a range of temperatures are listed in Tables 4 through

9 and are plotted in Figures 4 through 9. The changes of

the values with temperature are usually fairly small; how-

ever, they seem clearly to be significant.

Values for the trans coupling constants, Jbx' over

a range of temperatures are listed in Tables 10 through 12

and are plotted in Figures 10 through 12. The trans

coupling constant appears to be insensitive to temperature

change in all compounds studied.












120



-OCH2CF3

100 -(CH2)2Si(CH5) 3

o
O-H O-OCF3

80 o-C1

ab *-Si(CH3)3
cps
e-I
60 *-CF3




40
o Group I compounds
*-SCF, o Group II compounds
e-CN Group III compounds

20



S-COF
I I I I I
0 10 20 30 40 50
Chemical shifts of Fa ppm

Fig. 1.-The correlation between Jab and the chemical
shifts of Fa observed in some of the tri-
fluorovinyl compounds.












TABLE 3


CORRELATION OF J AND THE CHEMICAL SHIFTS OF F WITH
ax x
ELECTRONEGATIVITY OF THE SUBSTITUENT ATOMS


THE


Chemical
Substituent Pauling* shift of Fx'
atom electronegativity ax, cps ppm

Si 1.8 25.4** 122*
B 2.0 24 107
H 2.1 33 105
C 2.5 35.3** 105**
S 2.5 41.7 76.5
I 2.5 52.2 71.8
Br 2.8 57 --
Cl 3.0 58 65
0 5.5 61.5** 62.8**
*
Values obtained from reference 45.
**
Average values obtained from values for those
compounds containing the same substituent atom listed in
Tables 1 and 2.



















120 -Si





S105 B C

0
-P

' 90 -




OS
00
*I


*O
60-




45 I I I I
1.5 2.0 2.5 3.0 5.5 4.0

ppm Pauling electronegativity

Fig. 2.-The correlation between the chemical shifts of Fx
and the electronegativity of the substituent atoms
observed in some of the trifluorovinyl compounds.








25


70-



S0
*O
60-
Cl
Br


*I
50

J
ax

cps
40- *s


eC
*H
30-


eSi
*B-

20-




10I I
1.5 2.0 2.5 5.0 3.5 4.0
Pauling electronegativity

Fig. 5.-The correlation between Jax and the electronega-
tivity of the substituent atoms observed in some
of the trifluorovinyl compounds.










TABLE 4


THE TEMPERATURE DEPENDENCE OF Jab OBSERVED IN SOME
TRIFLUOROVINYL COMPOUNDS OF GROUP I



F Y
b

Y = -(CH2)2Br Y = -(CH2)2CF=CF2 Y = -(CH2)2Si(CH3)5

Temp. Jab Temp. Jab Temp. Jab
o0 ao ab o0 0

86 85.0 + 0.1 32 91.4 + 0.1 82 93.1 + 0.2
55 84.7 + 0.2 -19 91.2 + 0.2 60 92.8 + 0.2
32 84.8 + 0.2 -52 91.1 + 0.1 32 92.5 + 0.1
-10 84.6 + 0.2 -90 91.0 + 0.3 -38 92.1 + 0.2
-55 84.5 + 0.1 -105 91.0 + 0.3 -78 91.8 + 0.2










TABLE 5
THE TEMPERATURE DEPENDENCE OF Jab OBSERVED IN SOME
TRIFLUOROVINYL COMPOUNDS OF GROUP II



F Y
~ =/FX

bC\


Y = -OCF3 Y = -OCH2CF
Temp. Jab Temp. Jab
OC C
32 87.5 + 0.1 32 101.6 + 0.1
-10 87.0 + 0.1 -10 101.3 + 0.2
-28 86.7 + 0.1 -30 100.9 + 0.1
-63 86.4 + 0.2 -72 100.6 + 0.2
-105 85.7 + 0.2 -115 100.1 + 0.2











TABLE 6

THE TEMPERATURE DEPENDENCE OF Jab OBSERVED IN SOME

TRIFLUOROVINYL COMPOUNDS OF GROUP III


C = C

b


Y = -SCF3

Temp. Jab
C


Y = -Si(CH )2H

Temp. Jab
0C


Y = -Si(CH )

