Effects of Pressure and Temperature on the Dynamics of Liquid tert-Butyl Alcohol

Abstract

The solution structure of tert-butyl alcohol was investigated as a function of pressure and temperature using high-resolution nuclear magnetic resonance (NMR) spectroscopy. Simulations of the solution structure were undertaken using molecular dynamics and a simple phenomenological model describing clustering in liquid tert-butyl alcohol. Chemical shifts, relaxation times (T1), and line widths (fwhm) of the CH3 and OH groups were monitored over a pressure and temperature range up to ∼1.0 kbar and from 297 to 423 K, respectively. Simulations demonstrated a cyclic tetramer as the dominant structure in the liquid, with pressure having negligible effects on the overall liquid structure. Temperature shifted the structural distribution and increased the mole fraction of short linear chains in liquid tert-butyl alcohol. The rotational correlation time determined from the spin−lattice relaxation time, T1, and its pressure dependence is consistent with a cyclic structure for liquid tert-butyl alcohol that is stable as a function of pressure. This is in contrast to earlier studies of methanol in which pressure was determined to decrease hydrogen bonding and linear chain structures were predominant in the liquid.