Oxidation Ofsemicarbazide, Thiosemi- Carbazide, Carbohydrazide

- c ~ ..,

Indian Journal of Chemistry Yol. 32A. October 1993, pp. 921-924

Oxidation of semicarbazide, thiosemi• Experimental carbazide, carbohydrazide, thiocarbo• Cobalt(III) solution was prepared by the anodic hydrazide, thiocyanate, thiourea and oxidation in a divided electrolytic cell consisting their derivatives with aquocobaltic of platinum electrodes. The anolyte consisted of ions in acid media 200 cm3 of cobaltous nitrate in HN03 (1.0 mol dm-3) or cobalt(ll) sulphate in H2S04 (3.0 mol dm-3') or cobalt(ll) perchlorate in HCI04 (3.0 S D Ravi Prakash t, B S Sherigara* & A M Abdul Khader mol dm - 3). The catholyte was the corresponding Department of Chemistry, Mangalore University, acid solution of appropriate concentration. The Mangalagangotri 574199, India temperature (5°C) was controlled by an ice bath. Received 8 December 1992; revised and accepted The electrolysis was carried out at a cell voltage 10 February 1993 of 6V and anodic current density of 2 miDi amps Conditions have been verified for the electrogenera• cm - 2. The concentration of Co(III) generated was tion of Co(ill) from Co(ll) in aqueous nitric acid, sul• determined by adding an aliquot to an excess of phuric acid and perchIoric acid. The Co(ill) species KI solution and titrating the liberated iodine with formed have been identified and characterised. The a standard thiosulphate solution. The value was stability of a standard solution of Co(ill) has been further checked by adding excess of standard ir• studied and conditions for the volumetric determina• on(ll) solution to an aliquot of the electrolysed tion of the probable number of electrons involved in solution and titrating the excess Fe(ll) with Cr(Vl) the oxidation of certain classes of compounds by solution using barium diphenylamine sulphonate Co(ill) in different acids, have been investigated. Oxi• as an internal indicator. The UV-visible spectrum dation products have been identified and the stoichio• of the species in 1 mol dm-3 HN03 medium metries established. The number of electrons involved showed two peaks at 600 nm and 400 nm with in these redox reactions are dependent on the nature of the reductant molecules and the reaction condi• molar absorptivity of about 40, corresponding to tions. the expected electronic transitions. Semicarbazide hydrochloride and thiosemicarb• azide(TSC) (Loba-Chemie, India) were used after In previous years considerable amount of work recrystallisation, Semicarbazones of aldehydes, on kinetics of redox reactions of Co(III) species benzaldehyde, 4-chlorobenzaldehyde, 4-nitroben• has been carried out and it has been reviewed by zaldehyde, salicylaldehyde and benzaldehyde thio• Davies and Wamqvistl and Waters and Littler2. semicarbazone and the metal comple'i,es, The instability of cobalt(III) solution involving M(TSChSO 4 (M = Ni2+ , Zn2+ or Cd2+) were pre• pared by the literature method7,8. Thiocarbo• Co;; or CoO~~ is the major hurdle in its use as an oxidising agent. However, at moderately high hydrazide (TCH), zinc thiocarbohydrazide com• aCidities and at temperature nearer zero degree plex, Zn(TCHhCl2, and carbohydrazide were pre• pared by the methods described elsewhere9• celsius, Co~~ can be obtained in a stable form and can be used in redoximetric studies. Back titration method As a part of the kinetic and analytical investig• cm3) ations of metal ion oxidations3-6, we report herein, To a known volume (VI of the reductant Co(llI) oxidation of semicarbazide, thiosemicarba• (5.0 cm3 of 0.001 mol dm-3, in a medium of 3.0 mol dm - 3 of the acid) was added a known excess zide, their derivatives, their higher homologues, of the oxidant (25.0 cm3 of 0.002 mol dm3) and namely, carbohydrazide, thiocarbohydrazide and the reaction mixture was allowed to stand for dif• certain other reductants like thiocyanate and thi• ferent intervals of time to ascertain the comple• ourea, by cobaltic ions in nitric, sulphuric and tion of the reaction, in a water bath maintained at perchloric acid media. Because of the synthetic importance of these compounds their oxidation 5 ± 2°C, with occasional shaking. Excess oxidant' reactions might be important. was determined by reacting with an equivalent amount of potassium iodide and then titrating with standard sodium thiosulphate solutiQIl to the 'Present address: Nehru Memorial College, Sullia, Karnataka. starch end point (the titre, V2 cm3). A blank titra- 922 INDIAN J OHEM, SEe. A, OCTOBER 1993

