HYDROGEN-BONDING .46. THERMODYNAMIC AND IR STUDY OF STABILITY AND STRUCTURE OF TETRAETHYLAMMONIUM FLUORIDE CENTER-DOT-2 75H2O, TETRAETHYLAMMONIUM FLUORIDE-CENTER-DOT-2 00H2O, TETRAMETHYLAMMONIUM FLUORIDE-CENTER-DOT-300H2O, AND TETRAETHYLAMMONIUM FLUORIDE-CENTER-DOT-500H2O

An equilibrium vapor pressure study of the dissociation of tetraethyla mmonium fluoride.2.75H2O to the dihydrate demonstrates that hydrogen b onds between H2O and F-, and between H2O and H2O are broken in this pr ocess. This conclusion is based on comparison of the observed enthalpy of dissociation with values calculated for various patterns of hydrog en bond breaking. For these calculations a value of approximately 14 k cal mol-1 for HOH ... F- hydrogen bonds in the hydrates was estimated by comparison of crystalline state and gas phase water-halide hydrogen bond strengths. Coupled with the IR spectrum, this information leads to a proposed formulation for the water-fluoride ion structure of the dihydrate in which C2h planar (H2O.F-)2 clusters are linked by H2O mol ecules which bridge between H2O in one cluster and F- in an adjacent c luster. Material with the composition of tetramethylammonium trihydrat e is an extraordinarily hard, crystalline substance; dissociation vapo r pressure measurements suggest that only HOH ... OH2 hydrogen bonds a re broken as this material dehydrates to the dihydrate. Stoichiometric liquid tetraethylammonium pentahydrate can be nucleated to a crystall ine solid for which diffraction studies should be possible.