オルト効果(第6報) : 置換オルト・トリル酸エチルのアルカリ加水分解におけるオルト効果の置換基効果

概要

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Like ethyl benzoates, the alkaline hydrolysis of 2-methyl substituted ethyl benzoates in 85% ethanol-water at 25°C followed the Hammett rule, though the ρ value increased from 2.50 to 2.76 due to the presence of the ortho-methyl group . Under the same conditions, the ρ value for the ionizations of substituted anilines was 3.34, which is considerably higher than 2.77 observed in water . The 4- or 5-substituent effects on the ortho effect in the alkaline hydrolysis of ethyl 2-methylbenzoates have been discussed based on the substituent effects in the original systems as well as in the product systems . Though marked differences were noted between the ortho effect in the dissociation of various benzoic acids and that in the hydrolysis of their esters, the substituent effects on the ortho effect were alike. If the ester group in the transition state is treated as a substituent, the .D value (-0.09--0. 17) is found to be on the considerably negative side from σm-CO<SUB>2</SUB><SUP>θ</SUP>. The carbonyl character may thus be masked to a considerable extent in the transition state.
社団法人有機合成化学協会の論文