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

• For the first time, excess spectroscopy was used to analyze near-infrared spectra.
• Dimer, trimer, and multimers of C2H5OH were identified in its mixtures with CH3CN.
• Moving-window 2DCOS show concentration-dependent changes of H-bonding complexes.

The hydrogen bond interactions in C2H5OHCH3CN 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 C2H5OH, and C2H5OH⋯CD3CN hydrogen bonding complex, have been identified in the binary system C2H5OHCH3CN 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 C2H5OH are weakened and C2H5OH multimers dissociate. Meanwhile, C2H5OH dimers and C2H5OH⋯CD3CN hydrogen bonding complex form, and the former also transform to the latter. The dissociation of C2H5OH multimers slows down gradually during the dilution process and at the mole fraction 0.7 of acetonitrile, all the C2H5OH multimers have dissociated.