Separating Enthalpy and Volume Contributions in Photothermal Experiments: A Perspective

Abstract

Abstract— Signals in photothermal experiments originate from both enthalpies and volumes of reaction. Two methods have been reported through which enthalpy and volume contributions can be separated: (1) analysis of signals as a function of temperature in aqueous solution or (2) analysis of signals from a series of linear alkanes or solvent mixtures. This manuscript describes potential difficulties in the application of the latter method to charge transfer reactions and proposes two alternative approaches by which the separation might be effected in a single organic solvent: (a) measurement of signals in isotopomeric solvents or (b) measurement of thermally induced changes in refractive index under conditions of constant density. The utility of neither approach has been demonstrated in any solvent other than water.