Energetics of formation

Benoit, F.M. Harrison, A.G. Lossing, F.P. Hydrogen Migrations in Mass Spectrometry. III. Energetics of Formation of... 

Rollgen, F.W. Heinen, H.J. Energetics of Formation of Doubly Charged Benzene Ions by Field Ionization. Z. Naturforsch. 1975, JOA, 918-920. 

Equations (4.7) and (4.8) are both very useful when analysing surfactant aggregation behaviour and experimental cmc values. The difference in standard chemical potentials - Pi must contain within it the molecular forces and energetics of formation of micelles, which could be estimated from theory. These will be a function of the surfactant molecule and will determine the value of its cmc. 

It is instructive to consider the energetics of formation of larger molecules such as H4. The hypothetical H4 molecule could have three possible symmetric structures tetrahedral, square planar or linear. The results of MO calculations on these molecules are shown in Table 7.1. The nearest H-H distance is assumed to be 100 pm, chosen because it minimized the total energy of the linear form of H4. 

In principle, we can use the Born-Haber cycle to predict whether a particular ionic compound should be thermodynamically stable, on the basis of calculated values of U, and so proceed to explain all of the chemistry of ionic solids. The relevant quantity is actually the free energy of formation, AGf, and this is calculable if an entropy cycle is set up to complement the Born-Haber enthalpy cycle. However, in practice AHf dominates the energetics of formation of ionic compounds. 

Barrer, R. M., Edge, A. J. V. (1967) Gas hydrate containing argon, krypton, and xenon Kinetics and energetic of formation and equilibrium. Proc. Roy. Soc., London, A300, 1-24. 

This has been attributed to the participation of the nitrogen atom in the reaction owing to more favorable energetics of formation of a six-membered rather than a four-membered ring117. Hydrolysis of 113 gives 114. 

Among the fluorides, lanthanum forms only LaFs, whilst cerium forms CeFs and CeF4. (Tetrafluorides are also known for Pr and Tb, see Section 3.4). Why do neighbouring metals behave so differently First, examine the energetics of formation of LaFs using a Bom-Haber cycle. 

Second, isomorphus substitution of aluminum for silicon in the tetrahedral layer, or iron, magnesium, titanium, lithium, and so forth, for aluminum in the octahedral layer, will affect the energetics of formation of the mineral. Such substitutions may vary from trace impurity to complete replacement. 

The energetics of formation of the H20 --H20--HC1 complex are reported in Table 5.31, in a format comparable to that for H20"-HF"HF in Table 5.29. All data were obtained at the MP2 level and are corrected for BSSE by the counterpoise procedure. The three basis sets all contain polarization functions and yield comparable results. The binding of HCl to the pre-formed water dimer (step lb) is considerably more favorable than its binding to a water monomer, as in step 2a. This enhancement is referred to as E p in Table 5.31, and amounts to between 2 and 3 kcal/mol. (The same quantity is identically equal to the enhancement of binding of water to HjO—HCl as compared to HCl.) It is worth noting that whereas the total binding energy in the appropriate row of Table 5.31 is rather insensitive... 

A mild correlation of the polarizabilities exists with the softness that can be ascribed to the ions. The softness is related to the difference between the energetics of formation of the ion from the neutral species on the one hand (loss or gain of electrons) and its enthalpy of hydration (Sect. 2.3.1) on the other. In the hydration process the charge on the ion itself is neutralized to some extent by the gain or loss of pairs of electrons by coordination with the solvent. The softness parameter was given normalized numerical values by Marcus (1986), for cations according to ... 

Fuger (1979) and Fuger et al. (1983) reviewed experimental thermodynamic data on complex halides of the f elements, almost all of which were limited to ternary An chlorides. Jenkins and Pratt (1979) used an ionic model for lattice-energy calculation to place the energetics of formation of complex halides of d and f transition elements (from binary halides)... 

Lipkowski, in his analysis of the energetics of formation of Werner clathrates, adds an enthalpic term for the dilation of the yd-lattice when it accommodates the guest. This term is dependent on the size of the guest as well as the... 

Activation Parameters.— Negative heats of activation have previously been reported for some outer-sphere reactions, - and it has been suggested that some special factor, not covered by the simple Marcus theory, might need to be invoked to explain them. (It will be recalled that negative heats of activation of some inner-sphere reactions have been rationalized in terms of the energetics of formation of precursor complexes.) Marcus and Sutin point out, however, that negative AH values are theoretically predicted, under certain conditions. On differentiating equation (1) with respect to temperature, they obtain... 

Table 4.1. gives some typical bond dissociation energies obtained as a result of making many observations on the energetics of formation and dissociation of many molecules. 

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