Temp. Jab
C


52 30.4 + 0.1 55 69.0 + 0.2 86 72.0 + 0.1
-5 29.7 + 0.1 32 68.5 + 0.1 57 71.8 + 0.1
-25 29.3 + 0.1 -10 68.0 + 0.1 52 71.6 + 0.1
-65 28.5 + 0.1 -55 67.7 + 0.2 -33 70.8 + 0.2
-105 28.1 + 0.1 -92 67.0 + 0.2 -97 70.1 + 0.1











TABLE 7
THE TEMPERATURE DEPENDENCE OF J OBSERVED IN SOME
ax
TRIFLUOROVINYL COMPOUNDS OF GROUP I



F Y
b


Y = -(CH2)2Br Y = -(CH2)2CF=CF2 Y = -(CH2)2Si(CH 3)

Temp. J Temp. J Temp. J
oC ax oC ax oC ax

55 33.3 + 0.0 32 32.5 + 0.1 82 32.6 + 0.1
32 32.9 + 0.1 -19 31.9 + 0.1 60 32.2 + 0.1
-10 32.5 + 0.1 -52 31.6 + 0.2 32 31.9 + 0.1
-55 31.8 + 0.1 -90 30.6 + 0.2 -38 30.9 + 0.1
-98 30.9 + 0.1 -70 30.1 + 0.1
-96 29.8 + 0.2











TABLE 8

THE TEMPERATURE DEPENDENCE OF J OBSERVED IN SOME
TRIFLUOROVINYL COMPOUNDS OF GROUP II

b /x

F Y
b


Y = -OCF3
Temp. J
o 0ax


Y = -OCH2CF3
Temp. J
oc


32 65.1 + 0.2 32 57.8 + 0.0
-10 65.0 + 0.0 10 57.6 + 0.1
-28 64.8 + 0.1 -30 57.5 + 0.1
-63 64.7 + 0.2 -52 57.3 + 0.1
-105 64.4 + 0.2 -72 57.2 + 0.2
-115 56.5 + 0.1










TABLE 9

THE TEMPERATURE DEPENDENCE OF J OBSERVED IN SOME
ax
TRIFLUOROVINYL COMPOUNDS OF GROUP III

a / x
Fa,_C = C/Fx


b


Y = -SCF Y = -Si(CH )2H Y = -Si(CH3)
Temp. J Temp. J Temp. J
oC ax oC ax oC ax

32 41.7 + 0.2 55 25.8 + 0.2 86 26.5 + 0.1
-3 41.4 + 0.1 52 25.6 + 0.2 57 26.1 + 0.1
-25 41.2 + 0.1 -10 25.0 + 0.1 32 25.9 + 0.1
-65 40.8 + 0.1 -55 24.6 + 0.2 -33 24.8 + 0.2
-105 40.2 + 0.1 -92 23.8 + 0.1 -97 23.9 + 0.1

















rI I

io





. I O
CC\
,0 0








X o


H



m o







o
I. 00
0M b






O 0
,0
SI 0 0 -0 0





Cd 0





O d
'.0







N *H
rc!
E-A
l d Po







I I i C R
a a o CO
l 0 -)

l I
l r
















0
ON
oCT I
o0
m o
0 0
C\J

o 0o
I 0 0 -i

0




0
0 0

o







-d \0


00
oo
o H
O i H







O 0

OI 0P
C00


ra O

so



O 0
I *H


O U


II \C -P -
c 0 0 D 4 I
O O 0 0 c0



S00














o0\ 0

O
.- r
C.)

