オルト効果(第4報)

置換安息香酸エチルの水中におけるアルカリ加水分解速度

抄録

In order to confirm the authors' view that in the dissociation of substituted benzoic acids, the ortho effect is markedly influenced by the type of solvent, whereas in the hydrolysis of their esters, the ortho effect is essentially unaffected, the rates of alkaline hydrolysis of o-, m-, and p-substituted ethyl benzoates were measured in 3 wt.% ethanol-water at 25°C The rate of reaction was calculated based on the changes in optical density at 220-290mμ. The reaction rate of thenon-substituted benzoate in 3 wt.% ethanol-water was approximately 50 times as much as that observed in 85 wt.% ethanol-water, and the Hammett's p value, 1/2. However, the ortho effects, log (k ortho/k para), remained almost unchanged. Possible reasons for these facts have been discussed in the light of the ortho effect observed in the dissociation of substituted benzoic acids.