Hydrolysis Velocity of Ketimines - Steric Hindrance Effect

Additional work has been carried on to gain further information concerning the significance of ortho-substituted groups upon the rate of which diphenyl ketimine hydrochlorides hydrolyze to ketones. In this particular study the following isomeric ketimines have been prepared and their hydrolysis velocities determined: 2, 6-dimethyl-, 2, 5-dimethyl-, 2, 4-dimethyl-, and 3, 5-dimethyldiphenyl ketimines hydrochlorides. The first of these with the two ortho-substituted methyl groups is hydrolyzed appreciably only after prolonged boiling with water. The last with no ortho-substituent is hydrolyzed very rapidly at room temperature, so that its reaction velocity must be measured at 0°C. The second and third ketimine salts, each having one ortho-substituted methyl, are hydrolyzed at a moderate rate at 25°