I I O a


III



o
O




0-0 4
-I-











4 **
0





E- l







O
O 0




0 ,O
aI h
S.-4




G r


O H
a












o o







O K\




SO 0 C

,O o
\ \O \
\ ~~ \ Y^
t \ *0




















NW K
0 0

q 0 C/



0 0 0

I I I



0 0 0
O Fr Orl
I I I1
II 11 n
r\ >-i

0 0U


X o
c o


0
oN I
a p
o

,--I
0



o
rn
*41
OD P









0
a,





0






OO






do 0

CO






(o

0
Ob









N 0(1)







I
0


a'l
o o




v-a

Eo
QPr-

0 >-
C CQ ri
1 !-

E- >O
*Ur
[>-


CO
OJ


I

























0


I














































I I
10 --
<> d-


I I-
co U
CO Lf


o' I
0
0

r

0o
o


0



O


01 0

,0
0
o o
o



O IO
o H



Cd0
O


I


o

QO

0
0 cd


o o

o o







0 hI
o ^^


C)3















0 O

0 00 0
\ 0 0






0 o
MI-
1 I1




\ ro













) OHb
0 p H
0- 0

ON
0 -
ON
S1-0

0*5
oo

O a














0 P, I
IO








o bp

\ \ 0 h 0I
\ \\9 fe
\ \ IJ?0








36 '


TABLE 10

THE TEMPERATURE DEPENDENCE OF Jbx OBSERVED IN SOME
TRIFLUOROVINYL COMPOUNDS OF GROUP I

aNC = C/x

F Y
b


Y =-(CH2)2Br Y = -(CH2)2CF=CF2 Y = -(CH2)2Si(CH3)3
Temp. J Temp. J Temp. Jb
oC bx o b oC bx

32 113.7 + 0.4 86 113.9 + 0.2 82 113.8 + 0.4
-19 113.8 + 0.4 32 113.8 + 0.4 32 115.9 + 0.3
-52 113.6 + 0.5 -10 114.0 + 0.4 -38 113.9 + 0.4
-90 113.7 + 0.4 -55 113.8 + 0.6 -70 113.8 + 0.5
-98 113.6 + 0.6 -96 113.8 + 0.7











TABLE 11

THE TEMPERATURE DEPENDENCE OF Jbx OBSERVED IN SOME

TRIFLUOROVINYL COMPOUNDS OF GROUP II
F F
a /x
C = C
Fb


Y = -OCF
Temp. Jb
oC
32 111.0 + 0.4
-10 110.5 + 0.6
-28 110.5 + 0.5
-63 111.0 + 0.6
-105 111.5 + 0.5


Y = -OCH2CF3
Temp. Jbx
C bx
32 106.8 + 0.4
10 106.4 + 0.2
-30 106.4 + 0.4
-72 106.2 + 0.5
-115 106.6 + 0.5










TABLE 12
THE TEMPERATURE DEPENDENCE OF Jbx OBSERVED IN SOME
TRIFLUOROVINYL COMPOUNDS OF GROUP III

Fa /Fx
F Y
b

Y = -SCF Y = -Si(CH )2H Y = -Si(CH3)5
Temp. Jb Temp. Jb Temp. Jbx
oC b C x oC

52 122.3 + 0.4 55 117.4 + 0.5 86 116.8 + 0.4
-5 123.0 + 0.4 52 117.5 + 0.6 57 116.7 + 0.4
-25 122.8 + 0.4 -10 117.5 + 0.6 32 117.0 + 0.5
-65 123.0 + 0.5 -55 117.5 + 0.6 -33 117.0 + 0.4
-105 123.0 + 0.5 -92 117.4 + 0.6 -97 116.6 + 0.4




















es
C\J rN

UO









0 0 0
O O


5 II II



C O O


ON
0 I

0




o








o o 0







0
r-I






o o





0 ~o0
to
O E




0
Mdo



'do







o



d)
o g

c0
I-H
o OH



I I

a ro
0 b
ft
0D CH












4->r-
>>r
I> a


8 Q
I-b c)


I I




























0N


O
0

I
II e


I -I
- H-4


*I

0 0
o r-


X co
> o


0 I
So

0
o

,-4


4.
0




-rd
0










O




CI)
1-i





0 ,







,0
0
o
p
O

Oi
00
H
CO
to




0o U

0





0I
O

0
0 0
OH










N .r-



o a
a o
o~
-Pr-

0 S
^ ^
*d

















SO
M

I

>-


II


1 I
O\j 0
Nc OC
r-i r-


-1


I
O)


