Micellar Effect on The Reaction of Acetophenone with Phenylhydrazine

Abstract

The kinetics of acetophenone-phenylhydrazine reaction has been studied spectrophotometrically in the presence of anionic surfactant, sodium lauryl sulphate (NaLS), cationic surfactant, cetyl trimethyl ammonium bromide (CTAB) and non-ionic surfactants, polyethylene glycols of different molecular weights (PEG 4000, PEG 6000 and PEG 20000) at 30 ºC. All the above surfactants accelerated the reaction at low concentration, reaching a rate maximum and inhibiting the reaction at postmicellar concentrations. On the basis of kinetic results, it can be inferred that at low concentrations, NaLS and CTAB act as simple electrolytes changing polarity of the medium and in the case of polyethylene glycols, the polarity of N–H bond changes when phenylhydrazine is embedded on to the polyethylene glycol matrix. A plausible mechanism is drawn based on these observations.