Semicarbazones in H2S04 and HN03 medium . same ali uot volume of Co(III) under id ntical reacted in two stages, namely two electron oxida• , conditio s (the titre V3 cm3). The number f elec• tion of the semicarbazones with the regeneration tronstion was]perfOrmedinv lved in the reactionsimultaneouslyis given by Eq.tak]'(1)g the of the respective aldehydes and two electron oxi• dation of the aldehyde to corresponding carbo• xylic acid. Here again in .. (1) C6HsCH = N - NH - CO - NH2 + H20 + 2C03+ • C6HsCHO + HN = N - CO - NH1 + 2C02 + + 2H+ wherethiosulph~tex landandyarethe reductantthe molaritiesrespectivelyof the. sbdium ... (4, C6HsCHO + 2C03 + + H20 - C6HsCOOH + 2Co2+ + 2H+ ... (5) ~ ous HN 3' H2S04 and HCI04 contains C ;q+ or • Co(OH);. as reactive specieslO• The pu lished perchlonc acid medium, the first stage of the reaction involved 4 electrons. The second stage of value]]ResultsIt has fIdreenthediscussionestablishedequilibriumthatconstantcobalt(III),(Kh) in~aque•f the reaction, reaction i.e. oxidation of aldehyde to carboxylic acid was relatively slow in all the three acid media Kh and the whole titration took 45-60 min. The alde• 20 <= CoO~q~ + H+ hyde formed could be identified in the initial stages of the reaction, by its 2,4-dinitrophenyl hy• drazone derivative in all the three acid media. Oxidation of TSC and its derivatives by aquo redox po ential (EO) of CO;q+/CO;q+ couple n non cobaltic ions was drastic and yielded reproducible I complexi g aqueous solutions like nitric a id or 6 electron stoichiometry in all the three media ~. perchlori acid media has been reporte 11 as is1.86(2 ± Q.1) 21O-3.molV versus dm-3standardat 25°C.hydrogenThe elest~dardtrode (Eq.6) at, [H+f 3.0 mol dm-3. \ H2N - NH - CS-NH2 + 6C03 + 5H20 - Co(III) solutions (1-3.0 x 10 - 3 mol dm - ) pre• + pared by the anodic oxidation of Co(II) s lution CNO- + 2NHt + SO~- + 7H+ + 6Co2+ ... (6) at low c rent density ( - 2 mA cm - 2), at oder• ately hig acidity (1-3 mol dm - 3) and at n op• NHt and SO~- were identified as the products erating t mperature, below 5°C, were mod rately by Nesler's test and BaCl2 reaction (in nitric and stable wi h less than 2% deterioration per 12 h. perchloric acid media) respectively. An attempt to The sta lity of the solution in different media detect CNO~ was not successful, probably be• were fou d by monitoring the changes in c ncen• cause free cyanic acid (HCNO) which was liberat• i'i'1',· tration w th time by iodometric method. Th stab• ed initially was decomposed into CO2 and NH3 iUties of e solutions were in the order: nit 'c ac• and the latter combined with the H2S04 present - t i " id > sulp uric acid> perchloric acid. to form ammonium sulphate. A little of the cyanic ~ acid, however, was not decomposed and was re• I The st istical data obtained from these r~doxi• cognised in the evolved gas by its penetrating metric s ies are presented in Table 1. odour. ,t'1 , In case of benzaldehyde thiosemicarbazone, the mediumSemica nderwentbazide in twonitricelectronacid andchangesulphuri~oxitlationacid ,I reaction proceeded in two stages by the regenera• by Co(III as with Mn(III)12,13. tion of benzaldehyde and further oxidation of benzaldehyde to benzoic acid.

