THE BICHLORIDE ION¹

Calorimetric studies in the halide-hydrogen chloride systems

“…are given in the first column of Table IV. The enthalpy changes for reaction 2 are closely related to the hydrogen bond energies defined for x-(g) + HCl(g) = HClX-(g) (3) Although these latter values cannot be calculated as the solvation enthalpies for the nonspherical HC1Xgaseous ions are not known, it is expected, on account of ion sizes4 alone, that the solvation enthalpies of HC1Xare smaller than that of X-, so that the AH values for reactions 2 represent minimum values for the hydrogen bond energies corresponding to reactions 3. Some estimates of solvation enthalpies of halide and perchlorate ions,4 respectively (Cl-, 80.1; Br-77.0; I-, 72.1; C104-, 62 kcal mol-1), indicate that the hydrogen bond energies may be substantially higher than the very minimum values quoted in Table IV.…”

A Highly Conductive Room Temperature Molten Fluoride: EMIF⋅2.3HF

“…45 Density.- Figure 6 shows the temperature dependence of the density of EMIF•2.3HF. The density at 298 K is 1.135 g cm Ϫ3 , lower than that found for the other RTMS containing fluoroanions.…”

Thermodynamic Calculations for Reactions Involving Hydrogen Halide Polymers, Ions and Lewis Acid Adducts. 1. Polyfluorohydrogenate(1-) Anions (HnFn+1-), Polyfluorohydrogen(I) Cations (Hn+1Fn+), and Hydrogen Fluoride Polymers (HF)n

“…Proton affinities for HF and HCI (reactions 7 and 8) are known,4ab14 as are the corresponding halide affinities (reactions 5 and 6).2e 3a15 Payzant and Cunningham determined AH for reaction 14,7 ********16 and dissociation energies for the dimers (reactions 9 and 10) have been estimated.7ce For reaction 6, the equilibrium constant has been reported to be 500 in nitrobenzene at 298 K (AG°= -15 kJ/mol),17 «600 at 304 K in s-tetrachloroethane (AG°= -16 kJ/mol),18 and 67 ± 18 in AlCl3:ImCl at 363 K (AG°= -13 kJ/mol). 19 In his review of dihalohydrogenate(l-) ions, Tuck quotes AG°values ranging from -4 to kJ/mol for reaction 5.2f Our own NMR and pressure-composition isotherm studies estimate AT to be 715 ±76 (AG°= -16.2 kJ/mol), 3.28 ± 0.05 (AG°= -2.93 kJ/mol), 0.72 ± 0.02 (AG°= +0.81 kJ/mol), and 220 ± 20 (AG°= -13.3 kJ/mol, AH0 = -22.8 kJ/mol and A5°= -31.8 J/K/mol) for reactions 6, 17, 18, and 19 respectively in HChlmCl melts.Id HCI + HC12~-H2C13' (17) HCI + H2C13~-H3C14~ (18) cr + h2ci3"-*2hci2- (19) If theoretical calculations are to be truly helpful in predicting the outcomes of reactions at equilibrium, they should provide AG°, AH°and AS°. The difference between AH at 298 K and AU at 0 K, even with zero point energy differences taken into account, involves thermal energy (usually small) as well as the term AnRT, where An is the change in the total number of moles of gas during the reaction.…”