Title Page
 Table of Contents
 List of Tables
 List of Figures
 Introduction and review of the...
 A comparison of the leuckart...
 A summary of the factors affecting...
 A proposed mechanism
 The proof of the proposed...
 Experimental details
 Summary and conclusions
 Biographical items

Title: mechanism of the Leuckart reaction ...
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Creator: Young, David Caldwell,
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Table of Contents
    Title Page
        Page i
    Table of Contents
        Page ii
    List of Tables
        Page iii
    List of Figures
        Page iv
    Introduction and review of the literature
        Page 1
        Page 2
        Page 3
        Page 4
        Page 5
    A comparison of the leuckart reagents
        Page 6
        Page 7
        Page 8
        Page 9
    A summary of the factors affecting the reaction
        Page 10
        Page 11
    A proposed mechanism
        Page 12
        Page 13
        Page 14
        Page 15
    The proof of the proposed mechanism
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 27
        Page 28
        Page 29
        Page 30
        Page 31
        Page 32
        Page 33
        Page 34
        Page 35
        Page 36
        Page 37
        Page 38
    Experimental details
        Page 39
        Page 40
        Page 41
    Summary and conclusions
        Page 42
        Page 43
        Page 44
        Page 45
    Biographical items
        Page 46
        Page 47
Full Text

ZiWT or
LIS!D fiF FICRHmS . . ...............
I tmmmtOB Mm mmmi o?-mm umumm ft' '
A (MiffilSOJ! 03" SHB 13WSK35 . #
IV A PROPOSED ratt&JVBtSR. ......... *
n ismmmm mams. .......... # .
VII SOft-UHr /2H> CQIISL'OSXOSS ......... #
Ti OLI Oi'rTl'* J-7!Y. .........**..
ACK2T0'jaK0JirCTG ........................
BIOGRATHtCAl, .....................

X Ta Sffect of F-eiaoval of Water v&tm Beaetioa
^k.tpeyatuye Yield* ...*..>..* 7
II A Coupsriaoa of Reagents at 135 ............ ?
Ill Lot; eitporatur* J*uete.ri Jteoctioaa............ 8
IT Bate Constanta. of the ? Kinsties of tlia I*ad6Ba?tiSeacfeioii. ............ 22
1 Kinetics of the Louefc*t Function. ............. 23
Til JCia:ties of the Xeueitert Basctiea. ............. 23
fill Kinetics of tlia Lcniekart Iteaction. ............ 24
IX Ktaeties of the ^guetoasi S&actioa. ............ 25

use of noam
% Kinetics of the ticrocfeart llcactioa. .......... 19
2 ; Kinetics of tlw Xiouclaart Reaction. .......... 20
3 Ultrts-virolot Al)9orption. ............... 29
if Ultra-violet Absorption of tits Lcwekarfc
Kesction Itixtitro .................. 30
5 tatm-irioXet Absolution of tlto lmu&s&%.
action. Ilissfcw ........ . . .....*. 32
6 Polrjrogren of ffetlisl IsoMtyl Ketone in
JlthiTO} Chloride .................. 35
7 Polca?o$es!tts in 0.1 |l f otraiaott^L Jtaoaim BrosMiu .3?

Chapter I
fh otert reaction is perhaps beet defined m a process for the reductive aiain&tioa of aMehydes or ketones T>y ferjsssii&e, anrsoniam formte, or fonaic acid t.lth forn&oide. he reaction is carried oat hy heating a atxtcam of the caatagri ea^peBead and the ar&de or its derivative* frSsary sad secondary casinos predaeed i the reaction- are obtained as the foray! derivatives! tertiary tsa&mtt are o"btaiaed as the forkatce. tEhe reaction can he illustrated hy the following general cjaatioaet
SR*CO + 21C0^S% * M the reactioa was discovered "by leucfcart,1 uho in 1885 wport-ed the results of an attest to prepare l^easylideaedifoiwdde "by heating hoaealde%de femsside. Instead of the e3g>eetad product, he ohteiaed tMmsyleMne. dihoasylaiaiae. sad trihea^lisBiae# ae well as the foray! derivatives of the first two. tooalaa forcsate tiaa found to react in the ease way as the aide; and hensopheaone could to used la place of the aldehyde, nltho\t# the conditions for the reaction trere eoBewhat mm drastic.

In the years following, Ufiu8&t&a& veskti aaialy with are--
n&tte aldehydes cad teteaeet iMlatSi^*1^ and Eisner cKplled there-
action to pliphatie careenyl cogpouado.
rate mthed receive!, little further attention until 1936, **sea Infersell^ and Me associates reviewed the abject sad applied tlie reaction to the eyntheels of sa'batitatei a-phti$ftethyl *aaiae8# Aaooft fifty papers and one reviet^* hare heea ptibliateA on the subject since W$$*
In spite of this quantify of.wJc, there is little agreeaeai coacernittg; the tmtiiimim of the reaction aeons the mrteaza in the field, la fact, there has heea no puhliohed hypothesis tfliielt eovers taer than the first steps.
Wailach?-3 proposed that the initial steps of the reaction are as follows!
3?ornic acid then reduces this product to -the amine., uhioh. sutssefoent-ly reacts with mere fonaic acid to give the final producta mx%stitttte& fornifiBide.
IWC (OH) 23Eg 4* HCOGB - I&tCBESg 4> RgO 4- COg
J$.*tSlJBg 4- HCOOS ** 1EC3EHCH0 4- BgO
Uovelli5? later ehou& that the reaction 'Ottgd It uwd to pro-r secondary aminos 1>y reacting wamwSmHtateit tmxsmMm with Saetsaet.

