Study of Intermolecular Associations in Liquid Acetonitrile From Ab-initio Calculations of Ir Frequencies and Intensities

Because of the great sensitivity of IR intensities of acetonitrile to the molecular environment, it should be possible to deduce information about the structure of liquid acetonitrile from measured IR spectra, provided the relationships between spectral characteristics and molecular environment are known. For this purpose, the IR spectra of linear, cyclic and antiparallel clusters are simulated: the results obtained match best the liquid phase spectrum for the cyclic trimer, and also for the antiparallel clusters, despite a residual discrepancy attributed to the inability of the model to mimic the liquid.