E. S. Sashina

Products of thermodegradation of 1-alkyl-3-methylpyridinium halides are investigated by the method of gas chromatomass spectrometry. The main products of the reaction are 3-methylpyridine and the corresponding alkyl halide. It was supposed that thermodecomposition of pyridinium ionic liquids proceeds similar to that of imidazolium ionic liquids by dealkylation with elimination of the substituent at the nitrogen atom of the pyridinium ring via S_N2 mechanism. The presence of 5 wt % of cellulose decreases the onset temperature of thermodecomposition by 15–20°С.

1-Alkyl-3-methylpyridinium-based ionic liquids with substituents from C₂ to C₁₀ and anions Cl⁻ and Br⁻ were synthesized, and their dissolving power toward the cellulose was investigated. The results of quantum-chemical calculations of molecules of ionic liquids are presented.

The results of the calorimetric studies of the enthalpies of mixing of some ionic liquids, 1-butyl-3-methylimidazolium chloride and acetate, with water, pentanol, dimethyl sulfoxide and dimethylformamide are presented. Protic solvents interact with the ionic liquid anion, wheras aprotic, with the cation. The mixing enthalpy depends on the dissociation degree of the ionic liquid.

The enthalpies of dissolution of fibroin in imidazole-based ionic liquids were determined, and the contribution of polymer crystal structure decomposition to the enthalpy of dissolution was estimated. The heat of mixing of imidazole ionic liquid with water was described.

Main geometric parameters and electronic structure of molecules of alkylpyridinium chlorides, bromides, and acetates were calculated by a quantum-chemical method. The influence of the electronic structure of molecules on their dissolving power with respect to cellulose was analyzed.

Experimental and calculated data on the effect of anion and cation structure on the dissolving power of ionic liquids based on imidazole toward the natural polymers cellulose, fibroin and keratin are presented.

The literature data and our quantum-chemical electron density distribution calculations were compared with experiment for the N-methylmorpholine-N-oxide molecule