STUD~ OF TAUTO.MERIS.L ~. A N D GEOMETRICAL ISO.XAERISM

IN DERIVATIVES OF CARBON~L COMPOUNDS

CONTAIN!XG NITROGEN

COMMUNICATION 10. INF'?.-~JED SPECTIL.~ OF PHEN'~ LHYDRAZONES

OF SOME ALDEH'~ DES

R. R. S h a g i d u l l ~ n . F. K. S a t t a r o v a , T . V. T r o e p o l ' s k a ) a , a n d Yu.

A. E. Arb,.tzov Chemical ~.~urate, Academy of Scmnces, USSI ~, Translated s lzvesti)a Akadem~x Nauk SSSR, Otdeleme Khumcheskikh Nauk, No. 3, pp. 473-4"/8, March, 1963 Original arracle submmed June 6, 1962

P. K ~ t a e r

The results of a polarographlc stud) on phenylh)drazones of se~ ~ral aldeh)des and ketones reported prevmusl) [1-4] mdlcote fi'~t tau tomenc transmons proceeding according to the general scheme

enh~dmzme ~ hydrazone -- azo form

occur m a!co~ol-~,ater solutmns. It ~,as somewhat surprising, albe~t m agreement ~lth data on the chenl~,cal nature of these substances (Flsher's reaction), to note that the polarograms of phcn)lh)drazones of ahphauc aldeb)des and ketones in freshly prepared alcohol-~,ater solutions show, first of all, a ~,a~ e caused by the enh)drazmtc structure. The amphtadc of th~s ~,axe deohncs rapidly, with stmultaneom formauon of wa~ es related to reductton of the enh)- drazmm and azo forms, at more posm~e potenualz. The most probable assumptton seems to be that phe,tyth)dra- zones o f a h p h a u c aldeh)des and ketones m the free state possess tht. enh)drazm~c structure, for Lt ts dfffu alt to un- derstand ~hy tke original h)drazone, ~,hen dissolved m alcohol, shouid be corn erred very rapldty to the enh)dra- z lmc structure and, during storagL: of the soluuon, be retransformed into the h)drazone. In thLs connect~oF1 it ~s tn- terestmg to compare the result~ o f the polarographm study with data obtained by mcam of other methods,

In the pr,:seat commumca t :on ~,e present the results found tu a stud)" on the infrared spectra of phen)lhydrazon,.s of some a h p h a u c and a romauc a!deh}des. When we were preparing thts paper, there appeared a comnmmeat,.on on an analogous invcsugatmn [5]. The present paper differs from the one just menuoned m that it deals with a more c \ - termve class o f compounds and m flxat the spectra were studied in greater detad. Pubhcauons have appeared also o:: a spectral stud) o f dimeth)lh)drazones of ahphauc aldehydes [6], and of tht. ~tmpiest unsaturated dtalk~Ihydrazoncs [';].

We studmd the infrared spectra produced by the phenylhydrazones of formaldeh)de, acetaldehyde, prop~onal- dehyde, benza!d~h)de, and the ~sobut)nc, ~so~alertc, and cmnanuc ald~.b)des, and also the methylphenylhydrazonc of benzaldch)de. Thetr spectrograms, and also those of amhne, phen)lhydrazme and 1,1-meth)lphcaylhtdrazmc, which were used as auxaliar) sub~tauccs, are reported below (Figs. 1 and 2)

The ~ e c t r a of the compounch mentmned contain many d~stmct, rather sharp absorption maxima, as are usually found m conjugated s}~tems, tn the spectra of phenylhydrazones of aldeh)des at tcnuon is drawn primarily by several bands which hardl) chang~ ,n pos.mon from one compound to another and which, m most cases, are evtdcntl} related to the benzer~ ~ing.

Frequency, cm "t

70O 745 885 990

1060

The fr~que~cies of these peaks and a po~.sible lnterpretauon are gKven below,

(Yat-of-plane C-H deformatmn of a monosubsututed benzene

Combir, ation frequenc) of the a romauc m~g ~Lsauon frequency of the ring Planar C-H deformauon vtbrat~on of a mono~ubsutated benzene, preferential change of

N-N imo N-N=C

425

1135-1165 P ~ C-H deformatton w b r a u c n of a ~onc6ubstit 'uted be~-~zene,

o f C - C into N : C - C 1260 Ar-X 1305 Ar -N 1500

1600 0

preferenual c~. nge

Moreover, the spectrograx:_~ .zf al l examined phenylhydraz,~zcs of aldeh}des show ab~orpts bands at ,.-3000 r -l , which arc related to v N-~, vz lence ~ibratml~. These ba.~Zs z:c of !ow mtenstty ~ t h an absorptton co~ffic,enc

of the same order as that of C-r~ v a k r.ce : ~brauom of the benze:;e nn~._ h hen the compomnds are &ssoh ed m CCI~, the bands shift 30-40 ctn "1 to+a:2 E~o~er wavelengths. It ma} Be .voted that the observed pzcture ~s analogous, to t ha t

noted in secondary a h p h a n c an-_z_.~ [~].

