Thermodynamic study of selected monoterpenes IV

• Published in: The Journal of chemical thermodynamics Vol. 144; p. 106013
• Main Authors: Štejfa, Vojtěch, Fulem, Michal, Růžička, Květoslav
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.05.2020
• Subjects: Heat capacity; Ideal-gas thermodynamic properties; Monoterpenes; Vapour pressure; Vapourization and sublimation enthalpy; Vapour pressure; Heat capacity; Ideal-gas thermodynamic properties; Vapourization and sublimation enthalpy; Monoterpenes
• ISSN: 0021-9614; 1096-3626
• DOI: 10.1016/j.jct.2019.106013

•Monocyclic monoterpenes (−)-menthone, (+)-pulegone, and (−)-isopulegol.•Calorimetric study of phase behaviour and heat capacities.•Vapour pressure measurements over a wide temperature range using two static apparatus.•Ideal-gas thermodynamic properties obtained by statistical thermodynamics.•Consistent thermodynamic description developed using the SimCor method. An extensive thermodynamic study of three monoterpenes, (−)-menthone, (+)-pulegone, and (−)-isopulegol, is presented in this work. Phase behaviour was investigated by a heat-flux differential scanning calorimetry (DSC) from 183 K resulting in detection of polymorphic behaviour of (−)-isopulegol and a noticeably slow crystallization of (+)-pulegone. Two static apparatus were employed for the vapour pressure measurements over a wide temperature range including environmentally important ambient temperatures. Heat capacities of liquid phase were measured by Tian-Calvet calorimetry at temperatures between 266 K and 353 K. Conformational space of the compounds was examined using the density functional theory (DFT) calculations and the ideal-gas thermodynamic properties were subsequently calculated using statistical thermodynamics. A consistent thermodynamic description was developed using the method of simultaneous correlation, where the experimental data for phase behaviour, vapour pressures, and condensed phase heat capacities and calculated ideal-gas heat capacities are treated together.