Electrometric studies on the reduction of the azomethine bond in schiff bases and the effect of substituent on it

1037-1041The peak potential (Ep) of benzaldehyde (Bz) and its schiff bases with aniline, 3- and 4-OH-, 4-OCH3-' 4-Cl- and 4-NO2-anilines in CH3OH are determined at HMDE employing voltammetric techniques. The results are discussed in terms of influence of the substituent on phenylimino ring affecting electrochemical behaviour of - CH = N - bond. The shift in Ep values of schiff bases is examined on the basis of effect of substituent with respect to Bz (Ep') and with parent benzylidene-aniline (1) (Ep”). It is found that - CH = N - reduction step involved transfer of two electrons and the reduction process is diffusion controlled and irreversible. The kinetic parameters have been evaluated and used to calculate Hammett constant (σx) The characteristic potentials (Ep”) versus σx plot has shown linear relationship and the reaction constant, rho (pπ, - CH = N -), has been determined from the slope value. The positive value of pπ, - CH = N - indicates the nucleophilic nature of the electrode process. The CPC experiments have shown that in the reduction process of the studied schiff bases except benzylidene-4'-nitroaniline, where there is a transfer of six electrons, there is transfer of two electrons. The reduction products after CPC experiments have been characterised by the chemical tests and the spectral studies (UV and IR). A reduction mechanism is proposed on the basis of voltammetric measurements and product analysis