Average bond dissociation energies, table

Use the average bond dissociation energies in Table 7.1 to calculate approximate reaction enthalpies (in kilojoules) for the following processes ... 

From Table 2.4, the average bond dissociation energy of a N=0 bond is 630 kJ mof, which is right in line with the Lewis structure of NO. The bond dissociation energy of each NO bond in NO2 is 469 k J mof, which is about half-way between a N-0 double and an N-0 single bond, suggesting that the resonance picture of NO2 is a reasonable one. 

Table 3.6 Average bond dissociation energies for a selecttion of single and multiple bonds...

The average bond dissociation energy for ferrocene is large (302 kJ mot 1. Table 15.9) as you might expect, but ii is even larger for vanadocene (369 kJ mol-1). Can you suggest any reasons that vanadocene is more reactive even though it is more stable ... 

Table 4.n Average bond dissociation energies of representative covalent hydrogen bonds at 298 K. From [i]. 

A standard bond dissociation energy is different from an average bond dissociation energy. The latter is just the value obtained by calculating the heat of atomization of a compound (the enthalpy change on converting the molecule to individual atoms) divided by the number of bonds from one atom to another in the molecule. For more details on this distinction, see reference 67. Blanksby, S. J. Ellison, G. B. Acc. Chem. Res., 2003, 36, 255. This reference provides the uncertainties for the values in Tables 1.10 and 1.11. 

TABLE 9.A.2 Average Bond Dissociation Energies (in kcal/mol Units) for Selected Bonds. ... 

Using the well-known alcoholysis reactions of titanium ethoxide in cyclohexane, the standard heat of formation of various titanium tetra-aUcoxides in liquid as well as gaseous states were determined and the average bond dissociation energy was calcu-lated ° as given in Table 2.8. 

If one looks at the average bond dissociation energies for X2, C-X, H-X, and C-H bonds (Table 2.2), an average heat of reaction for the halogenation of alkanes can be calculated. The results in kcal/mol are as follows F = -101, Cl = -22, Br = -4, and I = 16. The variation in these numbers comes from a continual decrease in H-X and C-X bond strengths in the series F, Cl, Br, and I. These heats of reaction reflect a dramatic change in reactivity. Free radical fluorination is so exothermic that it occurs spontaneously and very explosively. Chlorination and bromination can be controlled and are useful reactions. Free radical iodination rarely occurs. 

TABLE 1.9 Some Average Bond Dissociation Energies ... 

Table 3.34. The Ar—F bond lengths R, average Ar—F bond-dissociation energies (BDE), and vibrational frequencies of ArF species...

Fig. 6. Variation of the mean bond dissociation energy, D (MH-Cp) kJ mol-1, in MCp2 (M = Ti, V, Cr, Mn, Fe, Co, Ni) with average metal-cyclopentadienyl ring plane distance in well determined structrues (Ref.73)) r(M-Cp) pm. See Table 9...

TABLE 4.1. Average Homolytic Bond Dissociation Energies (kJ/mol) of R—X... 

Because similar bonds have similar bond dissociation energies, it s possible to construct a table of average values (Table 7.1) to compare different kinds of bonds. Keep in mind, though, that the actual value in a specific molecule might vary by 10% from the average. 

Values of average dissociation energies in text Table 2.4 are actually those for the property of bond enthalpy (see Chapter 6), measured at 298.15 K. The bond dissociation energies of diatomic molecules given in Table 2.3 apply at 0 K (absolute zero). 

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