Crosslcy and Hockm^ published in a very excellent paper in tt&ca. they reported a eet^arisen of the efficiency of the various reaetaats ^Mea ray he used in the leuc&srt reaction, they reported that forsaaai&e, ixmrnn!bm f ornate, a Mixture of foraarade and fors&c acid, or a mixture of tomuaide said omentum forest "he used with a aarhet^i coiapsund to give the reaction and that the nixturo of fomaaide and formic acid produces the aest yields.
la their short discussion of the rseehaniera they repeat the proposal of 1/allach, while suggesting the following as a possibility*
m*c (oh) nsro-esss %o
93i resulting icine is tken reduced "by foraic acid.
At ahout the same tiae, Boevre pad Courtols^ suggested that the initial step in the reaction was the addition of f onaaMde to the carhoayl grotto,
ISCO 4- HgBOSO ~ M*C (OS) WXffit
vnile Pcrie and ttogers20 thought that hoth of the proposed ncehaaisns
iaight tie operative. .
In l$'f6t Bhivo aM Siiive^* reported tliat at roe teranerature forranide adds to pyruvic acid to give cwhydrosy a-fomcnido propionic acid. "Upon dehydration,a-forfilMdo propionic acid urn ohtslaedi

They t?ore til to isolate "both of these cojapoissds in fair yields. Shis reaction, they stated, shows that the addition of foresaid* to the earhenyl group is the first step in the Leuefeart reaction.
5he nest attemt to clarify the mechanism of the reaction t*as nade "by /HmsaOMT and ItUdgsa.*2 She et^ect of their writ vast to determine if there were conditions such that the reaction could he carried out with ajxsoaitsa f onaate hat not with forms&dde.
hey found that uhen eaotophenon is heated with fonsaoid* in diethylene elyeol solution at 120-130, no reaction occurred von after as long as fifteen hours, while & yi3ft of 10 per cent was obtained with emoniua foimte and acetophenone after four hours,
In order to explain the fact that forrasjdds is a satisfactory roceoat at higher temperatures, they proposed that the following cuilihriun operates at tewaeiatures ahove 155*
and that the enwmiua f ornate tfexs produced is the material wMeh enters into the lieuctert reaction.
fhey alee found that the rddition of anhydrous caleiuB sulfate to a nixture of formedde and acetophenone reacting at 165~l?0e levered the yield from 30 to 17 per cent* They regard this fact as proof of the e^lioriua proposed above.
On the "basis of this work, they state that ataaontet fornate is the required reaetcat sad that the meeliaaisja proposed hy Wallaeh is correct*

Mmnt lsltaaeously tilth the proposal of Aieimader end l&ldiaan can the .work of tvebers sad B*ttes)33 hey feund that when forjracdde te used as the rcaetont, acid catalysts increase the yield markedly. In direct contrast to the work discussed ahovo, they propose that the repaired reactaht is fomaaide and that the function of the acid catelyst is to increase the pelrj?ity of the carhonyl ipraop, fhey suggest the following as the first step of the Lmtchart reactions
jmco + ir? m*tm ... . i 2 i
During the following year, Bennett cad Ifertes2^ found that add catalysts increase the yield of tertiary siaines prepared frea substituted fors^sides and hetones.
Indicative of the confusion on this subject is the fact that in his recently published hook Alexsader2^ repeats that aramiem formate is the recMred roactaat end that, the correct jseehaaisa is that original 3y proposed "by Wallach. He does not mention any other j^nsihllity. lloore in his recent review of the I.euclaart reaction, discusses hoth of the proposed T&ohanisxis hut does not reach a definite conclusion as to which is correct.

Chapter XX
a coupjsrisoh of she tmcKsm miasms
A study of the literature on the Leocfeort reaction reveals several factors tMeh east he considered in any eetirieen of tho efficiency of the various reagents anion Eey "be used.
Ohvieusly, the temperature at which a reaction is carried out affects the reaetlem treesesdouslys it snust $tapeffo* he carefully controlled.
Some workers have removed water froa the aisturo during the course of the reaction, while others either hsare not dene so or have net reported the fact* It seems clear that the removal of water increases the yield t&en csr/ rep^eat'otlier than fowaaiaid is used, ft is not clear, however, whether the presence of water decreases tfe yield hee&uso it causes the reaction tesg>eratops to he lower or "because it is itself involved in the reaction.
In an effort to determine the role of the water, the runs recorded in Sahle X were carried cut. Ehese data show that water is involved la the reaction. As sore and taere water is removed, temperature rises; cut yields are decreased if an acwunt of water approaching the theoretical ejaaaiity is rew#4

isfsof of m& mmm* m ksbjr otott e&actioit smiMR2i akd
Four Jfoles of ^woaitss Formate nnd On Itele of Aeetopheacne
Idmiia Hcssoved Cm.) fist (Hrs.) ^esa^ratssps- BOM 135 16
Ihl to
5 h m
72 h %5f
A eesp*isea of the efficiency of the- various reagents is ; shorn la 2able IX. Shis series of reactions was earried cat without tli renewal of water at 135. m Mh*at te^erature a% atmospheric pressure at i&iejb. such a cta^arisoa could as tsafia.
a mwmmm m vmsmmm 135^
Ifeles per Mole of Acetepheaons
MBBtxB&xB& forssate Bolts) .*.........*. .....16*
MmMm format* (2 mles) aad Foraacdd (0 moles). ...... 2S
Foraaaalde (2 aoles) and Stan&e acid (2 laoles).........ZL
Sbn^sside (fy noles). #.*....#. .......

Sefore cay m&iax&m can he proposed for the reaction, on other ooures of confusion mst h removed* 991 contention of Als-sand** r that araniu fornate Is the recuirod reaetaat cannot readily a# reconciled with the other e^erlmental data which liars hesa reperttd* therefore # it was decided to attest some low te^mtort runs with scetophejisii sad foresaids*
A cojaarisea of several of the Leuelsrt reagents at low te^>eratares# with, m& without oolveats, is sham in fa'hle III. Hbte that although the yields obtained with f ormsside or low, they are real.
Boa|5ont Solvent & : ?>>
Aeetophonoae (l mole) plust WovmASm {k moles) 135 k
l&rsetsldo (h moles) Bensene 30 115 21
Ingersoll* (fy salts) -BHMM 113 25
foHRsmtds (Alleles) isntSormlo aolddlsdlal Sutanol m 5
Ifermsmifi* soles) Bcttyl fornate 131 ?
^>rid*(%Belea) and Sbrsie aeia(fyle) Putjdfomate > 123 13
W&mMM (h moles) 155' 8
aHlSnnaa* teageatt later is distilled from a latere'of 210'id. of formic acid ad 215 6. of eoj^reial atpsaltaa carhoaate mtll the pet tss>erature reaches 165. She resulting ala&ave is used as the re-ageat.

