Infrared studies of terpenoid compounds. Part IV. Correlation of acidity and intramolecular hydrogen bonding for γ-hydroxy carboxylic acids

Abstract

Infrared absorptions in the hydroxyl and carbonyl regions of 6-hydroxy-podocarpic and marrubiic acids, the corresponding methyl esters, and related compounds have been measured. The extent of the intramolecular –OH ⋯ O[graphic omitted]C–O– and –OH ⋯ [graphic omitted]O–[graphic omitted]CO hydrogen bonding which involves the 6-hydroxyl and 4-carboxylate groups correlates with the pK*_MCS values for the acids.