Solvent effect on isatin ring opening by alkaline hydrolysis

ABSTRACT

Hydrolysis of isatin by sodium hydroxide was followed spectrophotometrically in 0, 10, 20, 30, 40, 50, 60 and 70% [v/v] t- butanol-water mixtures and at various temperatures [30-45C]. Addition of a small amount of the organic solvent to water decreased largely the ring opening process. No linearity was observed for the plot of log k versus 1/D, or for the variation of delta E* with X2. The change in delta H* and delta S* with X2 showed maxima at the region where solvent structure changed. The isokinetic temperature [433K] indicated that the process was controlled by delta S* and not delta H*