Hydrogen fluoride thermodynamic data

In a recent thermodynamic and spectroscopic study Redington66 -68) evaluated AH and AS for the formation of cyclic and open-chain oligomers of hydrogen fluoride. His best fit to vapor density, heat capacity, excess entropy, excess enthalpy, and infra red absorption data shows a monotonous increase in AH per hydrogen bond with increasing number of HF molecules both for open-chain and cyclic clusters, using the relation... 

Hydrogen fluoride presents another example of a fluid in which hydrogen bonding is crucial for the structural and thermodynamic properties. Figure 1.20 draws the HF vapor-liquid coexistence curve obtained from the RISM/KH theory in comparison with that following from the molecular OZ/RHNC approach [109] and the simulation data... 

A topic related to that of the gas-phase acidities of phenols is the quest for quantitative data on the thermodynamic stability of hydrogen-bonded complexes, or clusters , [ArO-H X ] and [ArO H-X] between phenols and various anions derived from other Brpnsted acids. The thermodynamics of cluster formation of the phenolate ion [1 — H] with water, ethanol and acetic acid have been determined by using a pulsed electron-beam mass spectrometer and their stability was found to increase with the gas-phase acidity of the Br0nsted acid. For example, association of [1 — H] with H2O is much weaker. A// = —15.4 kcalmor , than that of [1 — H] with CH3COOH, AHq = —27.4 kcalmor The association enthalpy of the complex of phenol and fluoride ion, [1 F ], has been measured to be A//° = —41.3 kcalmor , much stronger than... 

It is reasonable to postulate that the main driving force for the reaction of (MeC5H4)3U(t-Bu) with hexafluorobenzene is thermodynamic. A weak uranium-carbon bond and a carbon-fluorine bond have to be broken. This is offset by the formation of a strong uranium-fluorine bond and either a carbon-carbon or a carbon-hydrogen bond. As illustrated in equation 8, the uranium-fluorine bond energy can be estimated to be on the order of 150 kcal/mol based on known thermochemical data for uranium fluorides (21), The carbon-fluorine bond dissociation energy for hexafluorobenzene is reported to be 154 kcal/mol (17), The... 

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