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 (T 1), 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, T 1, 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.

Does High Pressure Induce Structural Reorganization in Linear Alcohols? A Computational Answer

“…Only few works deal with the effect of pressure on alcohols, most of which concern methanol and its crystalline structure at high pressure . Yonker et al . have reported a rich multimer bulk composition of ring‐like conformers for tert ‐butanol at 600 bar.…”

“…Only few works deal with the effect of pressureo na lcohols, most of which concern methanol and its crystalline structure at high pressure. [12][13][14][15] Yonker et al [16] have reported ar ich multimer bulk composition of ring-like conformers for tert-butanol at 600 bar.S uch folded structures were also observed by Ridout et al [17] in the crystalline structure of isopropanol at 11.2 kbar.P awlus et al, [18][19][20] and later Fragiadakis et al, [21] have workedo nt he relaxation processeso fs ome monohydroxy alcohols, which suggestsa no verall reorganization of the hydrogen-bond network at pressures highert han 5.5 kbar;t his threshold was also reported by Petravic et al [22] for ethanol. Although the systemsa ppear to be almost unaffected by pressures below this value, once above the situation changes dramatically,w ith ad iscontinuity.O no et al [23] made ar emarkable report on density and viscosity trends as af unction of pressure for the three shortestl inear alcohols.…”

The Structures of ZnCl2-Ethanol Mixtures, a Spectroscopic and Quantum Chemical Calculation Study

“…The H-bonded networks in alcohols are readily susceptible to disruption and reformation by chemical perturbations [ 9 , 10 , 11 ]. Structural properties of alcohols in pure state or mixed with cosolvents and their relationship with H-bonds have been the subject of numerous experimental and computational studies [ 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ]. When it comes to electrolytes, their solvation in alcohols and aqueous alcohol solutions are of great significance in many industrial and natural processes [ 22 , 23 , 24 ].…”

The Structure of Liquid Methanol

“…[13][14][15][16][17][18][19][20][21][22] This view is also supported by molecular dynamics (MD) simulation studies, [23][24][25][26][27][28] which predict, mainly, open chains consisting of 2-6 molecules for methanol and ethanol. However, for tert-butyl alcohol, Yonker et al [29] found evidence for a cyclic structure (mainly composed of tetramers). In MD studies the liquid interactions are approximated with empirical potential functions of pairwise-additive form, whereas ab initio calculations and recent molecular cluster studies showed the importance of non-pairwise-additive cooperative interactions for condensation phenomena.…”