For liquid ethylacetate the frequency maximums for parallel (I|| (v)) and perpendicular (I&highmod;(v)) polarized components of C=O vibrations band in Raman spectra are differed on 5.3 cm-1. At dilution ethylacetate in CCl4 and heptane or heating in this difference is decreased by displacement of I|| (v) maximum to the I&highmod;(v) maximum. In polar solvent, nitrometane, the picture is different - the frequency maxima difference is decreased though the displacement of I&highmod;(v) band maximum to the I|| (v)one. The results were explained by the complexity of C=O vibration bands, and existence within the band of two lines with the different depolarization ratio. The complexity of the band is the result existence in liquid ethylacetate the monomer molecules and molecular aggregations.
Quasiempirical calculations of stable molecular aggregations for dimethylsulfoxide were carried out by MINDO/3 method. The structure of the aggregates and energy of its formation for cases of two, three and four molecules were determined. It was shown that except monomer molecules are possible aggregations from two or three molecules. It was established that the aggregations form by charge interaction of polar molecules.
Apparently in liquid state of substance the tendency of aggregation formation remains. The presence of three imposed bands in Raman spectra of S=O vibrations for dimethylsulfoxide was connected, on our opinion, with this. The difference of depolarization ratio for imposed bands is connected with different distribution of charge on S=O bond for different aggregations.
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