The Peculiar H-Bonding Network of 4-Methylcatechol: A Coupled Diffraction and In Silico Study

Area of Science:

• Crystallography
• Materials Science
• Organic Chemistry

Background:

• The crystal structure of 4-methylcatechol (4MEC) remained unsolved despite its simple formula (C7O2H8) and potential applications.
• Understanding molecular structure is crucial for predicting and utilizing material properties.

Purpose of the Study:

• To determine the crystal structure of 4-methylcatechol (4MEC).
• To investigate the role of the methyl group in influencing crystal packing and growth.
• To explain the difficulties encountered in obtaining single crystals of 4MEC.

Main Methods:

• X-ray powder diffraction (XRPD) was employed to gather structural data.
• First-principle calculations were utilized to accurately locate hydrogen atoms.
• Hirshfeld analysis was performed to assess the reliability of the solved structure and analyze intermolecular interactions.

Main Results:

• The crystal structure of 4MEC was successfully solved, revealing two molecules in the asymmetric unit.
• A peculiar hydrogen bond network featuring hydroxyl nests within octagonal frameworks was identified.
• Strong intermolecular interactions and significant inter-crystalline aggregation, leading to spherical aggregates, were observed.
• The methyl group was identified as the cause of these unique features, contrasting with the layered packing of catechol.

Conclusions:

• The solved crystal structure of 4MEC provides critical insights into its molecular arrangement.
• The unique packing and aggregation phenomena are attributed to the methyl substituent.
• The findings explain the challenges in obtaining single crystals, hindering traditional structural analysis.