H2NH2N- c

M(H2N - HN -CS- NH2)2S04 + 12C03++ lOHzO•

NHtCO2 + wN +identifiedNHt + 4C02in +the+ 3Hreaction+ mix~ref .. (3)by 12Co2+ + 3S0~- + 4NHt + 2CNO- + 14H+ + M2+ Nessler's est. ... (7)

I

l!i .1""" 'I' " """ L." 11.11 11!illll,1 1111".11111.111 'Iitil NOTES 923

4.1 ±0.02 p-ChlorobenzaldehydeBenzaldehydeSalicylaldehydem-Nitrom-Nitrobenzaldehydep-ChlorobenzaldehydeSalicylaldehydeNi(TSChS04ThiosemicarbazideZn(TCHhCI2ThiocarbohydrazideZn(TSChS04CarbohydrazideCd(TSChS04BenzaldehydeRJtassiurnbenzaldehyde15Tablethiocyanatesemicarbazone5,89±0.025.91thiosernicarbazoneH2SO42.046.0712.09±0.062.086.055.923.94±0.03(312.0811.973.0712.04±0.021.953.963.893.97±0.031.93HCI042.051.965.9611.93±0.0211.943.067.918.115.9511.93semicarbazone4.13.9I-Volumetricmolmoldm-3)±O.o1(TSC)±±0.02±O.ot±O,02±0.03±O.o1±0,02±0.01±0.02±0.04(TCH)±0.02±O.ot±0.01±O.o1dm-3)0.01semicarbazone0.01semicarbazone(0.11-0.45)determination12.06±0.0212.0411.9411.916.060.807,882.033,933.965,943,951.963.911.95Number-2.94±0.02±±0.04±O.o1±0.Q1±0.03±0.02±0.01±O,O1± 0.020.060.01of probableof electronnumberparticipatingof electronsin involvedredox reaction"in the oxidation± SDb of certain compounds by "\, , 11(0.08-0.33) >. (1 mol dm-3) ~ Co(lIl)in acid media at 5 ± 2°C (0.28-1.67)(0.26-1.06(0.35-1.40(0.52-2.08)(0,37-1.51(0.49-1.97)((0.11-0.44(0.40-1.63)(0.30-1.22)(0.02-0.76)(0.44-1.79)(0.02-0.10)(0.02-0.09)Sernicarbazide(0.09-0.34)(0.09-0.39)(0.08-0.34))) (range19' ThioureastudiedCompoundin mg) 1810161417121398654237 (0.96bStandard

corresponding disulphide with a single electron carboh drazide quantitatively with 4 and 6 elec- change (Eq. 11) tron tr sfer process respectively in all t e three acidCo(~)m ia.ions oxidise carbohydrazide atd thio•

-CO~NHNHz+4C03+ +HzO H2N\(-5-5-( jNf1 ~ ~ '..(II) HN NH -CO-OH+Nz+4H+ +4Coz+ I '" (8) HzNH - CS - NHNHz + 6C03+ + 6H20 H2NH -CO-OH+2NH; +SO~- In the present work, Co(III) oxidation of thiourea + 6H+ 6Co2+ '" (9) was carried out under oxidantexc~ss condition, and it was observed that the reaction proceeded The rmation of the oxidation roduct, t beyond the disulphide stage as indicated by the H2NHN - CO - OH is supported by the e idence higher stoichiometry in Table 1. However a re• recorde in the literature14. In the case of Co(III) producible 3 electron change stoichiometry could oxidatio of thiocarbohydrazide in aq. H 03 or be established in all the three acid media. aq, HCI 4, NH: and SO~- were identifie as the products by the Nessler's test and bariu chlo• To summarize the analytical utility of aquo co• ride re tion, respectively. Further, SO~- was baltic ions in three acid media has been tested gravimet 'cally precipitated as BaS04 an from with reference to certain hydrazine compounds the esti ated weight, the 1 : 6 stoichiomet y was and sulphur compounds. The number of electroqs further e tablished. released by these reductants depended on the re• Oxidat on of thiocyan,ates was carried 0 ductant molecules and the reaction conditions. in (i) re uctant excess condition and (ii) Common anions such as HSO", PzO~-, CIO", excess co dition. NO;, Cl- and F- did not interfere in these reac• tions, but Br-, 1-, S20~- andhydrazine inter• known amount of thiocyanate ta en in fered. cm3 of 0.01 mol dm - 3) in a eaker known quantity of the oxidant (5.0 cm3 of O. 02 mol dm-3). Thiocyanate redu es all the Co(II ) present in the solution. The exce s thi• References

