Hydrogen bonding of linear and cyclic amides in ionic liquids

The present work focuses on hydrogen bonding of linear and cyclic amides (formamide, N-methylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, 2-pyrrolidone) in several ionic liquid (1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [BMIM][NTf2], 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4], 1-butyl-3-methylimidazolium trifluoromethanesulfonate [BMIM][TfO], 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF6], triethylsulfonium bis(trifluoromethylsulfonyl)imide [Et3S][NTf2], Trimethylpropylammonium bis(trifluoromethylsulfonyl)imide [TMPAm][NTf2]). The solution enthalpies of amides in ionic liquids were measured by solution calorimetry at infinite dilution. The hydrogen bond enthalpies were calculated based on solution enthalpies of amides in ionic liquids. The hydrogen bond enthalpies of linear and cyclic amides in ionic liquids and organic proton acceptors were compared. The influence of active proton donor center on the formation of hydrogen bond complexes between amides and ionic liquids was analyzed.