Ife reason can ho advanced ty the author for the failure of Alexander to ohtain a yield when using foresaids at low- tecperatares* However, it should he noted that while he carried out the reaction in dioSr/leais glycol at 13O0, the present work was concerned with the reaction in various solvents at their holling points, ^rthsriaore, when an alcohol was the solvent, a portion of the formaaidc was removed from the reaction du to the formation of a formate ester of the alcohol, further investigation may show ite$ter this fact is significant.

fibapter Xtl
a samsss A essvful study of the litemture and of the wrk which has Just soon outlined yields a nuitoer of fasts concerning ie reaction. Shey can he host svaaarised as follows t
1. Mien water is. removed, a mixture, of foasasside and foraie acid elves the osot yields
2. /OTwaiua formate gives hotter yields than formamide, although. It does not give yields as high as formic aold and formsmido combined*
3. A mixture of formssaide and taaeenium formate is as good as, hut no hotter than, mmtttixm formate- alone.
tp At %m -teeperaturos tdien water is not rosaoved a mixture of ftaonium formate and, fonxstlde seems to ho best,
5. ^Ith oay reagent other than foresaid, yields arc itiproved .tihea water is removed from the reaction mdjEtws*
6. !The yield is lowered %3hes a dehydratiae agent is used alosg vlth fessaamide.
7. Secondary and tertiary amines may "he prepared "bp use of substituted formamides,
8. Acid catalysts increase the yield *.iho formamide is used as the reagent.
$, A reducing; agent is rae^rod.

It wilt he ettserved that in every ease t&xmssAM Is initially present or can easily he formed oy dehydration of mmx&m format*, that mime cost he somehow concerned in the reaction,, and thai, a reducing agent is required. StavJSttinvt, the familiar resonanoo forms of the ketone KR*CO BR*

OhaptOT f?
On the "basis of the preceding sumary, it is peesilde to propose s general aechsaisit for the Icaidmrt reaction tMeh accounts for all the facts* Ste following i^haaista Is proposed!
or |it
m*~o" rt^m mI|^io - HR^eanBcuo CD
J.% the tefiperatare of the reaction Cia^5 or hi$*er) water
Splits OUtf
01 H
B&tflnQBD M0=sS 025' <* (2)
fh predstot of step 2, haviag conjugated aystoia of tm
fieuol "bonis, should have the following rosoaimee fotinftt
f + *
im0ss If- Css 0 SKt0.~ ITS C 0
13 water obtained in step 2 then hy^rolys^s som ferassl&t to ^ive a snail concentration of eistaottluB f ornate tJhieh can serve as the reducing stnt heh the reaction requires. She Introduction* of & dahydrating agent moM decrease the essenat of mmntotSL formto lAich could he fenaedi therefore, tho yield of the reduced product would he di4niohed

* I ?
?j**c is c~ cr # "o ess o *
L "koo
** CmtHa-^siwcTJ coa
She final step is accoi^lished whtn the msmdm im gfcv** \sp a proton to the intermediate *Mch tras formed la step *M
f ?
Che' nc-iir c- o"] + -* mm'c-iazz e- oh +
- HE* BO SBPSE30 (5)
In this ease steps h and 5 Halt the reaction, sine* the con-
centration of the reducing cgent is very small.
1% will be recalled that Alexander and mi8is&^ reported thr.t the addition of anhydrous calcium smlfate to a reaction mixture containing paMdi&Bm and acetophenone decreased the yield from 50 to 17' per coat..
In a eolation containing fonaaaide >Jiiea has a very higa dielectric constant^ ..enftldMtt- formate io pretJaMy M^tly ionised. She most reasonable aee&aalsm for the redaction "by the format* ion consists of the addition of the formate ion to the positive center of the formte&de compound, followed by a hydride ion shift with ths subsecuoat release of carbon dioxide*

tell.* 'mmm imatite-a&fmte Mm
Yields are increased yfhm formic acid is aMod -to a reaction, mixture obtaining ths Intone and ferissaido. 5Ms can he easily accounted for on the "basis of ths- proposed -mechanism.
Steps 1# 2, and 3 arc essentially tissehsagod, elt&mtft formic acid proMoly iaeroases the enol form of the Iseteae. Siaeo fowl acid is present, the concentration of the effective wt&ustoag sypst is mad* hl#ier than in Case 1* therefore t steps k and 5 proced more rapidly and the yield Is thereby improved.
Pais |pL leactan^t 1foap^umi ItaMBti
isaonitim formate gives hotter yields than formaalde*- Shis is eas^lained as- follows*
Upon heatlog, csamnium formto is easily -dehydtatod to forma* ml&a* tffce fora^ddo thus produced adds to the fastens, and.the re--action proceeds Just as in Sase Jig>ie csmoniura format is present to serve as a reducing agent*
Water mast ho- removed in order- to insure good yields then any reagent other than mm$M- is used* ffhara are ohvlously tuo reasons for this* first of all, the *mo9& of water facilitates the formation of formnlde from the mmolm formate as oll as tho formation, of the intermediate of step 2, SWthermor*, the presence of a largo ffentity of water -feeofs the toapomtars cospa*$ti^ low. Hote, howmr, that according to the data of fable I, it i'

mtAm to remove toe much vater. hn this Is done., substantiality alt the maaofam formate has been converted to f fttvorit&ft at the jpemse of the reducing agent, and yields are- decreased.
T&ten tiater is removed, missed fo^rmsmtdo ammaium formate is as good as ataanium formate- lone but no cotter. Wmmm?* when no water is removed, the cisture is hotter than smsKraino formate salons.
fhe same'general mechanism fits the behavior of the reaction mixture when both foreamide and asaaonium formate are present. Seme i#ter;.is removed in, order to force stop 2 forced, since this water is not used up in the formation of a reducing agent. In this case only a small aaount of water should he resaoved, much less than when eiaaoaium formate alone is present*
tthea no water ic removed, as vm the ease with the data of ffaoio II, the tslxftn** is better tta ammonium formate .alone-, because the concentration of formamide is sraaoh highor.
Shis general mechanism, thoreferi* seems to fit all the facts concerning all the possible roaotaats used in the Ijeaefeari reaction.

