Intramolecular hydrogen bonding of o-hydroxyesters and related compounds evaluated by deuterium isotope effects on 13C chemical shifts and principal component analysis

o-Hydroxyaromatic esters, β-hydroxyketoesters, Meldrums acids, other o-hydroxyesters and a few o-hydroxyacid anhydrides are investigated by deuterium isotope effects on 13C chemical shifts, xΔC(OD). Especially the ester carbons show unusual deuterium isotope effects. A principal component analysis based on bond lengths and distances around the hydrogen bond six-membered ring make it possible to predict isotope effects. The ratio nΔCO(OD)/2ΔC(OD) can be used to predict the extent of transmission via the hydrogen bond. Furthermore, deuterium isotope effects can be used to gauge possible tautomerism.