COMPOSITION AND STRUCTURE OF HETEROASSOCIATES FORMED IN a BINARY LIQUID SYSTEM HF-CH3CN
E. G. Tarakanova, G. V. Yukhnevich
Keywords: binary liquid system, IR spectrum, quantum chemical calculation, hydrogen bond, heteroassociates, fluoric hydrogen, acetonitrile
Pages: 707-716
Abstract
The concentration dependence of normalized absorbance (to the total number of moles of components in one liter) of HF solutions in acetonitrile (1:12-10:1) is analyzed. It is found that in the binary liquid system (BLS) under study molecular complexes with stoichiometric 1:1 and ~10:1 ratios of molecules occur along with the heteroassociates (HAs) found previously with the ratio HF:CH3CN of 4:1. For each of the HAs the concentration range at which it is formed in BLS is evaluated, and the positions of HF stretching vibrational bands are found. Optimum configurations and vibrational frequencies of molecular complexes (HF)m⋅(CH3CN)n (m = 1-6, n = 1-2) of various topology are calculated using the density functional method (B3LYP/6-31 ++ G (d, p)). Their relative stability and the structure peculiarities are studied; complexation tendencies in the HF-CH3CN system are revealed. The structure of HAs with 1:1 and 4:1 stoichiometric ratios of molecules is determined by comparing the results of calculations and experiment.
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