Chapter ?
la order to investigate a Dechanism it is aeteasaiy to determine tee order of the reaction, which represents the number of couceatration factors appearing In the equation for the rate, the obvious method of accompliahins this it to vary, the concentrations -of the possible re-aotants and. to determine the effect of these changes. Integrated aauations based upon various orders are applied to th* data until cne Is found to fit.
It should act be necessary to devote space here to the derivation of the various rate equations. A list of the integrated forms together with the simple methods for determining if the data fit should be sufficient.
First Order* 4 * frodue^e
. <-*3*** m &t/2.33 * u nfeere jg, is the concentration at any time, & and a constant of integration. A straight line is obtained when log & is plotted against tine.
*J * cj 1/0 *i*
whore c le tee initial concentration, e, is the concentration at any time, 1; and , nnothor constant of integration. A straight lino is obtained %&en %.f jp. is plotted egaSaet time.

e? > e| -1- in Hg^L s fct
where & and $< are- initial concentrations, cad & Is tho emount re>
acted in Urn, A straight line is obtained '..hen log ^'^^.y is plotted against ties.
tJaforlarastely the leaefeart reaction, as it is normally carried at, docs not lend itself to kinetic investigations. On of the basic conditions of fee kinetic theory of solutions is that the sssdiua in !ileh the reaction occurs mmt be reasonably constant. Since in xsost cases the Louokart reaction is carried out t&thout a solvent,, the- conceatratioas are very Mga cad the ediua changes constantly as tho reaction proceeds.
rurtheraere, tAtea the roactaats present are only a ketone and formasAde or amsniua formte, no reliable rathod for determining concentrations is available. 5ho only oao possible in this case, tho measurement of carbon diosd.de evolved, is unsuitable because part of the carbon dioxide is trapped in tho condenser in the form of amta&m
Shoo, it scons that only the reaction between formalde, formic acid, and a ketone can be adapted to a kinetic study, since ta Mils case no amaonia can be evolved.
In order to doteraiiio the order of the tlvtt etep of the action, it is necessary to avoid the possibility of the reduction step being the rate-deteraining one. fhis nay be most easily accomplished by tho employment of formic acid as tho solvent. Under these

eooaitiens tho acid concentration is saeh greater than that of the other reactrtnts; the reduction step should occur is&eh more rapidly than tho initial step*
Several preliminary runs were carried out in order to tle-temaina the most practical conditions for kinetic measurements. It was found that eosipar.tively low tei^ratures and high concentrations -are required, tfhaa water is not resoved, the reflux temperature of the reaction nixtare decreases as the reaction proceeds. It is therefore necessary to carry out tho reaction at a temperature below tho reflux temperature of the oisture at the eetgg>letiea of tho re- -Mtfcm. It ^ moma to vmf to**** At this tesperature solutions in which both formamide and acstophenone wore 2 molar resulted in reaction rates which were much too slow to "oo practical. Even with concentrations of 3 molar, tho reaction would he one-half complete only af tor about 336 hearse,
fhe rate constants sMch have boon obtained are coE&lled in fable IT* fiie data collected during the vcricus runs are listed in fables V throu^i IX? the deteminatioas of reaction order are shorn in S'icures 1 and 2* ,
Saaaination of Figures 1 end 2 reveals that tho reaction under these conditions is most certainly second order* Very excellent straight lines were obtained i&m the proper identities for a second order reaction were plotted.
ffhc data which are compiled in fable IV, however, show that the values for the rate constant do not check very well. Hots that

19 Figure 1
KHKTICS OF tm IEU02AB2! jRBACTIOI Solvent 90$ Formic Acid
A, B k M Aeetophenone and Foraamlde 0 "3 E Aeetophenone and Formamide
/ '
/ o
V/ p**te_,.,:...........;,i...... ......_______.__,j__
0 20 w> 60 80
Time (hoars)

A 2 M Aeetophenone, 4 J| Formamide B k g Aeetophenone, 2 g Formamide
o.oi r
lime (hours)
Figaro 2
[HS2ICS OF tm LSUCKAE3? BEACTXOH Solvent 90$ Formic Acid

t'awb ffi
jlcetopheiioise- aad SbsnM&sVSa 9^ foraie Mid
Initial Concentration to Moles per lAter Sate -Constant (Moles per liter-Hoar)
ft 2*ft x ItT3
ft ft 2*2 x 1 2 ft 1.5 ae XCT3
ft 2 1*3 s ir3
3 3 1.1 % l It rust he concluded, therefore,, that the oaeentratloas used in these determinations are too high; the re^i&iremeat that the r@-action medium he unchanged during the course of a determination hat not "been mot*
It will ho recalled that It was proposed that the first step in the Iieuokart' reaction consists of the 'addition of formamid to the. .ketone* $hen this is t&e rate detaining step,-as it should he under th conditions outlined above, the reaction'should indeed b second order*
She fact that the kinetic- study discussed above shows title to be true constitutes excellent support for this- step of the psapowA
the value is fairly constant when the total t^aceatratlon of re&etants it 6 molar,, hat that the rain obtained whan both amide- and feetoae are h molar does aot cheek with the other three*

ntmwB w mi immm rmmm
ft H Acotophenono, ft QTemsmtem in 90$ Pornie Aeid. $ex&s^t^&l2ft-5*
fiise (ITS.) Carson Dioxide Bsrolved (Hole*/liter) Oeaeeatration (Holes /Liter) Ketone end Add 0
0 ..... 3.85ft 0.259ft
1.00 3.810 .2625
2.00 0.08? 3.?56
ft.00 0.15ft 3.700 .2703
.00 0.22ft 3.^30 -3755
900 0*321 3.533 2830
12.00 0.ftl8 3.ft3&* .2910
22.00 0.675 ; 3.179. 31ft5
Sft.OO 0.9ft0 2.91ft 3*31
36.00 0.993 2.861
ft?. 00 1.182 2.572 37fta.
51.00 1.255 2.589 .3850
5&0Q L3ft5 2.509 .3986
61.00 l.ft2ft 2.ft30 .ftH5
72.00 1.55? 2.28? *ft37i
80,00 1.572 2.182 .ft583
Sft.OO 1.730 2.12ft .ft707
9S.00 1.850 ......,.................. .,.., ,,, 1.99ft 5015

