A NMR study on the interactions of 1-alkyl-3-methylimidazolium ionic liquids with acetone

H-1 and C-13 NMR chemical shifts have been determined to investigate the interactions of acetone with room temperature ionic liquids ([C(4)mim][PF6], [C(6)mim][PF6], [C(8)mim][PF6] and [C(6)mim][BF4]) at various acetone mole fractions. Changes in the chemical shifts of hydrogen and carbon atoms of the above systems indicated that hydrogen bonds were formed between the ring protons, the methyl and methylene next to the nitrogen of the ionic liquids and the carbonyl oxygen of the acetone molecules. The strength of hydrogen bond was found to be influenced not only by the type of the anion but also by the length of alkyl chain on the imidazolium ring of cations. At the same time, ab initio calculations have been performed to support the NMR results.