Polymorphism and thermophysical properties of L- and DL-menthol

Published

November 5, 2018

Author(s)

Vojtech Stejfa, Ala Bazyleva, Michal Fulem, Jan Rohlicek, Eliska Skorepova, Kvetoslav Ruzicka, Andrey V. Blokhin

Abstract

The thermodynamic properties, phase behavior, and kinetics of polymorph transformations of racemic (DL-) and enantiopure (L-) menthol were studied using a combination of advanced experimental techniques, including static vapor pressure measurements, adiabatic calorimetry, Tian-Calvet calorimetry, differential scanning calorimetry (DSC), and variable-temperature X- ray powder diffraction. Several concomitant polymorphs (alpha, beta, gamma, and delta forms) were observed and studied. A continuous transformation to the stable alpha-form was detected by DSC and in detail monitored using the X-ray powder diffraction. A long-term coexistence of the stable crystalline form with liquid phase was observed. The vapor pressure measurements of both compounds were performed using two static apparatus over a temperature range from 274 to 363 K. Condensed-phase heat capacities were measured by adiabatic and Tian-Calvet calorimetry in the wide temperature interval from 5 to 368 K. Experimental data of L- and DL-menthol are compared mutually as well as with available literature results. The thermodynamic functions of crystalline and liquid L-menthol between 0 K and 370 K were calculated from the calorimetric results. The thermodynamic properties in the ideal-gas state were obtained by combining statistical thermodynamics and quantum chemical calculations based on thorough conformational analysis. Calculated ideal-gas heat capacities and experimental data on vapor pressure and condensed-phase heat capacity were treated simultaneously to obtain a consistent thermodynamic description. Based on the obtained results, phase diagrams of L-menthol and DL-menthol were suggested.

Citation

Journal of Chemical Thermodynamics

Volume

131

Pub Type

Journals

Download Paper

https://doi.org/10.1016/j.jct.2018.11.004

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Keywords

monoterpenoids, menthol, vapor pressure, heat capacity, variable-temperature XRPD, thermodynamic properties, ideal gas, statistical thermodynamics

Citation

Stejfa, V. , Bazyleva, A. , Fulem, M. , Rohlicek, J. , Skorepova, E. , Ruzicka, K. and Blokhin, A. (2018), Polymorphism and thermophysical properties of L- and DL-menthol, Journal of Chemical Thermodynamics, [online], https://doi.org/10.1016/j.jct.2018.11.004, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=926687 (Accessed October 14, 2025)