In this work the effect of functional groups (substuents) on the reduction potentials of carbonyl group containing pesticides topramezone ,fenomidone and methiocarb were studied. Deferential pulse adsorptive stripping voltammetry, cyclic voltammetry, millicoulometry and controlled potential electrolysis were used for the determination of reduction potentials and electrode mechanisms. HMDE (Hanging mercury drop electrode) used as working electrode and universal buffer used as supporting electrolyte.