Goyal, R. N.

Malik, Vahid U.

English

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INDIAN J. CHEM., VOL. 14A, MAY 1976TABLE 1 -MELTING POINT, ANALYTICALANDMOLECULARWEIGHT DATAFOR (C.H,).SnCla.n AMIDEAmide n m.p. Analytical data, found (calc.) %(0C)Sn C H N Mol. wtfound(calc.)N-Ethylformamide 1 65 28'5 43-2 404- 3-9 248(28'5) (43'2) (4'1) (34) (417)2 73 25'0 44-1 4·8 5'8 296(24,3) (44-1) (4'9) (5'7) (490)N -Ethylacetamide 1 57 27·8 44·0 4·8 3-1 246(27'6) (44'5) (H) (3'2) (431)2 63 23'5 45·9 5·4 5'1 300(22'9) (46'3) (5'4) (H) (518)N -Butylacetamide 1 58 24'8 46'8 5·4 2·9 280(25'9) (47'1) (5'0) (3'1) (459)N,N'-Diethylformamide 55 26·6 46·1 4·8 3·0 260(26'7) (45'8) (4'7) (3-1) (445)2 59 21'2 48'4 6'1 5·4 302(21'7) (48·4) (5·9) (5'1) (546)N,N' -Diethylacetamide 2 76-78 21'5 50·0 6·3 4·8 392(20'8) (50'1) (6'3) (4·9) (574)N,N' -Dipropylacetamide 2 90 19·2 53'5 7·2 4·4 430(18'9) (53'3) (6'9) (H) (630)N,N'-Dimethylpropionamide 1 55 26·9 45·7 4'9 3·1 272(26'7) (45'8) (4'7) (3'1) (445)N,N' -Dipropylpropionamide 1 62 24·7 50'5 5·6 2'8 293(23'7) (50'2) (5'7) (2-8) (501)In the case of compounds with secondary ami des, 4. HARADA, T., Bull. chem, Soc. Japan, 4 (1929), 266.complexation i~ ~upported ~y a small negative s?ift Jr SRI(~~;~t~3r N. & MISRA, B., J. organometal Chem, 32,(Llv=7 ± 3 em ) In the amide-If band. A medium v6. TANAKA, T., Inorg. chem, Acta, 1 (1967), 217.to strong band due to a deformation mode of ./. TANAKA, T. & KAMITANI,T., Inorg. chem. Acta, 2 (1968),O=C-N, appears in the range 575-650 em? in the 175.spectra of the pure arnides. On coordination thisabsorption is shifted to higher frequency region by11 + 2 crrr-.in conformity with our earlier observationss, theSn-CI stretching has been identified at 365 crrr- inthe spectrum of tetra-coordinated diphenyltindichloride. In the spectra of the adducts, thisabsorption occurs at 278 ± 10 crrr". This signi-ficant lowering of the absorption frequency isthe characteristic of increase in coordinationnumber of the metal atoms-". Two absorptions ofmedium intensity in the regions 260-290 and 235-250cm-l are assigned to asymmetric and symmetrictin-aryl stretchings, New spectral bands of mediumto strong intensity have been noticed in the narrowrange 335-342 em+ in the spectra of the adductswhich are not present either in the spectra of pureamides or the Lewis acid. These bands maypossibly be associated with the vibration of O-J>oSnbond. From the above observations, formationof O-J>oSnbond is obvious.The author is grateful to the CSIR, New Delhi,for a senior research fellowship and to Dr T. N.Srivastava for helpful discussions. She is a'sograteful to Prof. Ram Gopal, Head, ChemistryDepartment, for providing facilities and encourage-ments.peferencesJ 1. ZHELNOV,A. A., VAVRILIN, G. F. & CHISTYAKOV,V. E.,/ cu«. Abstr., 69 (1968), 35210v."'2jJ..JAIN, S. C. & RIVEST, R., Can. J. Chem., 45 (1967),139.PAUL, R. C., GUPTA, S. K. & CHADHA, S. L., IndianJ. Cbem., 8 (1970), 1020.348Polarography of Some Arylhydrazones'VAHID U. MALIK & R. N. GOYALChemistry Department, University of Roorkee, RoorkeeReceived 7 March 1975; accepted 18 July 1975Pofarographlc reduction of I-phenyl-2-arylhydrazo-1,2,3-butanetrlones in dimethyl formamide involves4-electron transfer ~ivinil well-defined diffusion-con-trolled, irreversible reduction waves. A mechanismwhich assumes reduction of -NH-N- bond has beenproposed. Electron donating substituents, viz. OCH.,OC.H", CH3 render the reduction at d.m.e. more diffi-cult and electron wlthdrawlng substituents shift theEl/2 towards more positive potential. A linear corre-lation between half-wave potential and Hammett sub-stituent constant has also been observed.IN this note we report the resul ts of studies onthe polarographic reduction of l-phenyl-z-phe-nylhydrazo =, 1 - phenyl - 2 - (2 - methoxyphenyl-hydrazo) -, 1 - phenyl - 2 - (3 - chlorophenylhydra-zo)-, 1- phenyl- 2 - (4 - methoxyphenylhydrazo) -, 1-phenyl - 2 - (4 - ethoxyphenylhydrazoj-, l-phenyl-2-(3-methylphenylhydrazo)-, l-phenyl-2-(4-chlorophe-nylhydrazo)-, and l-phenyl-2-(4-methylphenylhy-drazo)-l,2,3-butanetriones (I). These products wereprepared by literature method",Since all these coupled products were water in-soluble, their stock solutions (1X lo-3M) wereprepared in methanol (AR). Polarograms were[log~. -0·546 log t]~d-~The value of n was found to be four in all the J. GARG, H. G. & SINGH, P. P., J. med. cu-«, 11 (1968),cases. The following general mechanism may be 1103. .put forward for their reduction: 2. DEVRIES, T. & KROON, J. L.,J. Am. chem. Soc., 75 t19S3),2484.CORI 3. WAWZONEK,5., BLAHA, E. W., BERKEY, R. &; RUNNER,/ M. E., J. electrochem, Soc., 101 (1955), 235.R-C.H.