Pressure and temperature-dependent gauche-trans isomerization of 1-bromopropane: Raman measurement and statistical thermodynamic analysis

摘要

Raman measurements of the isomerization equilibrium in liquid 1-bromopropane are compared with perturbed hard-body fluid predications. The integrated areas of the Raman bands arising from the C-Br stretch of the gauche and trans conformations are used to track the isomerization equilibrium as a function of pressure and temperature. Repulsive solvent-solute interactions are treated using the recently developed excluded-volume-anisotropy model (based on realistic molecular structures for the two isomers and the equation of state of liquid 1-bromopropane), and cohesive interactions are treated using the van der Waals mean field approximation. The results illustrate the delicate balance of attractive and repulsive solute-solvent interactions which underlie the effects of solvation on chemical equilibria. Comparison of the measured and predicated changes in #DELTA#H with pressure, and #DELTA#V with temperature, are used to determine parameters describing the attractive mean field and cavity formation energies of the two isomers, as well as the isomerization enthalpy and entropy of the isolated molecule.