Tramadol hydro-chloride-benzoic acid (1/1)

Area of Science:

• Crystallography
• Supramolecular Chemistry
• Organic Chemistry

Background:

• Co-crystal salts offer unique structural and functional properties.
• Understanding intermolecular interactions is key to designing new materials.
• The specific compound investigated presents an opportunity to study novel bonding arrangements.

Purpose of the Study:

• To elucidate the crystal structure of the title co-crystal salt: [2-hydroxy-2-(3-meth-oxy-phen-yl)cyclo-hexyl-meth-yl]dimethyl-aza-nium chloride-benzoic acid (1/1).
• To analyze the conformation of the cyclohexane ring and the orientation of aromatic rings.
• To investigate the intermolecular interactions stabilizing the crystal lattice.

Main Methods:

• Single-crystal X-ray diffraction was employed to determine the molecular and crystal structure.
• Analysis of bond lengths, bond angles, and dihedral angles provided conformational insights.
• Intermolecular interactions such as hydrogen bonding and C-H···π interactions were identified and characterized.

Main Results:

• The N atom in the ammonium cation is protonated, and the cyclohexane ring adopts a distorted chair conformation.
• A dihedral angle of 75.5(9)° was observed between the mean planes of the benzene rings in the cation and the benzoic acid molecule.
• Crystal packing is stabilized by O-H⋯Cl, N-H⋯Cl, and C-H⋯π interactions, forming a 2D chain network along the b axis.
• The benzoic acid molecule participates in mutual hydrogen bonding with the chloride anion, deviating from typical dimer formation.

Conclusions:

• The study successfully characterized the crystal structure of the novel co-crystal salt.
• The observed intermolecular interactions, including hydrogen bonding and π-π stacking, dictate the crystal packing.
• The unique bonding of the benzoic acid molecule provides insights into supramolecular assembly in co-crystals.