21139 (Hrs,) Careen Maxi&m Shelved (ttoleo / liter) Concentration, (Ibleg/litcr) Ketone and Aside 1 f
0 ...... 3-990 0.2505
1.00 0.02ft 3.955 .2ft21
2.00 .0(52 3.928 .25ft3
13.00 .ftlO 3.580 .2793
21.00 .522 3.368 .2960
26.00 .7**8 3.2ft2 .3085
37.00 .973 3.01? 3315
%mmtm' of j&mm suraon
2 & Acetophenono, ft M Pornardde in 9$ Ferule Aeld. Tos^eratures 125
fiiae (Hrs.) Caroon Eiea&de Evolved les/liter) Concentration (Moles/liter) 1>ta~2&
Ketone Aralde
0 # 1.93ft 3.91ft 0.00000
1.00 0.012 1.902 3*902 OOlftO
5.25 055 1.859 '.. 3.859; .00651
lft.00 .lft6 1.758 3.768 .01795
17.00 .182 1.732 3.732 .02271
22.00 *230 1.68ft 3.58ft .02928
25.75 273 1.5ftl 3.^1 035ft3
35.00 iM 1.555 3.566
radios os? tm tMumm mmim
ft & AeBtopbaaoaa, ft jK faroasaA la 0$ Feaaic Acid, temperature* 125

mamas of mm rammm mimim
ft | AettpJimae, 2 K ferxassid la 9C$ fossae Acid. fej^eraturanlEjf*
(ffifs.) Carbon Dioxide Jfrelved (Moles/liter) Concentration (ISeles/liter) b (a x) a\oay
Ketone Aisld;
o 3*983 1.983 0.00000
2.00 0.021 3.962 .0023s
ft.OO .^0 3.9ft3 1.9ft3 .00W7
8.00 .075 3.908 1.908 .008W
12.00 .lift 3.8# 1.8^ .01310
2ft.0 .219 3*?6ft 1.76ft .02626
30.00 263 3*720 1.720 .03212

Sins Carhon Bieasld Solved Concentration 1
(Srs.) CUsles/lltor}. Ketone and Anddc C
0 ..... 2.993 0*33^
2.00 0.013 2.980 .3356
4.0ft' .031 2.962 .3376
7.00 059 2,93* 3*107
10.00 .088 2.905 .3**42
14.00 .12? 2.866-
22.?5 .206 2.787 .3588
27.25 .24? 2.7*6 .3641
34.00 .299 2.694 .3710
38.75 335 2.658 3?a
-Obviously, the Mnetie studies Just outlined an t>e of value only for the clarification of the first step of the reaction, fhere does not mmm to he a practical method for investtg^ttsg the regaining steps from the standpoint of .Mnetie studies.
It now hecoms necessary to advance sone proof of the presence of an iaterrsediato of tho type ft*lCrsH0HO.
mm t%
IIS1E22ICS Off ws BSftCflOl
3 J Aaetepheaone, 3 M Soriaaiild in 90$ rona&e Acid. SoEpsraturas 125

In recent years, ultra-violet absorption spectroscopy has proved valutMe for the detesinatin of eoi^ouaas of Ixmm or un-lasom structure, since tho absorption of ultra-violet li^it is de~ teradaed by the electronic etruoture of the mlecule.
The absorption spectrum of a substance is the speetrun obtained %fhen the absorbent, or a solution of it in a suitable transparent sol-, vent, is placed in the path of tho li^ht emitted by sojse source, the spectrum is obtained by means of Eseasuremeat of the pfogortiies of ll^it vhlen is absorbed, SMs is accots>lished in modern instrussats by the nm of a photoelectric cell bich is capable of cBsriag Use intensity of a beos of light vhien has passed throng* tho pare solvent with that which has passed throu$i the solution under investigation.
fh intensity of absorption is related to the thlcleoees of Hie absorbing layer and tho concentration of the absorption by the familiar 3eer*!*a8bert lew, which states that the fraction of incident light absorbed is proportional to the number of absorbent solecttles in the light path.
therefore, log I0/Iss 0.4343 ecd, %imm l& Is the incident light and I is the transmitted light at any one mve length, Jj, is the concentration of the solution in noles per liter en& j^is the thiols* ness throu#i ^hich the ligfrt Is transmitted, c, is the taelar extinction coefficient of the solute for tho particular wave length.
She curve relating wave-length and absorption intensity is characteristic of a substance. Since the vpIuos of the extinction coefficient are often large, it Is eustoisary to plot log & insteal of & itself.

This l\v&mmtsl interpretation of uXts&?iolet absorption qgeckm of nay tat tho sts^Xoftt of Xeale i estrcsoty mw^lm* ti&mrcx, it is possii&e to Seises tho gonorel nstare of a 1cc0,# $y jaess* of m&ivtesl corarelations eotveea i^sorf tlom pectm m& structure*
Cossjletsay satoratefi ali^hatits coi^rsouafto aosor'b only in tho fur ult2a-.iriea.oi region of the outsat*, tAdl csspote^t containing a single tisatttrai#& gr% shotr M^intenoity atmorption in the XfO-200 txja ro^ioa. I^thylone cua& earljonyl isroaps also chow Xow-intonsity "bands in the twi#%orno& af 8^**
\fbm two or tr eJiroisapaorea re present in tJjo sane sole* their flubaoarptton is usually c4&itlf ss Ions .as they art eep&r-etoS "by two or mm single "bonds.
*hm eliroxaophores is conjugation, hnvovor, ehw a new tyoe of absorption. 'She absorption ruadnan due to one of the flrotipe is greatly intensified oM shifted toward tfce visible region of the ispeetresf cad at the sese ttae# a new Ktoadteaa is produteet. for esas^lo, cro-tenaMeiiya eafeiMts jsaztea at '&f nj& aad 321 a ^a, %M1 ethylene sat seetal&el^iie lotfe asMMt o SaUi asatesii at X85~l$0 mfou
Sherefore,, it should not fce diffienlt to their the presence of s eoaperoa eaataJaSstg a oon^iito eysten in,the prsseoal-^f xttbm m&jmm&u tAddk contain only ono douol 'feond.
lots thai in tho ease of a sli^la sliphatie feotane, of fora&e add, cM of the 8J38titssfee& forinaai&e, the final protest of tho reaction, only on doo&l oonft is present, fhe proposed in&enssfil&t*,

