H dissociation energy

The C-H bond-dissociation energies Z>c-h of the acetals 130 and 131, monothioacetal 132, and the dithioacetal 133 (Figure 7) were calculated from experimental reaction kinetic data <2005MI379>. The C-H dissociation energies of the 1,3-dithiane derivative 133 proved to be lowest, followed by the 1,3-oxathiane derivatives 132,... 

Figure 7 Calculated C-H dissociation energies of 2-substituted-1,3-heterocycies.

Our original theoretical interest in N, F compounds was stimulated by the observation of an apparently anomalous pattern in bond dissociation energies of some of these compounds. In 1961 at an American Chemical Society Symposium on Chemical Bonding in Inorganic Systems, C. B. Colburn of Rohm and Haas at Huntsville mentioned that while the N—H dissociation energies in NH3 were D(H2N—H) > D(HN—H) > D(N—H), in NF3 the order was D(F2N—F) < D(FN—F). At that time we postulated that the reason must largely be caused by the fact that... 

Table 1 M-H dissociation energies of some M-H cations, neutrals, and anions in the gas phase and of some hydride complexes in solution...

The M H dissociation energies see Bond Dissociation Energy) estimated from ion beam experiments are quite... 

Thus, we should conclude, that alkanes are extremely inert toward normal (i.e., not very reactive) reagents in reactions that proceed more or less selectively. In many respects, alkanes, especially lower ones (methane, ethane) are similar to molecular hydrogen. Indeed, like alkanes, dihydrogen while being inert towards dioxygen at ambient temperatures can be burned in air to produce thermodynamically stable water. The values of the C-H and H-H dissociation energy... 

Hildenbrand, D. L., Lau, K. H., Dissociation energy of the molecule AlBr from equilibrium measurements, J. Chem. Phys., 91, (1989), 4909-4911. Cited on page 248. 

Optimizing the structure of this system at the Cl level results in the linear structure with a ScN-H dissociation energy of 118.5 kcal/mol (Kunze, K.L. and Harrison, J.F., MSU, unpublished results). This is a remarkably strong NH bond (free NH has a of 80... 

In many cases, however, it is possible to choose less demanding reference systems than the isolated atoms. Consider for example calculating the C—H dissociation energy of CH4. In a direct calculation this is given as the difference in total energy of CFLt and CH3 + H. 

Wodrich, M. D. Schleyer, P. v. R. Org. Lett. 2006, 8, 2135 and supporting information. Moreover, Stanger was able to correlate C -H dissociation energies of alkanes on the basis of the calculated hybridization of the orbital used for C-H bonding, which was in turn a function of molecular geometry. Stanger, A. Eur. j. Org. Chem. 2007, 5717. 

The stability of a radical depends on the rate of its disappearance or formation according to the reaction conditions. The thermodynamic stability of a radical is related to the ease of dissociation of the R-H bond to give R and H or the R-H dissociation energy. The thermodynamic stability of a radical depends on double bond conjugation and electron delocalization stabilized by resonance in allylic systems produced by hydrogen abstraction in polyunsaturated lipids (see Chapter 2). 

Long, L. H., Dissociation Energies of Metal-Carbon Bonds and the Excitation Energies of Metal Atoms in Combination, Pure Appl. Chem. 2 [1961] 61/9. 

The NjH and N H radicals are thereby stabilized relative to H N—NH and HN = N as dissociation products, with the odd electron located in only one nitrogen atomic orbital. Consequently, the N-H dissociation energies for... 

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