Single crystal, Hirshfeld surface and theoretical analysis of methyl 4-hydroxybenzoate, a common cosmetic, drug and food preservative-Experiment versus theory.

Abeer Sharfalddin,Bambar Davaasuren,Mariusz Jaremko,Abdul-Hamid Emwas,Łukasz Jaremko,Mostafa Hussien,Robert John O’Reilly

doi:10.1371/journal.pone.0239200

Abstract

Methyl 4-hydroxybenzoate, commonly known as methyl paraben, is an anti-microbial agent used in cosmetics and personal-care products, and as a food preservative. In this study, the single crystal X-ray structure of methyl 4-hydroxybenzoate was determined at 120 K. The crystal structure comprises three methyl 4-hydroxybenzoate molecules condensed to a 3D framework via extensive intermolecular hydrogen bonding. Hirshfeld surface analysis was performed to determine the intermolecular interactions and the crystal packing. In addition, computational calculations of methyl 4-hydroxybenzoate were obtained using the Gaussian 09W program, and by quantum mechanical methods, Hartree Fock (HF) and Density Functional Theory (DFT) with the 6–311G(d,p) basis set. The experimental FT-IR spectrum strongly correlated with the computed vibrational spectra (R2 = 0.995). The energies of the frontier orbitals, HOMO and LUMO, were used to calculate the chemical quantum parameters. The lower band gap value (ΔE) indicates the molecular determinants underlying the known pharmaceutical activity of the molecule.

Highlights

The polymorphic modifications of methyl 4-hydroxybenzoate, known as p-oxybenzoic acid methyl ester, were first reported in the 1930s [1, 2]
Gelbrich et al reported that the presence of Z’ = 3 phase is associated with the preference of local symmetry elements in the crystal structure [9]
Hirshfeld surface analysis is a quantitative way to study the intermolecular interactions of the molecules in a crystal structure

Summary

Introduction

The polymorphic modifications of methyl 4-hydroxybenzoate, known as p-oxybenzoic acid methyl ester, were first reported in the 1930s [1, 2]. Analysis of methyl 4-hydroxybenzoate a common cosmetics, drugs and foods preservative-experiment versus theory. We have numbered these modifications to distinguish four different modifications, which doesn’t completely match Lindpaintner’s report. The methyl 4-hydroxybenzoate molecules are connected through extensive O-H O hydrogen bonding-forming 1D chains. The main difference between the four polymorphs is the geometry of the formed 1D chains through H-bonding [8, 9]. Nath et al carried out 2D Hirshfeld surface analysis and IR- spectroscopic studies of polymorphs 1 and 2 to highlight the differences between the two modifications in terms of hydrogen bonding and aromatic interactions [8]. The lattice energy of all four polymorphs of methyl 4-hydroxybenzoate was calculated using various theoretical approaches and compared [9]

Methods

Results

Conclusion