Phase studies and thermochemistry of the aluminium bromide–pyridine system

Abstract

Phase studies have shown that the compounds C₅H₅N,AlBr₃ and 2C₅H₅N,AlBr₃ melt congruently at 116·0 and 183·4–185·1°, respectively, and 3C₅H₅N,AlBr₃ melts incongruently at 170°. The heats of formation (–ΔH₁; kcal. mole^–1) of the crystalline complexes from crystalline aluminium bromide and liquid pyridine at 25°, determined calorimetrically, are 32·6, 45·7, and 56·3, respectively. The heat of sublimation of the 1 : 1 adduct is 19·9, the gas-phase heat of formation 45·3, and the dissociation energy, D(C₅H₅N–AlBr₃), 73·6 kcal. mole^–1.