Polarity, hydrogen bonding, and structure of mixtures of water and cyanomethane

The polarity of mixtures of water and cyanomethane was established from measurements of Kamlet and Taft's (KT's) π*, their hydrogen bond acceptance ability from measurements of KT's β, and their hydrogen bond donation ability from measurements of KT's α, with suitable solvatochromic indicators. The structure of these mixtures was explored by use of thermodynamic data from the literature and the application of the quasi-lattice quasi-chemical (QLQC) and the inverse Kirkwood-Buff integral (IKBI) methods. It is concluded that these methods point toward strong so-called microheterogeneity in these mixtures, i.e., preference for neighbors of the same kind, that extends over several concentric shells around a given molecule. This preference decreases with increasing temperatures. The polarity and hydrogen bonding ability results are explained in terms of these structural features of the mixtures.