In the range of a romauc C-H valence ubrataons a l l com?o.mds exa.mmed have, as a vale, three bands wmh maxima at 3020, 30t;0, and 30OC~ c m -z, the mtensmcs d e e h n m g ,n tk.e ~ame sequence. The Uas and ~'s ~ b r a u o m of CH~- and CH-groups appear m zhe frequency rang~, e h a r a c t e n m c of h)dtocarbons. Deformatmn wbratmnz of methyl and methylene groups m zZ<~l radmals show absorptmn , : z : c ' a 1)rag at the customar) posxnons, ~.e.,+tt

6CH a = 1470 cm "t, 6asCti~ -: 14~C+ c m "z. Moreover, a d d m o n a l ~:a.xm a at 1.4-t4 cm "~, wbach should be rclated to vibrattons of the benzene nng [91 aze observed m the spectra of ~e a!deh)dc derivattves. A low peak at 1428 cm "z. which extsts also m phen)lh)dza-~_z.v~e and meth}lphen}lhydrazme axd probably a b e m the spectra of przmary amme~ and diphen}lamme, appears m r2~ L:xctrogram of the phen}lh}dzazone of tsox a l e n c aldeh}de.

In the range of 1310-139~. cz~ -z a l l examined compounds ShOW an extended series of maxuna, whtch may be

ascribed to OsCH3, 6C11, and to ~ o n and hbrat ton vibrations of Ctt-bonds in methyl and meth) lene groups, The appearance of weak bonds at ~uS l cxa "l and the changes obsep:cd m the 1100-1800 cm "x ranges of the various sllb-

-1 ~00 300 1100 ~Jr ~500 v. cm

J t t I 0 I n �9 i !

~ C6"sNHNU z

C6H5 - N- NH.~

I ~l C6HsNHN=C-H j~ r~ .r~ !V 5,J L

Fig. 1.

-! 7t~l 900 nO0 t3t'O lbO~ v r m

o ~ t , , ~ ! t t ,

+

Fig . 2 .

426

.~.anees are p:obabl) due to C-C _-~nl v.h=atioc~, and a~o zo in-plane and out-of-plane (~n rcL~Xcn to ~e pla.~=e of ~ r three n e a : e ~ atoms in *.e =_~Lec'q=!zz ~-eleton) tomion vibrations of CH3. The m t e r ~ v e ~eak at_ 972 c m - : in the %.~ectram of ~,.e phenylh)d.,~zr ~f cLv_nz=~c a ldeh)de ~e-,.Qd be related to the wekI-l<~nown cV~-~cteristAc CH vibra-

I t ion o f the trar_~-configuranoe. (~ = C . The spht tmg of r_he 745 cm - t band in r_he spectra of t~m compound and of

d~e phenyI~hydrazone of b e r ~ z a ~ y ~ : e is ev ident ly caused by the two monosub~tltuted benzene . ~ . ~ m the ~nolec'ale.

T h c ~ spectra l features ~,~zch per : ra t the occurrence of defini te tautomeric forrvm in the e ta :vaned compounds to be es~abhshed are most l n t e=~z=g . Vken)Lh)drazones m a y generaL1)' exu~ ~n three t au tomenc form~, wheh are

d i s z i n g u / ~ d by the posmon o f "~.e d o u b ~ bond

/jCH II <~IIH.R ,C;I.R " " (azo form). (enh)~=az~ne) ~ Ar--NII--N=C (hydrazone)~ Ar--N=N--CI|~H