0


ON I
0
o o



0






CH
00
0










N
O
rO












0 ad
o d













OO
0
0






OH
o





00




Cd
o











I 4E
0 0



C\J
r -

0o o
N r-I






r-1 F4


b












DISCUSSION


The results of greatest importance in this work are:

1) the extreme sensitivity of the geminal coupling constants,

Jab' and the chemical shifts of Fa to the conjugating ability

of the substituent, -Y; 2) the dependence of the cis coupling

constants, Jax, and the chemical shifts of Fx on the electro-

negativity of the substituent atom which is directly attached

to the trifluorovinyl group, and 3) the temperature depen-

dence of the coupling constants Jab and Jax

The trans coupling constants, Jbx, appear to be

insensitive to both the nature of the substituent and the

temperature. The chemical shifts of Fb do not correlate

with any specific property of the substituents.


Effect of Conjugation on Jab and the Chemical Shifts of Fa


From an analysis of the chemical differences among

the substituents and from the values of the chemical shift

for Fa, it is possible to divide the compounds into three

main groups, as listed in Tables 1 and 2. In Group I,

there are seven compounds, each of which has a substituent

group that would not be expected to enter into conjugation

with the trifluorovinyl group. The values of the chemical










shift for Fa of these compounds range from 23 ppm to 30.4

ppm. The corresponding values for Jab range from 78 cps

to 92.5 cps.

In Group II, there are two compounds, CF2=CFOCF3

and CF2=CFOCH2CF3. Both of these compounds have a

substituent group which could enter into conjugation by

contributing electrons to the trifluorovinyl group. Such

a mechanism should increase the electron density at Fa over

that of the compounds in Group I. This point is supported

by the fact that the chemical shift values for F in these
a
two compounds are 10 ppm to 23 ppm higher than the values

for the compounds in Group I. Another point of importance

is the fact that the chemical shift value for F in
a
CF2=CFOCH2CF3 is about 6 ppm higher than that in CF2=CFOCF3.

As would be expected, the separation of the oxygen from

the highly electronegative trifluoromethyl group by a

methylene group has facilitated the ability of the oxygen

to donate electrons. The values for Jab are 87.5 cps and

101.6 cps, the higher value belonging to CF2=CFOCH2CF3.

In Group III there are 13 compounds, each of which

has a substituent group which could enter into conjugation

by withdrawing electrons from the trifluorovinyl group.

Such a mechanism should decrease the electron density at F
a
in the compounds of Group I. This decrease should, of

course, be more pronounced in comparison to the compounds of










Group II. Both of these points are supported by the fact

that chemical shift values for Fa in the compounds of Group

III are 7 to 37 ppm lower than those of Group I, and 21 to

53 ppm lower than those of Group II.
The above proposal that the different substituents

in Group III are capable of withdrawing electrons from the

trifluorovinyl group can be rationalized as follows: 1)

the ability of sulfur, iodine and silicon (46) to withdraw

T electrons from an unsaturated system to which they are

bonded by utilizing vacant d orbitals, 2) the ability of

the highly electronegative groups, -CF3, -CF2C1, and -CF2Br

to participate in double bond-no bond resonance (47), 3)

the ability of B to accept T electrons into its vacant 2p

orbital and 4) 1,3 conjugation in CF2=CFCOF and CF2=CFCN.

Of the compounds listed in Table 2, CF2=CFCOF has

the second lowest chemical shift value for Fa, 0.6 ppm,

and the second lowest Jab value, 6.0 cps. In comparison to

the other compounds of Group III, this compound should,

therefore, be highly conjugated. This prediction is veri-

fied by the fact that there are two NMR-distinguishable

isomers at 1050C, because of restricted rotation about the

central bond of the conjugated system (48).