howrer, contains a conjugate system of two double bonds. Vor this reason, the cbsorption carve of the reaction nixture after reaction has occurred should he mrtoedly c-wnged from that of a sixtare of the roactcnts end products.
Preliminary delNKsaJSations of the absorption curve of the reaction nisture of acotophenone and foraardde indicated that the use of this mixture is inadvisable. Acetopheaose has such intense absorption vsaSm that the abiorptioa oaxlisa of a compound la low concentration wuld be coj^letely obscured, if they should be close to those of acotophenone.
In order to avoid such interference, tttleh is due to the resonance of the hengene ring, it wae decided to use sethyl isobutyi feetono instead of acetophenoao v&en tho ultraviolet absorption curves verc to be determined.
fhe absorption curves of fon^asdde, usothyl isobutyi hctone, ant 2-mcttiyl-4-forrsacsidopentane, the final product of the reaction, are shorn in Pigore % Ifet that the %m asides do not shot* an ah sorption nroeteua' above 220 mfs.9 vhile rthyl isobutyi Iretone has a faaxlraaa at 2) n jx*
Figure* ft and 5 depict typical absorption curves of the leuckrtrt reaction laixtares after reaction has occurred.
Ttm reaction nirture represented by the curve of W@pm ft
contained forccaaide, fonaie acid, and rwthyl isohutyl ketone, the
reaction was continued until most of the ketone had been depleted, Sets the appearance of a new ftaxtesa at 3*fG mj& and a new shoulder uhieh represents a mm&mm at about 2ft0 js/a,

3 t
A formaai&e
B 2-He thyl-W oraani do pent an o 0 Methyl isobutyl ketone
Solvent t Ethanol
\ 0
1 I
280 300
Wave Length (m

Pigurs V
280 300
Wave Length (ra/i*)

Carre A, Figure 5. obtained from a reaction in which only fonaatald and the ketone were present, Ho to that in this case, the mx&mn at 340 s^t is almost completely obscured by the absorption of the he tone,
flie reaction mixture vhich furnished Carve- B, Figaro 5, also contained fomaalde md the Ice tone; and in addition, a small actount of aahydrens calcium sulfate was present. In this ease the shoulder at 340 a/at is rrouch raorc pronounced.
If those new absorption isaxtea are due to the presence of a fomtoido coapounft, tte presence of a dehydrating agent wold be ex* Ptcted to cause its absorption to- be tJere intense. Since the addition of onhydrous calciua sulfate does indeed cause a more intense absorption at 240 and 340 sya, end since these nei? jaasdbaa cannot be attributed to the startingsatoriels or products, it ooeas entirely reasonable to conclude tint an intemediate of the type M'CsB CSO is indeed fomod during the coarse of tho ^Jdsart reaction.
It is advisable, wherever possible, to essploy more than one method far1 the identification of a reaction intermediate, particularly tahea that intermediate has not been isolated, fherefore, it vm decided to carry out a polarograpMe study of a Skaids&rt reaction nixture.
She poltregrephie method in genosal my be defined as an aaalysis based upon tlie electrolysis of a very minute fraction of a solution in a cell tnsie!iag of one siaall, easily polerisable, and one large, non-polarisable, electrode.2? flic polarogrsph is m iastroiaent vhich records reduction currents resulting fron the applicsfttai

2 I
[ I
figure 5
4 r \\ \
! V
240 280 320 360 400 440

of esfioally increasing eathodle potentials to a drepplsg;:jwmy electrod*.2^
fltea-a potential is applied seres a cell containing a solution of an ionic substance, the very faaili&r Ohms leu, Br X8, cpplies. Sines the resistance of the solution is constant, as the potential is increased the current increases proportionately, until the potential Recesses high enou^i to cause the reduction of som suastaac In the solution. %en this occurs, the snount of current eonsumd increases rapidly. -
How, fcSien -fee electrode is very swell, as in the case- of the dropping nereury electrode, and %ftien the solution is not stirred, the solution around the surface of the electrode Iseeoms depleted in reducible mterinl. fMs phenomenon Is known as concentration polarisation, ifliea tf-ie potential hecostes- large enough so that all the reducible suostanc which can get to the surface of the electrode during the drop tire is reduced, cesplete concentration polarisation has "been atstained*
JLt this point, the current can no longer inere&as, "because It is detenained "by the rate of diffusion of reducible aaterial froa the bulk of the solution. Since tne rate of diffusion is proportional to the difference in concentration in the two regions "between whieh the diffusion occurs, the diffusion current is proportional to the concentration of reducible ions in tie "bulk of the solution.
tBberefore, it has "been'established that the potential at iMcn'
reduction occurs is characteristic of the mihstanee, hlie'the Mttmim current at this point is proportional to its concentration*

nariber \A\it&i are oxidiuable, give charactoristie fOlarogrsphie waves.
Included saaong the reducible substances are oxygen, carbon dioxide, unsaturated organic corsoounis, srf, soas t?ldehyftes and ketonesj while carbon conoxide, alcohols, esters, and other aldehydes end ketones are not reducible.
(Therefore, it appears that a compound nuch as the proposed intermediate should be detectable by neans of its polrrographie reduction wave. In order to avoid any possible interference due to the bensene ring, m^byl Isobutyi ketone -was used insta-ad of acete-phenone,
ffha first step in rn attempt to shot? the presence of a new substance mat be, of course, the establlshaent of tho pol&rogrep&ic wsares of the material hnowa to be present in tho reaction mixture.
Figure 6 show tlie results obtained **xea an attest vm aade to reduce nothyl isobutyi ketone* txsins a solution of lithltaa chloride as the supporting electrolyte. Observe that no redaction of the fee-tone lias occurred. She low waves which are present can only be due to a snail 'smart of dissolved ojsygen or a snail smms.% of organic
>J3 oft
peroxide dissolved, in the totoae. *
Since lithium ehloriefc itself is reduced at sibout -2.2 volts,
it can only be used as the supporting electrolyte for Materials which
are reduced at lower potentials. Therefore, the deterainations upon the Ijeuefesrt reaction mixtures wore ade -with tetraaethyl mmnlxm
broai&e as the supporting electrolyte. Using this solution it is possible to operate up to a potential of -2.5 volts.
a large mmbor of substances, "both inorganic and organic, which are reducible at tluj droi^lngH^reury electrode, and a smaller

