Polarity and basicity of solvents. Part 1. A thermosolvatochromic comparison method
A thermosolvatochromic comparison method for measuring polarity and basicity parameters of solvents, which takes advantage of variations in solvent properties with temperature (0–105 °C), is proposed. The effects of the vibrational structure of the absorption bands on (i) the reference (homomorphism) line of non-hydrogen-bond donor and non-hydrogen-bond acceptor solvents and the temperature line of hydrogen-bond acceptor solvents, and thus on (ii) the precision and sensitivity of the method, are analysed for a range of indicators. 4-Nitroanisole and 4-nitrophenol are recommended as reference polarity and basicity indicators, respectively. The reference (homomorphism) line is to be taken from data for gas-state, perfluorinated hydrocarbons, alkanes, CCl4 and/or C2Cl4, 1,2-dichloroethane, and mono- and poly-halogenated benzenes.