The effect of conjugation on Jab seems to be related

to the electron density at Fa, since, as shown in Figure 1,

the coupling constants Jab increase regularly with an










increase in the value of the chemical shift of Fa. One

possibility is that a decrease in electron density at F

may cause an increase in the Fa-C-Fb bond angle, thereby

producing a decrease in Jab (assumed to be positive), if

the coupling operates through the bond in the same way as

for H-H geminal coupling (15) and/or if the coupling

operates by a "through-space" mechanism similar to that

proposed by Sederholm (22,26). Therefore, if this is the

case, no specific proposal can be made concerning the

mechanism of the coupling, but it would mean that compounds

in Group III probably have larger values for the F -C-Fb

bond angle than compounds in Group I or Group II and that

within Group III, the more highly conjugated compounds

probably have the larger values for the Fa-C-Fb bond angle.

However, if Jab is assumed to be negative, then an increase

in the Fa-C-Fb bond angle causes an increase in the magnitude

of Jab; where, in this instance, an increase in magnitude is

the same as an algebraic decrease in Jab. This increase in

Jab with increasing angle would lead one to believe that
the coupling operates almost solely by a "through-bond"

mechanism similar to that in H-H geminal coupling (15),

since an increase in the Fa-C-Fb bond angle should result in

a decrease in Jab if coupling operates by a "through-space"

mechanism (22,26). Also, based upon the above hypothesis,

the order of values for the F -C-Fb bond angle for the
a b










various compounds would be reversed from that proposed

above.

Another possibility is that a decrease in electron

density at Fa may cause a decrease in the Fa-C-Fb angle.

This assumption would lead to additional arguments con-

cerning the Fa-Fb coupling mechanism depending again on

whether Jab is assumed to be negative or positive.

Still, another possibility is that a decrease in

electron density at Fa may mean that some of the electrons

that actually transmit the coupling information between F
a
and Fb are being withdrawn. Such a proposal would lead one

to believe that the geminal coupling operates almost solely

by a "through-bond" mechanism. Also, this would lead one

to believe that the ( electrons in the C-Fa bond are being

withdrawn rather than the n electrons around Fa, since

compounds of Groups II and III do conjugate, but with an

opposite effect on Jab.

Although the answer to this problem awaits further

evidence, it can be stated with reasonable assurance that

the chemical shift values for Fa and the values for Jab

are directly related to the degree of conjugation in tri-

fluorovinyl derivatives of the type F bFC=CFxY.










Dependence of the Chemical Shifts of Fx and Jax on

the Electronegativity of the Substituent Atoms


From a comparison of the different substituents with

the chemical shifts of F and the coupling constants, Ja',

it is possible to correlate both parameters with the

electronegativity of the substituent atom directly attached

to the trifluorovinyl group.

As pointed out in Table 3 and Figure 2, the shift

of the geminal fluorine Fx goes regularly to lower fields

in the series Si to O, with some 60 ppm difference between

the extremes. This trend is parallel to that found for

binary fluorides (3,4): The more electronegative the

attached atom, the greater the downfield shift. A similar

trend is found in the series CFH3, CF2H2, CF3H and CF ,

where successive replacement of H atoms of methane by the

more electronegative F atom causes a progressive displace-

ment of the fluorine resonance to lower fields (5).

The downfield shift of Fx (a decrease in the values

of the chemical shift) means that Fx is magnetically un-

shielded as the electronegativity of the substituent atom

increases. This may mean that the electron density of F

is decreasing as the electron withdrawing power of the

substituent atom increases. It could also mean that the

covalent character of the C-Fx bond is increasing as the









electronegativity of the substituent atom increases, since,

as pointed out by Saika and Slichter (2), the paramagnetic

contribution to fluorine chemical shifts is largest for

covalent bonds. An increase in the covalent character of

the C-Fx bond in this instance could be explained as follows:

The more electronegative substituent atoms withdraw electrons

from the vicinity of C, followed by back donation of elec-

trons from F to C.

It is apparent from Figure 2, that the electronega-

tivity of the substituent atom is not the sole factor which

affects the chemical shifts of F The most obvious dis-

crepancy is found for substituent atoms C, S, I: All three

atoms have a Pauling electronegativity value of 2.5, but

corresponding chemical shift values for Fx of 108 ppm,

76.5 ppm, and 71.8 ppm. The difference might possibly be

related to the fact that both S and I do enter into conju-

gation with the trifluorovinyl group and both have unshared

pairs of electrons. This abundance of electrons in the

vicinity of the atoms could possibly produce a magnetization

at Fx which is in the same direction as the magnetic field.

