1-Hexadecyl-3-methylimidazolium chloride: Structure, thermal stability and decomposition mechanism

Abstract The structural parameters of 1-hexadecyl-3-methylimidazolium chloride (C 16 MImCl) were computed using B3LYP level of density functional theory. Presence of water of hydration was theoretically studied and rationalized using TG and FTIR heating experiments. Conformation analysis using Raman spectroscopy suggested that C 16 MImCl exist as a trans conformer. XRD analysis revealed that C 16 MImCl is a crystalline solid with crystallite size of 37.8 nm. Crystalline phase transition to smectic phase was observed in DSC analysis with enthalpy of 21.2 kJ/mol. The binding energy of 371.1 kJ/mol indicate a higher stability for C 16 MImCl, supported by thermal analysis (T s  = 296 °C) and frontier orbital gap value (4.09 eV). Thermal decomposition products of C 16 MImCl were identified using pyrolysis GC-MS and the decomposition mechanism was established. Bimolecular nucleophilic substitution reactions ( E a  = 122 ‐ 131 kJ/mol) were identified as the preferred pathway over the elimination route ( E a  = 167.7 kJ/mol). Use of C 16 MImCl as a template for copolymerization of aniline and pyrrole was also demonstrated.