(382p) Prediction of Vapor-Liquid Coexistence for Carvacrol Using Equation of State Methods and Monte Carlo Simulations

Carvacrol (IUPAC name: 2-methyl-5-(propan-2-yl)phenol) is a natural product mainly extracted from plants of the Origanum genus and is also an important component of the essential oil derived from thyme. Carvacrol has anti-bacterial (demonstrated to be effective against various species of pathogenic bacteria including Escherichia coli and Salmonella) as well as anti-cancer properties. [1] Isolation of natural products requires vast amounts of raw materials and solvents, energy and water for extremely low yields.[2] Hence, a molecular simulation-based approach is not only a cost-effective alternative to performing experiments but it also simultaneously provides us with insights into the molecular level behavior which manifests in the observed macroscopic phenomena.

The knowledge of the pure component VLE properties is essential for its efficient extraction. However, the only experimental data reported in literature are at low vapor pressures (within 1 atm) and the normal boiling point is reported to be ~510 K. [3] The enthalpy of vaporization data is only available at 298.15 K. [4] In this study, we report the VLE data obtained from theory using Equations of State (EoS) and a molecular simulation technique – Gibbs Ensemble Monte Carlo (GEMC) [5]. In the EoS methods (which are extensively employed in process simulation software), we have used three equations: Soave-Redlich-Kwong , Peng-Robinson and volume translated Peng-Robinson . These EoS require the critical properties and the acentric factor of the compound as inputs. These inputs can be estimated in two ways: using (1) Group Contribution methods such as Joback-Reid [6] and Marrero-Gani (MG) [7]; and (2) molecular simulation approach. GC is quick though inherently approximate whereas molecular simulation is a fundamental approach which allows study of the phase behavior from a description of the interactions between the molecules. The interactions present in this system have been modeled according to the TraPPE-UA (Transferrable Potentials for Phase Equilibria-United Atom) force field. [8] Parameters for interactions involving the phenolic -OH group are not reported in the relevant TraPPE-UA literature. These parameters are adopted from a study on curcumin, using OPLS-UA (Optimized Potential for Liquid Simulations – United Atom) force field. [9] The simulations are performed using MCCCS Towhee package in the temperature range from 500 K to 650 K. [10] The structure of the liquid phase has been studied by computing the intermolecular radial distribution functions, which also allow us to determine the extent of hydrogen bonding present.

References:

[1] Sharifi-Rad M, et al., Phytotherapy Research, 2018; 32, 1675–1687

[2] Farid Chemat, et al., Int. J. Mol. Sci., 2012; 13, 8615-8627

[3] Stull, Daniel R., et al., Ind. Eng. Chem., 1947;39 (4) 517-540

[4] van Roon, et al., Journal of Chromatography A, 2002; 955 (1) 105-115

[5] A. Z. Panagiotopoulos, Molecular Physics, 1987; 61, 813-826

[6] Joback K.G., et al., Chem. Eng. Commun., 1987; 57, 233–243

[7] J. Marrero and R. Gani, Fluid Phase Equilibria, 2001; 183–184,183–208

[8] Eggimann, et al. Molec. Simul. 2014, 40, 101-105

[9] T. Patsahan et al., Condensed Matter Physics 2017; 20 (2) 23003

[10] MCCCS Towhee. Available at: http://towhee.sourceforge.net. Accessed in January, 2019