Oxygen dissociative energy

TABLE 19. Derived silicon-oxygen dissociation energies (kJmol ) ... 

Bond dissociation energies (BDEs) for the oxygen—oxygen and oxygen— hydrogen bonds are 167—184 kj/mol (40.0—44.0 kcal/mol) and 375 kj/mol (89.6 kcal/mol), respectively (10,45). Heats of formation, entropies, andheat capacities of hydroperoxides have been summarized (9). Hydroperoxides exist as hydrogen-bonded dimers in nonpolar solvents and readily form hydrogen-bonded associations with ethers, alcohols, amines, ketones, sulfoxides, and carboxyhc acids (46). Other physical properties of hydroperoxides have been reported (46). 

Physical Properties. Properties of some alkyl peroxyesters are Hsted in Table 13 and the properties of some alkyl areneperoxysulfonates are given in Table 14. Mass spectra (226), total energies, and dipole moments (227) oxygen—oxygen bond-dissociation energies (44,228) and boiling points, melting points, densities, and refractive indexes (44,168,213) have been reported for a variety of tert-huty peroxycarboxylates. 

The reaction rate of molecular oxygen with alkyl radicals to form peroxy radicals (eq. 5) is much higher than the reaction rate of peroxy radicals with a hydrogen atom of the substrate (eq. 6). The rate of the latter depends on the dissociation energies (Table 1) and the steric accessibiUty of the various carbon—hydrogen bonds it is an important factor in determining oxidative stabiUty. 

Figure 8.19 F.llingham diagram for the free energy of formation of metallic oxides. (After F. D. Richardson and J. H. F. Jeffes, J. Iron Steel Inst. 160, 261 (1948).) The oxygen dissociation pressure of a given M - MO system at a given temperature is obtained by joining on the lop left hand to the appropriate point on the M-MO frec-energy line, and extrapolating to the scale on the right hand ordinate for POi (atm).

FIGURE 2.16 The bond dissociation energies, in kilojoules per mole of nitrogen, oxygen, and fluorine molecules. Note how the bonds weaken in the change from a triple bond in N, to a single bond in F,... 

Water dissociation may take place either by electron impact, as the dissociation energy is relatively low (4.8 eV), or, to a greater extent by reactions with excited oxygen atoms (0( D)) [33,77,79] ... 

Possible pathways of the degradation reaction may be visualized for a linear hydrocarbon chain in which the reaction centre ( ) is formed by the effect of initiation (heat, light, oxygen, shear stress, etc.), see Scheme la. A complementary reaction site is denoted as (-). For example, when ( ) is a free radical site, (-) is also a free radical site, if ( ) is a cation, then (-) is an anion, etc. The three stages of the reaction depicted in Scheme la, are initiation, propagation and termination, respectively. The dissociation energies of bonds situated in a /(-position to the reaction site ( ) are considerably lower than those... 

Fig. 9 Deprotonation of cations radicals of synthetic analogs of NADH by oxygen or nitrogen bases in acetonitrile. Correlation between the intrinsic barrier and the homolytic bond dissociation energy of the cation radical (AH + —> A+ + H ).

---