The Hydrogen-Bonding Interactions between 1-Ethyl-3-Methylimidazolium Lactate Ionic Liquid and Methanol

1-Ethyl-3-Methylimidazolium lactate ([EMIM][LAC]) is an environmental friendly ionic liquid with potential industrial applications. Attenuated total reflectance infrared spectroscopy (ATR-IR) and density functional theory (DFT) calculations were employed to investigate the molecular interactions between methanol and [EMIM][LAC]. The infrared spectra were analyzed by two methods: excess spectroscopy and two-dimensional (2D) correlation spectroscopy. In the ATR-FTIR spectra, v(C4,5-H), v(C2-H), v(alkyl), v(-OD), and v(-COO) all show blue shifts upon addition of methanol. 2D correlation analysis indicated that the v(imidazolium ring C-H) band varies before that of v(alkyl C-H) with increasing CD3OD content. The following sequential order of interaction strength is established by DFT calculations: EMIM-methanol -LAC > EMIM-LAC > LAC-methanol > EMIM-methanol.