SOLVOLYSIS, EXCHANGE, AND ISOMERIZATION OF 4,4'-DIMETHYLBENZHYDRYL THIOCYANATE IN 95-PERCENT AQUEOUS ACETONE

In 95% aqueous acetone 4,4-dimethylbenzhydryl thiocyanate solvolyzes while it isomerizes. The solvolytic reaction displays common ion rate depression indicating that free carbonium ion intermediates are captured by the solvent. An analysis of the solvolytic and isotopic exchange rates, ks and kex, with changing the concentration of the added common ion, SCN−, shows that the sum k5 + kex remains constant and equal to the undepressed solvolytic rate, ks°. This finding demonstrates that the free carbonium ion is the only important intermediate involved both in the exchange and in the solvolysis process. The isomerization reaction is but slightly affected by the concentration of the common ion and appears to occur largely at a less advanced ionization stage, probably an intimate ion pair. © 1969, American Chemical Society. All rights reserved.