THE CYCLIZATION OF 2-SUBSTITUTED IMIDAZOLINES IN SULFURIC-ACID

A study of the rates of the cyclizations 1 --> 3 and 2 --> 4 as a func tion of medium acidity and temperature in aqueous sulfuric acid has be en performed. The latter reaction is five times faster at all aciditie s. An excess acidity kinetic analysis reveals the probable involvement of a water molecule in the reaction in both cases. Mechanistic possib ilities suggested by the observations are discussed; it is proposed th at the water molecule acts as a base catalyst during the rate-determin ing ring closure.