Publications [#233094] of Richard MacPhail
Journal Articles
- MacPhail, RA; Monroe, FC, "Frequency-dependent solvent friction and torsional damping in liquid 1,2-difluoroethane", Chemical PhysicsApril,, 1991, 152(1-2), 93-105, Elsevier BV (Invited article for special issue
on "Friction in Liquid Phase Reactions".) [doi].
(last updated on 2024/04/17)Abstract:
We have used Raman spectroscopy to study the torsional dynamics, rotational dynamics, and conformational solvation energy of liquid 1,2-difluoroethane. From the Raman intensities, we obtain ΔH(g-t) = -2.4±0.1 kcal/mol, indicating strong dipolar solvation of the gauche conformer. We analyze the Raman linewidths of the CCF bending bands to obtain the zero-frequency torsional damping coefficient or well friction for the gauche conformer, and from the linewidth of the torsion band we obtain the friction evaluated at the torsional frequency. The zero-frequency well friction shows deviations from hydrodynamic behavior reminiscent of those observed for barrier friction, whereas the high-frequency friction is considerably smaller in magnitude and independent of temperature and viscosity. The zero-frequency torsional friction correlates linearly with the rotational friction. It is argued that the small amplitude of the torsional fluctuations emphasizes the short distance, or high wavevector components of the solvent friction. Dielectric friction apparently does not contribute to the torsional friction at the observed frequencies. © 1991.