Abstract
Rate constants for oxygen-base-catalyzed enolization of di- and tricarbonyl compounds can be correlated by a Marcus equation, with hydroxide requiring a slightly different curve from other oxyanions. Data for monocarbonyl compounds fall on a slightly different, but similar, set of curves. The equilibrium constants for enolization for a set of monocarbonyl compounds were derived from recent work in this laboratory. These correlations permit estimation of pKaKeto for a number of other monocarbonyl compounds from kinetics data in the literature. Elaboration of methods previously developed permits estimation of pKaEnol. From the values of pKaEnol and pKaKeto, pKEnol can be derived. It is pointed out that pKaKeto for acetone and acetophenone can be determined from the kinetics of the reaction with hypochlorite in base; the values so derived are in good agreement with those used in this work. pKEnol values are reported for: 1,3-dichloroacetone, 2.0; 1,1-dichloroacetone, 4.9; ethyl pyruvate, 4.2; bromoacetone, 3.5; chloroacetone, 3.7; l-phenyl-2-propanone, 4.5 (CH2); 7.2 (CH3); p-nitroacetophenone, 7.1; ethyl levulinate, 5.6; methoxyacetone, 6.9 (CH2); 7.6 (CH3); benzalacetone, 7.6; p-methoxyacetophenone, 7.8; 3-methyl-2-butanone, 8.0 (CH); 2,4-dimethyl-3-pentanone, 9.4.
Publisher
Canadian Science Publishing
Subject
Organic Chemistry,General Chemistry,Catalysis
Cited by
103 articles.
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