Thermodynamic properties of hydrogen-bonded dimers B⋯HF from spectroscopy: B = HCN, CH3CN, HC2CN, (CH3)3CCN and H2O

Abstract

The rotational and vibrational spectra of several hydrogen-bonded dimers B⋯HF have now been investigated in sufficient detail to allow the thermodynamic properties of B⋯HF to be evaluated with useful accuracy. Dissociation energies D₀ for dimers B⋯HF are known from the measurement of absolute intensities of rotational transitions in equilibrium gas mixtures of B, H and B⋯HF. Together with vibrational separations and rotational constants, the D₀ have been used to estimate ΔH_m(T) for the reaction B + HF = B⋯HF where B = HCN, CH₃CN, HC₂CN, (CH₃)₃CCN and H₂O. The standard spectroscopic entropies S(T, M) have been evaluated for each participant M in the reaction and thence ΔS_m(T), ΔG_m(T) and K_m(T). Finally, standard functions for each B⋯HF at 298.15 K are tabulated.