Thermodynamic study of selected aromatic monoterpenoids

• Published in: Journal of molecular liquids Vol. 380; p. 121724
• Main Authors: Štejfa, Vojtěch, Fulem, Michal, Růžička, Květoslav
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.06.2023
• Subjects: Heat capacity; Ideal-gas thermodynamic properties; Monoterpenes; Vapor pressure; Vaporization and sublimation enthalpy; Heat capacity; Ideal-gas thermodynamic properties; Vaporization and sublimation enthalpy; Monoterpenes; Vapor pressure
• ISSN: 0167-7322; 1873-3166
• DOI: 10.1016/j.molliq.2023.121724

•Vapor pressures, heat capacities, and phase behavior of aromatic monoterpenoids were studied.•Ideal-gas thermodynamic properties were calculated using theoretical models.•Experimental data were compared to the scattered literature and treated with the simultaneous correlation method.•The physico-chemical data are interpreted from the view of molecular interactions. Thermodynamic properties of aromatic alcohols thymol, carvacrol, and cuminol were studied in this work as part of our effort to establish reliable physicochemical data for common monoterpenes. The phase behavior of the compounds was investigated by heat-flux differential scanning calorimetry (DSC) above 183 K with a special focus on the signs of polymorphic behavior. The heat capacities of the condensed phases were determined by a Tian-Calvet type calorimeter. Vapour pressure measurements were performed using two static apparatus over a wide temperature range, including environmentally important ambient temperatures. The conformational space of the compounds was examined using density functional theory (DFT) calculations, and the ideal-gas thermodynamic properties were subsequently calculated using statistical thermodynamics. A consistent thermodynamic description is presented, which was developed using the method of simultaneous correlation that processes experimental data on phase behavior, vapor pressures, and condensed phase heat capacities together with calculated ideal-gas heat capacities. The influence of the position of the hydroxyl group on the thermodynamic properties is discussed and rationalized.