This same effect might also be operative in the cases of Cl

and 0, in which case the chemical shift values for Fx are

probably lower than what one would expect solely on the

basis of electronegativity.










As shown in Table 3 and Figure 4, the values for the

cis coupling constants, Jax, increase with an increase in

the electronegativity of the substituent atoms. In

comparison to the trend observed for the chemical shifts of

F this could imply that J increases as the electron

density at Fx decreases. This is in direct contradiction

to what one would predict. However, if one assumes that

increased covalent character of the C-Fx bond accounts for

the increase in the chemical shifts of Fx, then the increase

in the values of Jax with electronegativity could be

rationalized as follows: As electrons are more evenly

distributed between C and Fx it would facilitate the

through-bond coupling mechanism in the system Fa-C=C-Fx.

Although the cis coupling constants, Jax, seem clearly to

be related to the electronegativity of the substituent atom,

it does seem that there are other, less obvious, factors

which affect Jax. This observation is based upon the fact

that the values of Jax are 35.5 cps, 41.7 cps, and 52.2 cps

for C, S, and I, respectively; all have a Pauling electro-

negativity value of 2.5. Since both S and I have unshared

pairs of electrons and both enter into conjugation with the

trifluorovinyl group, may in some way explain why they are

not more in line with C. Either or both of these effects

may also contribute to Jax in the other compounds.
d^C










Temperature Dependence of the Coupling Constants Jab and Jax


The geminal coupling constants, Jab' and the cis

coupling constants, Jax, increase with increasing tempera-

ture, as shown in Figures 4 through 6 and Figures 7 through

9, respectively. This change in coupling constants is small

in both cases, but significant.

The cis coupling constants, Jax, increased about

1.0 to 2.0 cps for a 1500C temperature rise; the change

does not appear to be related to the conjugation or electro-

negativity effects cited earlier.

The geminal coupling constants, Jab, increased about

0.5 to 2.0 cps for a 1500C temperature rise. For compounds

of Group I, this increase in Jax is approximately 0.5 cps,

while for compounds of Group II and Group III, this increase

is about 1.0 cps. Since Group I compounds have substituent

groups which would not be expected to conjugate with the

trifluorovinyl group and Groups II and III compounds do,

might lead one to believe that the temperature dependence

of Jax is somehow related to the temperature dependence of

conjugation (i.e., the fact that conjugation usually in-

creases with decreasing temperature). However, if one

recalls that values for Jax decrease with conjugation for

Group III compounds and increase with conjugation for Group

II compounds, then it would not seem likely that the tempera-

ture dependence of Jax is related to any conjugation effect.










Recently Ramey and Brey (43) have reported on the

temperature dependence of spin-spin coupling constants of

fluoropropenes of the type FaFbC = CFxY, where Y = CF3,

CF2C1, CF2Br, and CF2Br. Since, as postulated above, the

temperature dependence of Jab and Jax does not appear to

be related to any substituent effects, it seems likely

that the arguments advanced by them can be generalized to

apply to any of the trifluorovinyl derivatives studied here.

They postulated that the explanation for the increase in the

values for Jab and Jax with increasing temperatures may lie

in the greater excitation, with increasing temperature, of

molecular vibrations. By assuming that the CF2 deformation

would have the most influence on the temperature dependence

of Jab' they were able to show, by use of the Boltzmann

distribution, that the fraction of molecules in excited

states for this mode is 0.05 at -1000 and 0.26 at +1000.

This significant change in population coupled with the fact

that, for the ground state, the system spends the larger

amount of time near the equilibrium configuration, while

for excited states, it spends most of the time near the

extremes of the vibration, lead them to propose possible

mechanisms for Fa-Fb coupling consistent with the observed

increase in Jab with temperature. They proposed that if the

symmetric in-plane deformation of the geminal fluorines is










strongly anharmonic, then: 1) Jab should be expected to

increase sharply as the atoms approach one another, if there

is a through-space contribution to the coupling constant,

and 2) J~. should again be expected to increase with

decreasing angle if a through-bond contribution to Jab

operates in the same way as for the H-H geminal coupling.

