Intermolecular H‐bond in propan‐2‐ol and its solutions with acetonitrile

Formation of propan‐2‐ol–acetonitrile dimers is manifested in the Raman spectra as an appearance of a band of aggregates in the high‐wavenumber side of the CN vibrational band of liquid acetonitrile (∼2 cm −1 ). The intensity of the band of aggregates changes with a change in the concentration of the mixture (1–0.05 mole fraction). For propan‐2‐ol we carried out nonempirical calculations of a structure of isolated dimer aggregates. The formation of an intramolecular H‐bond between the H and the O atom of the \newbox\osprulebox\newdimen\osprulewd\def\osprule#1#2{\global\setbox\osprulebox=\hbox{#1}\osprulewd=\wd\osprulebox\advance\osprulewd by ‐8pt\raise0.5pc\hbox{$\matrix{\hskip‐1pt\lower6.5pt\hbox{\vrule height #2pt}\lower4.5pt\hbox to \osprulewd{\hrulefill}\lower6.5pt\hbox{\vrule height #2pt}\cr\noalign{\vskip‐1pt}\hbox{#1}\cr}$}}$\osprule{{\rm HCO}}{2.5} \hbox{H}$ group of length 2.045 Å is possible in the monomer molecule. The CH 3 groups of alcohol are not equivalent. In the dimer formation, intramolecular H‐bond in the \newbox\osprulebox\newdimen\osprulewd\def\osprule#1#2{\global\setbox\osprulebox=\hbox{#1}\osprulewd=\wd\osprulebox\advance\osprulewd by ‐8pt\raise0.5pc\hbox{$\matrix{\hskip‐1pt\lower6.5pt\hbox{\vrule height #2pt}\lower4.5pt\hbox to \osprulewd{\hrulefill}\lower6.5pt\hbox{\vrule height #2pt}\cr\noalign{\vskip‐1pt}\hbox{#1}\cr}$}}$\osprule{{\rm HCO}}{2.5} \hbox{H}$ group is preserved. An intermolecular H‐bond of length 2.045 Å and energy 15 kJ/mole is formed between the H atom of one molecule and the O atom of another molecule of the OH. The length and energy of the H‐bond for the propan‐2‐ol–acetonitrile dimer formations calculate to 2.27 Å and 12.9 kJ/mole, respectively. The H‐bond is formed by σ‐electrons of nitrogen. The experimental data and the results of calculations are in good agreement. Copyright © 2007 John Wiley & Sons, Ltd.