Energetics of reaction

Hartree-Fock theory is very useful for providing initial, first-level predictions for many systems. It is also reasonably good at computing the structures and vibrational frequencies of stable molecules and some transition states. As such, it is a good base-level theory. However, its neglect of electron correlation makes it unsuitable for some purposes. For example, it is insufficient for accurate modeling of the energetics of reactions and bond dissociation. 

It is to be hoped that measurements will be made in the near future which will put more substantial flesh on the skeleton of known bond enthalpy contributions in organo-transition metal compounds, so that a better understanding of the energetics of reactions such as olefin disproportionation (metathesis) and hydroformylation may be achieved. 

It is important to stress that the energetics of reactions 4.25 and 4.27 are usually not amenable to direct experimental investigation. Indeed, proton affinities, gas-phase basicities, and gas-phase acidities reported in the literature were not... 

The enthalpy of reaction 38 is ca 13 kJ mol" for the case of cyclohexanone wherein R R = —(CH2)5—. This difference is compatible with intermolecular hydrogen bonding as would be found for the benzoquinone oxime tautomer. In order to understand the energetics of reaction 39, we derived the solid phase enthalpy of formation of nitrosobenzene... 

Density functional and MP2 models are needed to accurately account for the energetics of reactions where bonds are broken or formed and to describe absolute activation energies. Hartree-Fock models are unsatisfactory, but properly account for relative activation energies expressed in terms of isodesmic processes. MP2 models are also satisfactory here but density functional models sometimes lead to problems. 

The infancy of these first-principles methods as applied to periodic zeolite lattices means that further detailed work is necessary, particularly in the area of verification of the ability of the pseudopotential to reproduce dynamic as well as static structural properties. However, the results found with these methods demonstrate that the debate concerning the modeling of the activation of methanol within a zeolite is far from concluded. The proton transfer to methanol as a reaction in its own right is, however, of relatively little interest. It does not govern the pathway or energetics of reactions such as dehydration to give dimethyl ether (DME). These are governed instead by the individual transition states that lead to the products, as we discuss in the next section. 

A stated objective of many of the reported studies of the catalytic properties of alloys has been to elucidate the significance of the band structure of the metallic phase (i.e., the energy levels of the d electrons) in determining the energetics of reaction (i.e., the value of E). While significant correlations of the values of E with band structures have been found in several instances [e.g., (25,255)], the interpretation of results is not always straightforward (237) and it may be necessary to incorporate due allowance for other factors that may exert some control over the mechanisms of reactions. Such factors include the possible presence of more than one alloy phase (207), dissolution of hydrogen in the alloy (207), and the composition and disposition of elements in the active outer surface of the alloy under reaction conditions (28,113,208). 

This suggests very little additional destabilization arising from an array of /1-diketones. Equivalently, there is insignificant enthalpic consequence of e- or greater separation on the energetics of ketones, a finding consonant with the energetics of reaction 54. 

Henglein A (1980) Energetics of reactions of Oaq and of 0--transfer reactions between radicals. Radiat Phys Chem 15 151-158... 

The increase of the sticking probability at higher kinetic energies was attributed to a direct access of the chemisorbed molecular states [81, 83, 86, 87], which is also sketched in Fig. 9. Now, such an one-dimensional sketch of the potential energy surface along some suitable reaction coordinate is certainly very helpful for a compact presentation of the energetics of reaction intermediates and products. Furthermore, it can be used as a basis for a kinetic modelling of a reaction. However, in... 

Ionization energy and electron affinity both refer to the energetics of reaction of atoms and ions in the gas phase. 

As in the bulk oxide, the redox behavior of ceria surfaces was examined on the basis of the energetics of reaction 8.2, which involves reduction of cerium species to... 

In Methanosarcina, acetate is activated by acetate kinase (Reaction 34) and phosphotransacetylase (Reaction 35) before cleavage. These enzymes are produced by Methanosarcina grown on acetate [236-240]. The energetics of Reaction (8) (Table 2) suggest that at most 0.5 mol ATP can be generated from 1 mol of acetate [184]. Since... 

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