M. Coll et al., AB-INITIO STUDY OF THE BASIC HYDROLYSIS OF THE PYRAZOLIDINONE RING, The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory, 102(29), 1998, pp. 5915-5922
A complete study of basic hydrolysis of the pyrazolidinone ring by ab
initio calculations at RHF/6-31+G// RHF/6-31+G* and MP2/6-31+G*//MP2/
6-31+G has been carried out. The alkaline hydrolysis has been studied
through a B-AC2 mechanism, characterized by a nucleophilic attack of
the hydroxyl group on the carbonyl of the gamma-lactam ring, formation
of the tetrahedral intermediate, and cleavage of the C2N3 bond to yie
ld the final reaction product. In the gas phase, the interaction of OH
- with the carbonyl carbon to form a tetrahedral intermediate takes pl
ace without any barrier height. Two possible mechanisms have been cons
idered for the transfer of the hydroxyl hydrogen to the nitrogen of th
e gamma-lactam: a stepwise mechanism involving the cleavage of the C2N
3 bond and subsequent transfer of the hydrogen to the gamma-lactam nit
rogen and st concerted mechanism. The MP2/6-31+G//MP2/6-31+G* barrier
heights are 32.72 and 25.64 kcal/mol, respectively. The elimination r
eaction, which in the gas phase may interfere with the nucleophilic at
tack, has also been studied.