A 0.1 u Lithium Chloride
10 r
5 r
o u o
o i^-
B 0.1 M Methyl isooutyl ketone in 0.1 H Lithium chloride

Vigor* 7-A is the polaregma of a 0.1 M solution of the support-ins electrolyte; 7-B is the polcregraa obtained after the solution had been rasde 0.1 | in methyl Isobutyi ketone. Obviously, tho ketone has not been reduced.
However, the polarogrris of a 1 per cent solution of tlie reaction mixture, figure 7-0, shows that reducible material is present in the solution. It is thought that the ill-defined waves between
-1.7 cad -1.9, at -2.1, cad at -2.25 wits are due to the peculiar
behavior eAibited by aqueous solutions of forssside. However, the ware at -2.33 volts is not characteristic of fonaaiadde, and rust be due to soaae new substance.
A ccqplo of the revet ion sisture woe then washed several tiiae* with water in order to remove all the f orasteld., f be water*. ;' insoluble rsaterial was then subjected to polarogrejplde reduction.
figure- 7- is the polrrograa of a I per- cent solution of. this rdzture. Observe that the waves due to tlie foresaid* hsve disappeared, while tho wave at -2.33 volts is jssore clearly defined, Tnevefore, it seesss reasonable to state that. an interjaediate of. some type is present cad that its polarographic reduction ware occurs at -2.33 volts.
Most siiaple unsaturated coi^ounds are reduced at notch lower potentials than this. However, when tlie cormound contains a resonating systea, tlie reduction becomes mere difficult. She mre intensive the resonance, the sore difficult is the reduction, for eaaasple, the reduction of rllyl alcohol lias been shewn to occur at
-1.6 volte, while phjtol t!ie chlorophylls are reduced at about -1.9 veits.32

Figure 7
20 {-
1 0
Potential (volts)

Since the resonance of tlx proposed foratei&o cesa^ounk,
M0a:HSOt is proTsably atm rare intensive, it is not at all unreasona'bl that its reduction trave should occur at ~33 wits.

Chapter VI
She acetophenane, nethyl ieoliutyl ketone, end fornaaide used la this research t?ero 0. 1*. chcnalcals, carefully dried and redistilled "before use. "The forado acid used was comseroial per cent forsalc acid.
, She eosparatitre runs listed in Ssoles I end' HI wore .carried out at a temperature such, that a eentl reflux was Maintained, She runs compiled in fable II wore maintained at constant temperature by Beans of a Brown indicating controller.
She product of all runs of the ieuekart reaction listed in this work was isolated according to the following general cethodt
"The reaction mixture wns allowed to cool and was trashed three tizass with water. In order to speed up the separation of layers, 50 lal. of hensene was added to the nixture. After separating as mda water as possible, the bonsono leyer was subjected to aseetropie distillation, with, separation and renoval of the lower layer of the distillate, in order to dry the material thorou^ily.
She resulting dry sr.ixtu.ro was then distilled through a snail colum capable of effecting; a separation ooulvalont to a*bout six theoretical plates. 5?ho fraction boiling at 138-141* at 2 jss. pressure was collected end reported as t3\e yield of a-phenylot3r/l forsiaaide.

She Mastics jasesurenents were obtained as follows! She starting materials were- weighed to the nearest Eilligrr, sade up to 100 til, with foraic acid ad placed in tlie reaction flask. Shis flask was fitted with a reflux condenser attached to en absorption train consisting of two traps containing concentrated sulfuric acid and one containing anhydrous calcium chloride. She entire oyster* vas swept by a streasa of nitrogen whicli had been first passed through sizlfuric acid and a tube- containing Ascarite.
She scount of carbon dioxide evolved was determined by passing the effluent gases through tubes containing Ascarite. She weight of carbon dioj&de trapped in a measured period of tirw was then do-tewaiaed by the change in the weight of the absorbing mterial*
It was found inmeeesisajy and undesirable to sweep nitrogen through the systcsa continuously, sines an appreciable aoount of foBiie acid was pidasd up by the erorront of nitrogen, therefore, the systea was swept out with nitrogen for ten minutes ^ust before a #a^>le was to be weighed. Shis sweeping time was found to be sufficient to carry the carbon dioxide into the weighing tube.
&\,im$m of Menk runs showed that a blank of five milii-graiaa had to be subtracted f roa the apparent weight of carbon
She use of carbon dioxide laesoureasata to follow tlie course of the reaction is baaed upon tlie general''equation for tho kcuekart reaction*
HS'OO Hg&CHO HC00E * JOfiCBOBlim + KgO + C02

For every mle of carton dioxide produced, one role of Intone end one ole of foresaids is consused. On this "basis, it is quite circle to calculate mi&*-ed ketone concentrations itm the atsount ,of earl& dlosAdsr evolved. -
Ultraviolet aosorptlon curves were olbteined "by mens of a Seckaan fcSedel w (Starts &petrophotor^tr. All solutions were originally diluted to a concentration of 10 per cent, end further dilutions were ftade, as necessary, in steps of one-tenth. In Best cases j solutions of 10, 1.0, 0,1, end 0.01 per cent were requir-ed for the corsplote absorption curve. She value of tog; Ie/1 was read directly fros the instrument. A raedlfled extinction coefficient was then obtained "by dividing tliis value by the concentration of solution being measured. Thus, the values plotted in "%WI 3.
end 5 were obtained f rem the equatioat
log 10 / I
log & r log . ... .i
Headings were talflen at 2 nfx intervals at critical points on the curve and at $ mp* intervals over the reiipiiilag range. '
All polerogrnna were m&m with a S&rgont^eyrovsky Model til recording polarograph. "The tutorials used to make up the solutions of supporting electrolyte were analytical reagent grade eheraieels recrystollised several ttees. "Ebeee solutions were made in a 5/pr cent water-ethanol mixture, in o?der to insure complete solution of tho ketone.
All teaperaturos reported in this work refer to the Centl-grade sold* -

