Cavity formation and dipolar contribution to the gauche-trans isomerization of 1-chloropropane and 1,2-dichloroethane

The effects of pressure and temperature on the gauche-trans conformational equilibrium of 1-chloropropane and 1,2-dichloroethane dissolved in diethyl ether (ethoxyethane) are measured using Raman spectroscopy and analyzed usi ng thermodynamic perturbation theory. The effects of solvation on the isome rization equilibrium, monitored using the C-Cl stretch band intensities of the two conformers, are interpreted as a sum of intermolecular attractive a nd repulsive solute-solvent interactions. A perturbative analysis of the is omerization enthalpy, DeltaH, and volume, DeltaV, is used to extract repuls ive cavity formation and attractive mean field solvation contributions to t he conformational equilibrium. Comparison of the thermodynamics of the two solutes with each other, and with previous gas phase and solution results, are used to confirm the self-consistency of the perturbative modeling strat egy and to quantify dipolar contributions to the gauche-trans isomerization process.