-NH-N=C ~e .. +: MElTES, L., Polarographic techniques (Interscience, New,/ York), 1967, 228.COR ~-:FLEET, B. & ZUMAN,P., Colln Czech. Ches«. Commun., 313 ,/ (1967), 2066.CORl 6. ZUMAN, P., Colln Czech. cu»: Commun., 15 (1950), 839./ 7~KITAJEV, Yu. P., BUDNIKOV, G. K. & MALSORA,L. T.,R-C6H.&NH2 + H2N-CH j Izv. Akad. Nauk SSSR. s«. xu«, 9 (1967), 1911-, 8. KITAJEV, Yu. P., BUDNlKOV, G. K., TROJEPOLSKA]A,CORs T. V. & Ansuzov, A. E., Dokl. Akad. Nauk SSR, 137(1961), 862.PATAl, 5., The chemistry of carbon nitrogen double bOtld(Interscience, New York), (1970), 162.recorded at 250 ± 0.10 in purified dimethyl formamidesusing a Cambridge pen recording polarograph(capillary characteristics, 3·75 mg2/S sec-I/2) andlithium chloride (1M) as supporting electrolyte.SCE was used as the reference electrode andpurified nitrogen was bubbled through the solutionsfor 15 min. Due corrections were made for residualcurrent in all the cases. The value of n, numberof electrons involved in the reduction process wasfound by the millicoulometric method of DeVriesand Kroon- using a mercury pool cathode.All these coupled products give one well-defined,4-electron transfer reduction wave. The limitingcurrent exhibited linear dependence on mercurypressure (40-55 cm) and to the concentration ofdepolarizer (1 X 1o-IM to 2·5 X 10-IM). These factsindicate the diffusion-controlled nature of the wavewhich was further confirmed by the low value oftemp. coefficient (1·0-1·6% deg-1). Further it wasnoted that El/2 values vary with the concentrationof the depolarizer and shift towards more positivepotential with the increase in concentration of thedepolarizer. This behaviour pointed towards theirreversible nature of the electrode process'. Thiswas again confirmed by the linear plot of Ed .e.versuswhere R] = CHao R2 = CaHII' 9-Similar reduction steps for the reduction of v .azomethine (-C=N-) bond have also been pro-posed by Zumans-s and others'.Since the primary step in the reduction processinvolves breaking of -NH-N- bond, an electron donat-ing group would strengthen such a bond resultingin the shift of El/2 towards more negative potentialwhereas an electron withdrawing group wouldfacilitate reduction by decreasing electron densityat -NH-N- bond resulting in the shift of El/2 towardsmore positive potential was found to be true for thecompounds under study.A linear correlation between the half-wave poten-tial in dimethyl forrnarnide medium and theHammett substituent constant (1 is shown in Fig. 1.The value of artha-substituted derivatives deviatedsignificantly from the linear plot obtained. Thisbehaviour may be accounted for on the basis ofsteric effects. - The p-substituted derivatives, viz,methoxy, ethoxy, chloro and methyl, fit in thelinear plot. The observed value of specific reactionconstant (P = 0·11) based on the measurement ofNOTES>0·36•....::: 0·32wIFig. 1 - Plot of E1/2 versus IJ for 1-phenyl-2-arylhydrazo-1,2,3-butanetrioneshalf-wave potentials of eight compounds to covera wide range of (1 values are in good agreement withthe P values obtained by earlier workers for largenumber of compounds containing azomethinebonds-". The positive P value indicates a nucleo-philic reaction centre in the molecule therebyindicating that electron withdrawing substituentswill facilitate the reduction and electron donatinggroups make it more difficult.ReferencesUnusual Aspects of Cadmium Reduction onGold ElectrodeR. B. VERNEKAR & R. G. DHANESHWAROpto-electronics Section and Analytical Chemistry DivisionBha bha Atomic Research Centre, Trornbay, Bombay 400085Received 7 March 1975; accepted 28 July 1975The study of cadmlwn reduction at the ~old wireindicator electrode reveals unusual aspects. Very hiabcurrents are obtained in the nitrate supportina electro-lyte, only at the aold electrode. Moreover, of all thebivalent ions, such hiab currents are obtained only forcadmium. Current-concentration linearity is obtainedfor nitrate ion and not for cadmium. Reduction ofCd(lI) to Cd(I) followed by the oxidation of Cd(I) toCd(lI) in nitrate medium bas been sul1Qestedto accountfor very hi~h currents.3-+9

Polarography of Some Arylhydrazones

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Polarography of Some Arylhydrazones

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