93214-75-6Relevant articles and documents
INVESTIGATION OF THE MECHANISMS OF FORMATION OF HETEROCYCLES BY NMR SPECTROSCOPY. III. THE EFFECT OF ELECTRONIC FACTORS ON THE KINETICS OF THE DEHYDRATION OF DIHYDROXYPYRAZOLIDINES AND HYDROXYPYRAZOLINES- THE INTERMEDIATES IN THE REACTION OF HYDRAZINE WITH 1,3-DIKETONES
Selivanov, S. I.,Golodova, K. G.,Abbasov, Ya. A.,Ershov, B. A.
, p. 1361 - 1364 (2007/10/02)
The rate constants for the dehydration of the dihydroxypyrazolidine and hydroxypyrazoline intermediates in the reaction of hydrazine with substituted benzoylacetones p-XC6H4COCH2COCH3 (X= CH3O, CH3, H, Cl, NO2) in methanol were determined by NMR spectroscopy using the stopped-flow technique.Increase in the electronegativity of the substituent leads, on the one hand, to an increase in the contribution from the reaction path involving the formation of the tautomeric pyrazoles with the participation of 3-methyl-5-(p-XC6H4)-5-hydroxypyrazoline and, on the other hand, to an increase in the rate of its conversion into the corresponding pyrazole.Analysis of the relationships between the dehydration rates and the Hammett ? constants confirms a reaction mechanism with the participation of the cyclic dihydroxypyrazolidine intermediate.
