Intramolecular hydrogen bonding and molecular conformation. Part 4.—Corrections of thermodynamic properties obtained by IR measurements at different temperatures and pressures

Abstract

Corrections have been examined for infrared measurements of the enthalpy change, ΔH, and the partial molar volume change, ΔV, for the rupture of an intramolecular hydrogen bond of some hydroxyketones and o-halophenols in dilute solutions. Expressions of ΔH and ΔV were given by allowing for the temperature and pressure dependences of these quantities, and the molar integrated intensities. The temperature and pressure coefficients of the molar integrated intensities were assumed to be given by experimental values of model compounds which are similar to the molecules concerned, but which do not exhibit conformational equilibrium. It has been found that the corrections are not small enough to be negligible, compared with the values obtained by the usual procedures.