Chapter Til
sauKA&r aw oohcsusiohs
A eaglets mechanism for the Xeuekart reaction hae been proposed.
It has been shown that this nechanisn fits all tie published mterial, with the exception of part of the work of Alex?nder which has been shown to be in error.
Consmratlve runs with various lisuekart reagents have been carried out, and the results obtained correlated with tho proposed faeehaalss.
three separate attacks have been made upon tho problem of proving the rtechanlem to be a true picture of vhr.t actually occurs in the course of the Lettekart reaction.
It hae boon shown, by mem of klnetie studies, that-the first step of the reaction is second order, which is to be expected .if the proposed raechenism is correct.
It has been shown, by ttosas of spectrophotonotric studies and t3ol: rographic studies,- that an intermediate such as Is proposed as a part of the i&eha&isn is produced in the eourso of the Leucltart reaction*
It mst ho pointed out here that none of this raterlal can b regarded as conclusive proof of the eeehaaiso. Howevnr, the fact that all known data, both that of the literature and that resulting froa this work, support the mechanism in' every detail constitutes strong evidence of its validity.

1. leuefcarfc, "fly.** SH 23**1 ClB85)
2. Loiuifeart'eiia Baeh, Ber... 2128 (1886").
3. lerwkart cad Bach, Bor,. 20,, 10& (180?). .taucfcurt end Janssen, Bcr. 22,, 1^09 (1889).
5. Leitekart cad tenpo, 'for. 2J,, 1851 (1889).
5, Leoefesrt, . Txwfct. Chan, > ^ 330 (1890).
7. Wallach. 21. 3992 (1891).
8. ifellctdh end C-s&epenfcarl. Ana,.. 269, (1892).
9. Uallach, Arm., 100 (1893).
10. Vailaoh, Ann., 296 (1893).
11. tfallaeh, An&., 2j&, 338 (189$.
12. Vallach, Ann,., 200,, 283 (1893).
13. IvallatiOv, Sattimr, and Altfburg, Ann.. 3fr3. 5** (1905).
lft* KJJner, . Jhica. Phys. Shea. Sac., 22L 1*3599. 2IU 381 (1900)I T. Cho. Soc. (Ahs.), 22,(0. 277. 333* 629 (1900)
15. Ingersoll* at 1., JT. Aj^. C|ie^.. See,, ^8, 1808 (193$)*
16. Hooro, "Organic Reactions," Vol. Y, Wiley & Sons, I9J19.
17. Bove311, J. A&. Chcm. Soc. > 520 (1939).
18. Croeeley and Ifooro, ..'.G|g, Chen.. 2, 529 (19*<4)
19. Iteewe and Cotirtois, Boll, soc ohla., 11, 5^5 -.(19^)
20. Davies cad Eogers, J. Chen. Soc., 126 &9#j-).
21. iliive and Oldvo, , Airu Chen. Soc., 117 (19**6)
22. Alexander and l&ldBsn, .. Chew. Sec.. 70.1187 (19^)*

Betmott caa HrA*, . Qypu Esq., 2U 355? CW).
25- /Aescmlo2*f SJPi*iftsljilcs of Ionic Orgsaie' Ii^ians,R tfiloy & Sons, Ife? Tarts, 1950,
27. iktllcr. Chop, aaaestlon, Id, (>5, 111 <19^l).
28. ?m i^saollrifxsf IlaGas, Cjwep. tSlite-jt, tta 1Msfcsy# Cjorflffion..
. 105 (1^05.
3$. Kolthoff cM Xeltiaon, *pJ. nostra fltratloas/ Vilfiy & Sons,
lis-./ Tbrli, l^E. l>. Iftp.' 30. Saltfeoff eaS I4gaaa Hlblarog?ap1^tw Intersdenca S^ioSjers,
Ecu Tor!:, 2^H. 21. Groppt A. H. ItejaMishM Steta.
32, Vcn ^/asclherghe, ISeOos-. cad Jisrrs. . m* gjffl. &o.p. |u
009 (W).

fhe author wishes to egress sincere appreciation to St. C, 3, Pollard, the director of this research project, for Ms eneeurageiseat and assistance throu^toitt the project.
Sincere appreciation is also caressed for the a&viee end assistance of Ur. 0. B. Reid r.nd Dr. A. B. dropp with respect to the use of the spectrophotometer and the polarogr&pa.

mommtm, mmm
She rather was lorn at lloctpaie, feanesaee,, on June 18* %$Zh* Ho did Ms pre*eellege war?* at Chattanooga, Soeeftiaarlc, and Selivar, Sennessoo. Ee attended Arkansas A & II College, Monti-cello, Arismsae, frea Jane, 1$&2 to June, 1^3, rad then enlisted in the \h s, .Arssy. He received a tae&ieai discharge la January, 19$** tn Jane; lp?^>, he entered Tksridson College, Davidson, Sforth Carolina, end regained in residence there until he received his B, S. degree in June,
He entered the Graduate School of the University of florids la September, 19**6, end'received Ms I-!. S degree in June, IpAS, vhile attending the Graduate School the sxithar was a Qradaate Assiet-sat for one year cad held a Graduate Fellowship for three years.
He is a ncabor of Cama Sigjna Spsilon Honorary Chemical fraternity and Is a jollier nenber of the 'Aeericaa Chenieal Society,.

JThie dissertation mm prepared under the direction of the C&aiirasa. of the candidate* s Supervisory Ooseaitte nil has .$ee&-spprwed tgr all rses'berB of'the- coaanlttee. It was- suhaitted to the Graduate Council and vas approved as partial fulfilment of the requirements for the degree of Doctor of Jhllooophy.
Supervisory Comitteot

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