The kinetics of hydrolysis of AMX-benzylidene)aniline, with × = OH or OCH3 in the ortho, meta, or para position. have been investigated in the pH range from -1 to 14 at 30 °C by means of ultraviolet spectrophotometry. The mechanism of hydrolysis of these Schiff bases was found to be critically dependent on the presence of the ketoamine tautomer in some of these compounds, as was the case for the Schiff bases derived from isopropylamine.1 The tautomeric constants have been estimated by various methods and consistent results have been obtained when comparison was possible. © 1979, American Chemical Society. All rights reserved.