it ,s known tha t bonds formed ~,~'fn pa., ' t iclpation of a mtrogen atom yield absorpnon bands ~,h~ch are hlghl) vat ,able bor~, m postion and ~n mterm~. . ' -? , . .e m.'=ge of C~N- frequencies often comrades with that of C=C-bond fro.quenches, ar.d only i f the corresponding a ~ - - p r J o ~ ~s ir~tenstve, cau a d~stmct~on be made bet~,een the t~,o ~)pes of frequencies. The N=N bond vibrat ton ~s tm'~,z~lly fo=nd a t longer wavelengths. The fact that ab~0rpnen ban~.~ co=espondmg to an NH group are present m the sFec'.z~ o r a l ! e ta : r imed ph~nyLh)drazones of a ldch)des points to fine existence of the en- h ) d r a z m i c or the hydrazonte ~r.~7.zome.-ic fom~. It ts dffflcu!t to find an) evidence of an N ~ N - ~ - d m the spectro- g,--a;~_~, though in some cases ;~e no~ed a Io , ,ermg of the vNH intensity when recording infrared ~pectra m a CCI~ so- fur-ion and ~ i s is ~ndtrect md~c.zz~c~ of ~a rua l conversion of the dts~ol~ed eompomnd to the a=~ %rm. O'Connor, ~ho e.xammed [5] the infrared spec~z.~ of so:no phen)lh]cdrazo=es d~ssol~ed m nonpolar sohe.nts, a=~re2 at a s~nukar con- clusion. In our case norther ff.e po~.anc=x nor the mtcp-~.t) of the absorpnon m the range where double bonds appear permi t of dtst ingmshmg bet~,ee~ r_be h)d.-azomc and the emh)drazlmc forms. The corrcspon&ng hand ts supenmposcd on the peak of the benzene rtng z t 16~0 c m "~. The very weak absorptton at ~1550 cm "t is to be ascribed to 6Nt f

An examina t ion of the s~-~e~zraI ~.,:ge 750-1000 c m -1 ,,~elds valuable mformatmn on the F:esence ot a g~ven mutomef ic form. Structures o f "Cv~e er2:)~razmtc t )pe must manifest themselves m the absorption range rel.~tmg to o u t - o f - p l a n e CH deformatmr~ ~-~bzaraoe~ in the N-CII=CH~(R) system. These frequencies are rezy characte: isnc of tLxdrocarben_~ and appear as ve~- ~zreng ak~orpnon max~rr.a. It is also known that m most case-~ ~.kere a C=C group = eomnected to atoms other tka~ c~zrbon, wr tua l l ) tdent ica l md~cat to~ are obtained. However, ~l-.en the C=C group adjokus an ox)gen atom, a I a r ~ z ~ of rA~.e absorption band towards lower frequenctes ts noted. ~t ~s difficult to state beforehand ~ha t wall be fou.~d ~ zhe cas~ of a mtrogen ~tom, but the mate r ia l at our d~sposaI d~::s not permit ex-

r nhe posstbthty that the 2 ~ o r p t i o a peak of = C - - l ! m the N-C--C arrangement may also be lowered m mten- I

H(R) ~aty and f requen t ) , t lowe~er, u~ arrangement ~s accom~amed by absorpnor, of average or h~b~: ( in relat,3n to the o ther band~) intensity tn the r a~e . ment ioned . In fact, in the speetrum of the phenylh)drazone of formaIdeh)de, the

N-N=CH z group produces an a~orT, non ol a~erage mter~ . : ) between 880 and 925 e r a " , t , e . , m t.he normal range of

=CH~-valcnee ~ ~bratm~.

C,,I .NCII~NCH~c<C~:, , ,hich we s)n~[-~-~zed as a model 1-Phenyl-1 ,2-dtmeth .~!- i -~sopropen) !h)dra zme,

~ractur , : [4], also g,~es a ra the: dasnnct a~orp t ton band at 854 cm "t. However, the spectra of a l l e.xam~ned pbe~yl- hydrazone~ of a ldeh)des contat.n ~-o aL..~=pt~on bands that :=~s be ascrtbed to ou t -o f -p lane v tb :anons of C-It-bonds a t t ached to a C=C group. ~ e ~drmt f i a t the phenylh)drazone of ace t a lde i~de s,hov, s an ab~o~aon maxm~um at 812 r "x, wtuch, however, as men~oncd above, ~s much below the value of 854 c:u "t found m N-C-Cl t : , and can hardly be interpreted m the way outhn.~J above. Neither can the ab~orptmn band at 85~ cm "~, found ~n a l l substances, be ascr ibed to ~'~branons of C [ t - ~ _ 2 s a t , ached to a C=C groap, s~nec fl~e correspovd~ng f icquency .~ constant, and more- over, occum in the spectra o f z . ~ n e , ~,enyl2~)drazme a~:d methylphcnylh)~razme. The excc~r con:~tancy of the maxamam of th~s band suggest~ ".L=t '.t ~s a combinat ion v tbranon of the benzene ring.

