Unsaturated hydantoin derivatives. 19. Effect of temperature on the rate of alkaline hydrolysis of 2-thioxo-5-arylidenehydantoins and some of their derivatives

The effect of temperature on the rate of alkaline hydrolysis of the monoanions of 2-thioxo-5-arylidenehydantoins was studied. The investigated series obeys an isokinetic law with isokinetic temperature β=321±10°K. The kinetic data obtained constitute evidence that the mechanisms of the hydrolysis of 2-thioxo-5-arylidenehydantoins and their oxygen analogs are identical. A change in the solvation of the starting and transition states is the principal reason for the change in the reactivities of 5-arylidene-2-thioxohydantoins under the influence of the substituent and the temperature as compared with 5-arylidenehydantoins, the N- and Smethyl derivatives, and 4-thioxo-5-benzylidenehydantoin.