The basicities of several 2′-, 3′-, and 4′-substituted 4-acetylbiphenyls and biphenyl-4-carboxylic acids have been determined spectrophotometrically in sulphuric acid media at 30°C. The pKBH+ of 3′- and 4′-substituted compounds are correlated by the Hammett equation. The 4′-methoxy group deviates considerably in the Hammett plot. This is attributed to its conjugative interaction with the carbonyl or carboxyl group aided by protonation. Good correlation exists between pKBH+ and σ+. The basicities of 2′-substituted 4-acetylbiphenyls and biphenyl-4-carboxylic acids reaffirm the existence of π-electron steric effect of 2′substituents.
Volume 134, 2022
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