Hydrogen bonding interactions in ethanol and acetonitrile binary system: A near and mid-infrared spectroscopic study

Abstract The hydrogen bond interactions in C 2 H 5 OH CH 3 CN binary system have been studied in detail by near-infrared spectroscopy (NIR), attenuated total reflection (ATR) mid-infrared spectroscopy (mid-IR), and density functional theory (DFT) calculations. The collected spectra were analyzed with excess spectroscopy and two-dimensional correlation spectroscopy (2D-COS) including moving-window 2D-COS. The main conclusions are: (1) A number of species, namely multimer, trimmer, and dimer of C 2 H 5 OH, and C 2 H 5 OH⋯CD 3 CN hydrogen bonding complex, have been identified in the binary system C 2 H 5 OH CH 3 CN experimentally. The linear relationship between the observed and calculated wavenumbers of the concerned species assisted us in doing the assignments. (2) Adding acetonitrile, the hydrogen bonds in C 2 H 5 OH are weakened and C 2 H 5 OH multimers dissociate. Meanwhile, C 2 H 5 OH dimers and C 2 H 5 OH⋯CD 3 CN hydrogen bonding complex form, and the former also transform to the latter. The dissociation of C 2 H 5 OH multimers slows down gradually during the dilution process and at the mole fraction 0.7 of acetonitrile, all the C 2 H 5 OH multimers have dissociated.