Alkaline hydrolysis of cephaloridine: an 1H - NMR study. Temperature dependence of the rate constants

Article abstract of DOI:10.1002/kin.550251007

A kinetic study on the basic hydrolysis of cephaloridine at pD = 10.5 was carried out by using the ¹H - NMR technique. Epimerization at H₇, a nucleophilic attack of hydroxyl ion on the β-lactam carbonyl group followed by the release of the pyridine molecule, and isomerization of the double bond at position 3 in the dihydrothiazine ring were the major reactions observed. Based on the results obtained, it should be emphasized that the presence of a pyridine group at 3′ results in a slightly increased formation constant for the exo methylene compound relative to other cephalosporins with different substituents at that position. The activation energy for the epimerization constant and the cleavage of the β-lactam ring at pD 10.5 was 21.2 kcal/mol