ocyanate as then determined by titratio with I Davies G & Warnqvist B, Coord Chern Rev, 5 (1970) standard ilver nitrate solution in dil. HNO me• 349, and references therein. dium usin ferric alum indicator. The expe 'ment 2 Waters W A & Littler J S, Oxidation in organic chemistry, revealed t at Co(III): NCS - ratio, in the re ction edited by K B Wiberg (Academic Press, New York) 1965, was I : 1. p, 185-241. 3 Ivan Pinto, Sherigara B S & Udupa H V K, Bull chern (ii) To known amount Soc,Japan, 63(1990)3625. 4 Ivan Pinto, Sherigara B S & Udupa H V K, Analyst, 116 added kn wn quantity of the oxidant in e cess. (1991)285. The back 'tration of the excess Co(III) by io om• 5 Ishwar Bhat K, Sherigara B S, Ivan Pinto & Udupa H V etric meth d yielded the stoichiometry of 1 : 0,8 K Indian J Chern, 31 A (i (92) 49 .. instead of 1 : 1. This discrepancy is at1ribut d to 6 Ishwar Bhat K, Sherigara B S & Ivan Pinto, Trans met Chern, 18 (1993) 163. the produ , (NCSlz also oxidising the adde KI 7 Vogel A I, A text book of practical organic chemistry, to 12 whi h takes up proportionate exces of (Longman, London) 1958,p.11I2. Na2S203 t give higher titre value. The ov raIl 8 Mahadavappa D S & Ananda Murthy A S, Aust J Chern, reaction ca be represented by the equation: 25 (1972) 1565. 9 Kurzer F & Wilkinson M, Chern Rev, 70 (1970) 111. 10 Rosseinsky D R, Nature. 216 (1967) 791. 11 Warnqvist B, Inorg Chern, 9 (1970) 682. 12 Trugut Gunduz Esmakilic Adnan Kenar & Guloztoes, extractedT he covale itht dimer,chloroforma pseudohaIogenand on passing(NCS)z,c was0• Analyst, 114 (1989) 227. rine gas, de CSeloped- -+ 2Co2+turbidity+ (NCS)zdue to the forma. ,. ~1O)ion 13 Ivan Pinto, Sherigara B S & Udupa H V K, Proceedings of a white sid, SCNCJl5. of the 9th annual conference, Indian Council of Chemis• try, Gulbarga University, Gulbarga, India, 1990, p. 120. 14 Krivis A F, Gazda E S, SUpp G R & Kippur P S, Analyt, ganic deriva ives with sodium vanadate, hexac an• Chern, 35 (1963) 1955. 15 Heslop R B & Jones K, Inorganic Chemistry A guide to and manga ese(IV) have been carried outl6. In 539.advanced study, (Elsevier, Amsterdam, Oxford) 1976, p. mostoferrate(I1I),Determinof the tioncencases'um(IV)ofthioureathioureasulphate,getsand oxidisedsomemanganeseof toitSitheIII)or• 16 Singh B & Verma B S, J Sci lnd Res, 24 (1965) 536.