Vapour–liquid coexistence of carvacrol: a molecular simulation study

Abstract

Carvacrol, a naturally occurring aromatic compound, is known to have medicinal properties. However, the experimental vapour–liquid equilibria (VLE) data reported in literature are limited to vapour pressures up to the normal boiling point and heats of vapourization at three relatively low temperatures. As knowledge of VLE data is essential for the design of efficient separation processes, a molecular simulation technique is employed in conjunction with a force field (where the potential functions and parameters have been obtained entirely from literature) to predict the coexistence properties, including densities, at elevated temperatures. Process simulation software employed to design separation processes generally employ the equation of state approach which requires as input the critical state properties and acentric factor (which are not reported in literature for carvacrol) and are determined to be Tc = 7065 K, Pc = 333 bar, Vc = 50316 cc/mol and ω = 0.485 in this work. The numbers in subscript indicate the uncertainties in the last digit(s). Additionally, the structure of the coexisting liquid phase has also been investigated at the molecular level using the intermolecular site-site radial distribution functions and number integrals to determine the extent of hydrogen-bonding.