The data obtained alIo~. ~ to conclude tb.at phenyE-.ydrazones of a ldeh)des have the h )d rzzomc structure, both in the puze ~tatc and m frc~hiy 7_~;xa_,-ed ~ l . , t i o ~ m CCI~. This conclu~,on ~s also ,n agreeme=t , . i th data m O'Con- noffs i~aT, e r [5]. in the compou=,~ cxa::~.ff~d the ab~orF~io~u frequency due to the C--N-bond eq-.:als ~1600 cm "t. *lhe spectra o f r2;e pl enyH~>drazone~ c f ci~c~a::-Ac aldelDde a~d b~.~zzaldeh)de show a d d m o n a l max.~=-.a m the range from 15.00 to !~r c m "t wPuch are c.z_~.d b: a coujugat~d s~ste=~., The C :N absorption band ob~." ,ed .'n the phenylhydta- zone of fo,,Tna'~deh)de he~ a~ t 5 - ", cm "~t. Y.ere, th,~ be! a ; , c r of tht: band ~s ewden t ly a~alogot.~ :o that of the C=C-

427

bond, ~ frequency of ~h/ch increases ~,-itL r_ke woamber of subsutuen~, k ~_c:fi~. be emphasized here that the C :N-

bond frequency is lower than u~aally repo.-ted ~1] . A noticeable r p . co.%~::~adon m ~.e s)-~tem O -N-N=C 15,

obviously, one o f the causes of tins la~ering. TbAs h)pothesi~ is confirmed 5~ a ~ in ~ e C=N-borA frequenc) ob- served in the spectrum of the mer.hylphen)Lh)drazone of benzaldeh)de t1612 c.-n_. -1, compared ~ith 1602 cm "1 in the phenylhydrazone of benzaldeh)de), ~ance introduction of a meth) l Stoup d~-.:.-~ t~e cenjugation of the molecular s)s- tern. B~ief reference should be wade of ~ e fact that here as in mefin)lhydTazine attach,-nent of a methyl group to the nitrogen atom is accompanied by tke appearance of a new cha rzc t e r~ l c ~ x i m u m at 28.02 c m " I [12], it must be remarked that introduction of a meth) l group radically ckanges the emL-e s~ectral picture. Consequemty, all bonds and groups participate to a con.~derabM extent in the v a n o ~ molec,J-~: v~brat~or~ of the compound~, examined. This, in its turn, points to a high mobili~) and generalization of the elect~on cloud, as is na t~a I m such conjugated s)~tems. The polarographic data aRo pow, t in ~as direction [4]. The concI'~.m'on of o ~ discussion ~s that alI assign- ments reported above cannot be taken as characteristic frequencies, but ~ole'~y as ind~catiom vahd for the series of compounds cons:dered.

E X P E R I M E N T A L

ALl compounds emplo)ec~ in the present ~.tud) were s)~thesized b) rite vc.:a! methods, their comtam~ coincide wxth the data reported m the hterature. The methods of preparation and ~ue ?mperhes of benzeneazomethane and 1.2-dimeth~l-2-1sopropenyl- l -phenylh)drazme have been d ~ c n b e d prev to~!y [4]. The spectra of those compounds whxch are sohd under normal conditmns ~,ere taken m vaseline. The abso~t lon bands of vasehne m the correspond- mg spectrograms are indicated b) vert ical dashes. The spectrograms x, ere recorded in IKS-14 and UR-10 spectro- graphs provided with NaC1 and DF prisms. The spectral sin width was 5 cm "1 at 500 cm "I, 4 cm "1 at 1000 cm "i, 6 cm "1 at 1500 cm "I, 3 cm "1 at 300~ cm "t.

S U M M A R Y

1. Infrared spectra of phen)lh)drazones of some aldeh)des have been meamred and discussed.

2. In the free state these compou~,ds possess the h)drazomc stmcrare.

3. ~rpTr-Conjugation is found in the Ar-_NH-N C-bond s)stem.

L I T E R A T U R E C I T E D

1. A.E. Mbuzov and ~ u. P. Kitaev, Dokl. AN SSSIL 113, 57"i (1957). 2. Ytt. P. Kltaev and A. E. Arbuzov, izv. AN SSS.R. Otd. khml. n., 1957, b337. 3. Yu. P. Kxtaev and A. E. Arbuzov. Iz~. AN SSSR. Otd. khim. n.,19G0. 14~_~5. 4. Yu. P. Kltaev and T. V. Trocpo1'ska)a. Izv. AN SSSR. Otd. khm~. n. ~L ~. press). 5. R. O'Connor, J. Organ. Chem.. 2_6, 4375 (1961). 6. IL H. Wdley, S. C. Sin)maker, and H. Kraus. J. Organ Chem., 22___. 2C4 (1957). 7. B.V. Ioffe and K. N. Zelemn, Dokl. AN SSSR. 141, 1369 (1961). 8. L.J . Bellamy, The Infra-Red Spectra o f Complex Molcculcs, Mcrhuer~ London (1960). p. 252.

9. Ibld., p. 72. 10. [bid., p. 220. 11. M. L Fabian~ M. Legrand, and P. Poiner. Bull. Soc. chlm. France (195,~), 1499. 12. K. Kohlrausch, Raman Spectra [Ru~ctan tramlatlon], IL, Moscow (1952). p. 257.

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