Microsolvation of phenol in water: structures, hydration free energy and enthalpy

ABSTRACT

In this work, we have studied the microsolvation of phenol in water. We started by identifying initial configurations of phenol-water clusters using classical molecular dynamics. The configurations are optimised at the ωB97XD/aug-cc-pVDZ level of theory. To understand the interaction between phenol and the solvating water molecules, we performed a quantum theory of atoms in molecules (QTAIM) analysis. The results show that the structures of phenol-water clusters are similar to those of neutral water clusters. The QTAIM analysis shows that the structures of phenol-water clusters are stabilised by strong OH··· O hydrogen bondings, weak CH··· O hydrogen bondings, and OH$\cdots \pi$ bonding interactions. The located structures of phenol-water clusters have been used to calculate the absolute hydration free energy and enthalpy of phenol for temperatures between 20 and 400 K. The hydration energies are calculated using the cluster continuum solvation model. It has been found that the explicit solvation has negligible effects on the hydration free energy and enthalpy of phenol. Furthermore, the hydration free energy of phenol is found to be linearly varying with increasing temperature, while the hydration enthalpy is found to be temperature independent. The estimated hydration free energy of phenol is slightly underestimated as compared to a previously reported experimental estimate.

KEYWORDS:

• Solvation of phenol
• hydration free energy
• hydrogen bond network
• QTAIM analysis
• temperature effects

Acknowledgments

The authors are grateful to the Center for High Performance Computing (CHPC) in South Africa for granting them access to their clusters and computational resources. The Norwegian Supercomputing Program (UNINETT Sigma2, Grant No. NN9684K) is acknowledged for computer time. We would also like to thank the Central Research Fund of the University of the Free State.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data used in this work is provided in the manuscript or in the supporting information.

Additional information

Funding

This work was supported by the University of the Free State.