Research Journal of Chemical Sciences ______________________________________________ ISSN 2231-606X Vol. 3(3), 26-29, March (2013) Res. J. Chem. Sci. International Science Congress Association 26 Electrochemical Reduction of p-Nitrobenzamide at Stainless (SS-316) Electrode in Basic MediaSharma S.K., Sharma I.K. and Verma P.S.Department of Pure and Applied Chemistry, University of Kota, Kota, Rajasthan, INDIA Department of Chemistry, University of Rajasthan, Jaipur, Rajasthan, INDIAAvailable online at: www.isca.in Received 26th November 2012, revised 19th December 2012, accepted 1st January 2013Abstract Cyclic voltammograms of p-nitrobenzamide were recorded at different pH (5.0, 7.0 and 9.0) to establish the optimum conditions of its reduction. The reduction of p-nitrobenzamide was thereafter carried out galvanostatically at pH = 9.0 using Stainless (SS-316) as a working electrode. 4, 4’- icarbamoylazobenzene was obtained in which was good yield (91.2%) isolated then purified by chromatographic techniques and characterized on the basis of spectral analysis.Keywords:-nitrobenzamide, galvanostatic reduction, stainless steel (SS-316) electrode, cyclic voltammetry. Introduction Electrochemistry has been widely used in industry in effluent treatment, corrosion prevention and electroplating as well as in electro chemical synthesis. Electro-organic synthesis is now a well established technique1-2 for synthesize the desired compound by oxidation or reduction of substrate. Here electron obtained during electrochemical reaction play on important role by acting as a reagent. In the present work the electrochemical reduction of nitrobenzamide is described. The reduction potential of the reactant was recorded by polarographic techniques. Cyclic voltammetry was used to decide the reversibility of the process. Different natures of cyclic voltammograms were obtained in different medium (acidic, basic and neutral). This indicates that in different media different electrolysis products were obtained. Constant current electrolysis3-9 at stainless steel (SS-316) electrode p-nitrobenzamid gave different products in different media,but the present investigation is specific to only basic medium because the SS 316 electrode, which is economically viable and ecofriendly, can successfully be used under such conditions. Material and MethodsAll the used reagents NaOH, CHCOONa, KCl, nitrobenzamide etc, were of AR grade. The solutions were prepared in double distilled water. Cyclic voltammograms were obtained on fully computerized controlled Basic Electrochemistry system ECDA 001, using 3 electrode cell assembly with 1mm diameter glassy carbon as working electrode, Ag/AgCl as reference electrode and Pt wire as counter electrode. In aqueous media, 1.0mM concentration of reactant,1.0 M KCl used as supporting electrolyte to maintain the ionic strength of the solution and BR buffer used to maintain the desired pH viz 5, 7 and 9 were taken in 10 ml cell.Galvanostat designed and made by CDPE (Centre for Development of Physics Education, Univ. of Rajasthan, Jaipur) was used for carrying out controlled current electrolysis. For constant current electrolysis the conventional H-Cell has been used, stainless steel electrodes were used both as anode and cathode. All electrolysis process was carried out in buffer (1.0M CHCOONa + NaOH) and the pH of the solution was maintained constant at 9.00. After electrolysis the water was removed from the solution by distillation. The residue was then extracted with alcohol. The alcohol layer was allowed to evaporate. After evaporation product was isolated, purified and characterized by combined application of chromatographic techniques and spectroscopic methods. Results and Discussion Most cyclic voltammograms were recorded with an initial potential Ei of 1200 mV and switching potential Es of -1000 mV at different scan rates vlz. 50,100,200,300,400 and 500 mV/sec figure 1, 2, 3. -nitrobenzamide at scan rate of 50 mV/sec and pH 5, 7 and 9 appeared at -324 mV, -195mV and -328mV, respectively. As the sweep rate was gradually increased to 200,300, 400 and 500 mV/sec, peak gradually shifted towards higher values as is expected for an irreversible electron transfer processes. Table-1 summarizes the voltammetric data for -nitrobenzamide in basic medium. Constant values of Ipc/v1/2 and linear nature of Ipc vs. v1/2 plots indicates that the reduction of p-nitrobenzamide is a diffusion-controlled process. Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 3(3), 26-29, March (2013) Res. J. Chem. Sci. International Science Congress Association 27 Electrolytically reduced product 4,4’-dicarbamoylazobenzene was obtained in reasonably good yields(91.2%). Single spot TLC checked the purity of compounds. The identity of product was further confirmed on the basis of IR and NMR data have been given below in table 2. On the basis of kinetic parameter, number of total electrons change during reduction and product of bulk electrolysis the most probable mechanism for the reduction of -nitrobenzamide is given as scheme 1. Table-1 Current Potential measurement by cyclic voltammetry for - Nitro Benzamide Initial Potential Ei =1200 Mv, Working electrode: Glassy Carbon, Final Potential Es =-1000 mV, Reference electrode: Ag/AgCl, Auxillary electrode: Platinum S.N. pH ScanRate (mV\sec) Ep Ep/2 Ipc Ipc/v 1/2 Effect of scan rate Remark 1 5 50 -324 -269 210 29.7 Peak potential show cathodic shift of potential with increasing scan rates Irreversible 2 5 100 -341 -277 324 32.4 3 5 200 -372 -295 567 40.1 4 5 300 -378 -306 602 34.8 5 5 400 -394 -315 791 39.5 6 5 500 -399 -316 805 36.0 7 5 1000 -434 -349 1777 56.2 8 7 50 -195 -152 144 20.4 Peak potential shift towards negative side of potential with increasing scan rates Irreversible 9 7 100 -206 -164 238 23.8 10 7 200 -217 -173 416 29.4 11 7 300 -240 -191 567 32.7 12 7 400 -250 -197 653 32.6 13 7 500 -258 -213 727 32.5 14 7 1000 -292 -231 1447 45.7 15 9 50 -328 -293 176 24.8 With increasing scan rates potential shift towards negative side of potential Irreversible 16 9 100 -346 -304 259 25.9 17 9 300 -378 -325 514 29.6 18 9 400 -390 -336 677 33.8 19 9 500 -399 -554 904 40.4 Table-2 Characterization table for synthesis of 4,4’-dicarbamoyl azobenzene in basic medium Name of substrate IR Data (cm- 1 ) NMR Data (value) Compound Confirmed Yield (%) -Nitro Benzamide3099-3069 (Ar-H stretching) 3070s (C-H stretching) 3626,3293d (N-Hsym.stretch) 1682-1597 b (N-H bending) 1278-1228 s (C-N stretching) 1733 s (-C=O stretching) 882-829(m) -substitution) 1550-1450w (-N=N- group) 4.2 (4H) 6.5-8.5 (8H) 4,4’-Dicarbamoyl Azobenzene91.2 Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 3(3), 26-29, March (2013) Res. J. Chem. Sci. International Science Congress Association 28 CONHNO CONH NO e H2O 2OH CONH e NO CONH NO 2 H2O 2OH CONH NHOH CouplingCONH CONH N=N CONH CONH N=N 2e 2OH P r o p o s e d m e c h a n i s m i n b a s i c m e d i u m -nitrobenzamide4,4'-dicarbamoylazobenzene Scheme-1 -3000-2000-100010002000300040005000-1500-1000-50050010001500Potential (mV)Current (uA) Figure-1 Cyclic Voltammogram of -nitrobenzamide at different scan rates at pH 5 Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 3(3), 26-29, March (2013) Res. J. Chem. Sci. International Science Congress Association 29 -3000-2000-10001000200030004000-1500-1000-50050010001500Potential (mV)Cyrrent (uA) Figure-2 Cyclic Voltammogram of -nitrobenzamide at different scan rates at pH 7 -1500-1000-500500100015002000 2500 -1500-1000-50050010001500Potential (mV)Current (uA) Figure-3 Cyclic Voltammogram of -nitrobenzamide at different scan rates at pH 9 ConclusionThe reduction of p-nitrobenzamide was carried out galvanostatically at pH = 9.0 using Stainless (SS-316) as a working electrode and 4, 4’-dicarbamoylazobenzene was obtained in good yield (91.2%).References1.Shano T., Electro-organic Chemistry as a New Tool in Organic Synthesis, Springer, New York (1984)2.Torri S., Electro-Oraglanic Synthesis, Kodansha, Tokyo (1985)3.3.Singhal N., Sharma I.K. and Verma P.S., Trans. SAEST, 32, 77 (1997)4.Sangeeta Gupta, ph. D. Thesis, University of Rajasthan, Jaipur, India (1999)5.5..Singhal N., Sharma I.K. and Verma P.S., Electrochemical Reduction of -nitrophenol at Stainless Steel Electrodes, J.Electrochem.Soc, India,43(3) 203-204 (1998) 6.Gurjer V.S., Verma P.S, Mukherji S.K. and Tandon K.N., The Electrochemical Reduction of -Dinitrobenzene in Neutral and Basic Methanol-Water Medium at Stainless Steel (Type316) Cathode, Trans SAEST, 28, 145 (1993)7.Malik R., Sharma I.K. and Verma P.S, Electrochemical Reduction of -Nitro Toluene at Stainless Steel (SS316) Cathode in Basic Aqueous Methanol Medium, Bull.Electrochem., 15, 529-530 (1999)8.Yadav S.R, Goyal P., Sharma A., Verma P.S. and Sharma I.K., Electrochemical Reduction of Benzil and Salicylaldehyde at Stainless Steel Cathode in Basic Aqueous Methanol Medium, Indian Chem.Soc, 79, 695-607 (2002)9.9..Yadav S.R., Yadav R., Sharma A., Sharma I.K. and Verma P.S., Electrochemical Reduction of o-Amino Acetophenone at Stainless Steel Cathode in Basic Aqueous Methanol Medium, Bull.Electrochem,18(2), 87-90 (2002) 10.Sharma S.K.,Sharma I.K and P.S. Verma., Chemo Selective Reduction Of Aromatic Nitro Compounds to Aromatic Amines By Baker’s Yeast in Basic Solution,Int. J. Applied chemistry, 8(1), 1-4 (2012)