Hydrolysis of Electrophilic Olefins. I. Kinetic Studies on the Hydrolysis of p-Dimethylaminobenzylidene Derivatives of Active Methylene Compounds

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The dissociation constants (K_a) of the conjugate acids of the p-dimethylaminobenzylidene derivatives (I) of various active methylene compounds (XYCH_2) were determined. Alkaline hydrolysis of I was studied kinetically in 30% (v/v) ethanol at 25℃. The rates of nucleophilic attack of a hydroxide ion on the carbon-carbon double bonds of I were linearly correlated with the corresponding pK_a values. Thus the pK_a values are suggested to be useful parameters to evaluate the relative activating ability of the X and Y groups to support the attack of nucleophiles on compounds of the type XYC=CHAr. In the hydrolysis of structurally similar compounds α-(substituted benzoyl)-p-dimethyl-aminocinnamonitriles, the rates of carbon-carbon bond fission of an uncharged addition intermediate and those of carbon-carbon double bond formation from a carbanion intermediate were also correlated with the dissociation constants (K^<AM>_a) of the corresponding substituted benzoylacetonitriles. The pH-rate profile and the relationship between rates and K_a (or K^<AM>_a) suggested that the carbon-carbon bond fission of the uncharged intermediate is the rate-determining step in the alkaline hydrolysis of I.
公益社団法人日本薬学会の論文
1981-10-25