Abstract
The synthesis and hydrolysis study in boiling 6.04N hydrochloric acid of lactams have been extended to include 1-benzyl-2-pyrrolidinone (I), 1-benzyl-2-oxo-5-piperidineacetic acid (II), 1-benzyl-2-oxo-4-piperidinecarboxylic acid (III), and 1-benzyl-2-oxo-5-piperidinecarboxylic acid (IV). In all cases, the hydrolysis was found to proceed to an equilibrium as shown in Table III. Substituents at the 4- or 5-position of the 2-piperidone ring seemed to favor the lactam form in the lactam-ω-amino acid hydrochloride equilibrium. The lactam form was somewhat more favored in the case of the simple 5-membered lactam (I) than in the case of the simple 6-membered lactam, 1-benzyl-2-piperidone. Such a trend was more evident in the cases of II and III ; the 5- and 6-membered lactams were equilibrated in the ratio 4.5 : 1. It was also observed that III was thermally converted into the 5-membered lactam (XV), whereas II was stable at 180°for 5hr. Infrared frequency data on several lactams are collected in Table I in order to visualize the lower shift of lactam vco exhibited in the solid state by the lactams possessing the carboxyl group else where in the molecule.
