The transmission of polar effects. Part XII. Confirmation of reversed dipolar substituent effects

A study of the hydroxyl- and carbonyl-stretching frequencies of a number of 8-substituted 1-naphthoic, cis- and trans-ortho-substituted cinnamic acids, and their methyl esters has been made. These results confirm the occurrence of reversed dipolar substituent effects in these systems. The pKa values of a series of cis- and trans-ortho-substituted cinnamic acids have been measured in 80% 2-methoxyethanol–water at 25°. These extend our observations of reversed dipolar substituent effects. The conformations of the cis-acids are discussed.