These possibilities were, of course, not meant to

be interpreted as the absolute solution to the problem of

geminal fluorine-fluorine coupling. There is always the

possibility that the two contributions may operate

simultaneously. Any other possibility would also have to

tke into account the symmetry or asymmetry of the potential

well for the symmetric in-plane deformation of the C 2 group

and the relation of Jab to the position of the atoms, a

and Fb-

Although it is not possible to make any specific

prediction concerning the mechanisms of the fluorine-fluorine

coupling, it does, however, seem likely that the temperature

dependence of Jab and Jax is related to vibrational excita-

ticn in the trifluorovinyl derivatives.












SUMMARY


A variety of trifluorovinyl derivatives of the type

F FbC = CFxY have been examined and the following correla-

tions have been drawn between the observed NIR parameters

and the substituent, Y: 1) Fa chemical shifts and Jab

coupling constants depend on the conjugating ability of Y,

2) Fx chemical shifts and Ja coupling constants depend on

the electronegativity of the directly attached substituent

atom, and 3) Fb chemical shifts and Jbx coupling constants

are not related to any specific property of the substituent.

The temperature dependence of the spin-spin couplings,

Jab and Jax, has been attributed to the excitation of
vibrational modes in the molecules and has been found to

be independent of the nature of the substituent.

Both the temperature dependence and the substituent

dependence of the coupling constants, Jab, have led to many

alternative explanations which might shed some light on the

mechanism of F19 F19 geminal coupling constants. As yet,

no definite conclusions have been reached, but it is felt

that the geminal coupling does probably proceed by the

"through-space" and "through-bond" mechanisms, simul-

taneously.








54

Also, no definite conclusions have been reached

concerning the molecular geometry of the trifluorovinyl

group, but additional theoretical work on the mechanism of
19 19
F F19 geminal coupling would probably make it possible

to make some good predictions concerning the value of

Fa-C-Fb bond angle.











LIST OF REFERENCES


1. W. E. Lamb, Jr., Phys. Rev. 60, 817(1941).
2. A. Saika, and C. P. Slichter, J. Chem. Phys. 22,
26(1954).
3. H. S. Gutowsky and C. J. Hoffman, Phys. Rev. 80,
110(1950).
4. H. S. Gutowsky and C. J. Hoffman, J. Chem. Phys. 19,
1259(1951).

5. L. H. Meyer and H. S. Gutowsky, J. Phys. Chem. 57,
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BIOGRAPHICAL SKETCH


Charles Glen Moreland, Jr. was born November 24,

1936, at St. Petersburg, Florida. In June, 1955, he was
graduated from St. Petersburg High School. In June, 1957,

he received the degree of Associate of Arts from

St. Petersburg Junior College, and in February, 1960, he

received, with honors, the degree of Bachelor of Science

in Chemistry from the University of Florida.

In February, 1960, Mr. Moreland entered the Graduate

School of the University of Florida. He worked as a

research assistant in the Department of Chemistry until

September, 1960, when he received a National Defense Act

Fellowship. He received the degree of Master of Science

with a major in Chemistry in June, 1962. From June, 1962,

until the present time he has pursued his work toward the

degree of Doctor of Philosophy with a major in Chemistry.

Charles Glen Moreland is married to the former Nancy

Louise Park and has one son, John Calloway. He is a member

of the American Chemical Society and Phi Beta Kappa Honorary

Fraternity.










This dissertation was prepared under the direction

of the chairman of the candidate's supervisory committee

and has been approved by all members of that committee. It

was submitted to the Dean of the College of Arts and

Sciences and to the Graduate Council, and was approved as

partial fulfillment of the requirements for the degree of

Doctor of Philosophy.


August 8, 1964


Dean, College/of ArPs and Sciences



Dean, Graduate School


Supervisory Committee:


Chairman




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