Ring closure of hydantoic acids to hydantoins studied under aqueous acid conditions in the pH range 0-2 at 50" shows a specific acid-catalyzed component at low pH as well as a spontaneous component at higher pH. The accelerating effect of substitution on the 2 carbon of hydantoic acids by alkyl or aryl groups is not always as large as can be expected on the basis of their bulk. The observed rates appear to be rationalizable, however, in terms of a ...
