Hydrogen bonding: Part 29. Thermodynamics of dissociation and stoichiometric study of the lower hydrates of tetraethylammonium and tetrapropylammonium chlorides

Abstract

Thermodynamic parameters for the dissociation of three tetraalkylammonium chloride hydrates have been determined by equilibrium vapor-pressure measurements. Hydrogen-bond energies are at least 8 kcal mol −1 per OH⋯Cl bond in tetraethylammonium chloride monohydrate. Hydrogen-bond energies average at least 6 kcal mol −1 in tetraethylammonium chloride tetrahydrate; however, as each H 2O forms one OH⋯Cl and one OH⋯O hydrogen bond, some bonds will be stronger and some weaker than 6 kcal mol −1. Hydration water in tetrapropylammonium chloride monohydrate is less tightly bound than in tetraethylammonium chloride monohydrate. These three hydrates are the only hydrates formed by the chloride salts of the two cations; the previously reported tetrapropylammonium chloride·2.5 H 2O is a dispersion of H 2O in solid monohydrate. Infrared spectra show that both monohydrates contain the same planar (Cl −·H 2O) 2 cluster of C 2h symmetry.