Untersuchungen zur Hydrolysestabilität von 4-Arylmethyliden-2-pyrazolin-5-onen

Investigations on the Hydrolytic Stability of 4-Arylmethylidene-2-pyrazolin-5-ones The 4-Arylmethylidene-2-pyrazoline-5-ones S are not stable under aqueous alkaline conditions. By the substitution of R³ with electron donor substituents S reacts preferably yielding aldehyde A and 2-pyrazoline-5-one P , while with electron acceptor substituents S forms 4,4′-aryl-methylidene-bis-2-pyrazoline-5-one B . The intermediate of hydrolysis is 4-(arylhydroxymethyl)-2-pyrazoline-5-one SOH . The second order rate constants of the reaction of S with hydroxidions and with 2-pyrazoline-5-ones P ⁻ are determined. The dependence of the hydrolytic decomposition of S on the pH vaue substituents and temperature is suitable for the intermediate formation of SOH .