Bond energy values

Bond energy values can be obtained from thermochemical calculations (p. 72) and a number are included in Table 2.70 together with the compound used in the calculation. 

In formulating a set of bond-energy values we first calculated the energies of formation of molecules from experimental values of the heats of combustion of the compounds6 and thermochemical data pertaining to the products of combustion—carbon dioxide, water, nitrogen, etc. The same values for the latter quantities were used as previously.4... 

The bond-energy values obtained in this way6 are given in Table I. It is noteworthy that the... 

Fig. 4.—Calculated one-electron bond energy-values (D/k, full curves) and squared bond strength values (S, dashed curves) for s-p hybridization.

Now we apply Equation, using average bond energy values from Table 6-2 - reaction — / j -S - bondsbroken - bonds formed A table helps us... 

Electronegativity does not have a unit. The most widely used electronegativity scale today was derived by Linus Pauling. He used bond energy values in the preparation of this scale. 

It is probable that electrostatic component of resulting interactions on anion-anion distances is registered in such a way. In fact, the calculated value 0.83E practically corresponds to the experimental bond energy values during phosphorylation (first line in table 4) and free energy for ATP in chloroplasts (second line in table 4). 

H. A. Skinner. A Revision of Some Bond-Energy Values and the Variation of Bond-Energy with Bond Length. Trans. Faraday Soc. 1945, 41, 645-662. 

Skinner, H. A. Revision of some bond energy values and the variation of... 

Similarly, we can calculate bond energies for any type of bond we wish to create. Refer to Appendix 1 for bond energy values. 

Table 3-3.—Bond-Energy Values for Alkali Hydride Molecules...

Bond-energy values for diatomic molecules ef alkali metals and for nlkali-raetal hydrides are given in Table 3-3. 

The bond-energy value given for each of the bonds F..F,... 

A fundamental assumption adopted in the formulation and use of the bond-energy values of Table 3-4 is that the energy of a molecule to... 

Fig. 4-3.—Square of bond strength (dashed curves) and calculated bond-energy values (full curves) for hybrid sp orbitals varying from pure p orbitals (a 0, left) to pure s orbitals (a = 10, right). The upper pair of curves are for L orbitals (2 and 2p), and the lower, with shifted vertical scale, for M orbitals (3s and 3p).

The bond-energy values are not designed for use with a molecule as unconventional as carbon monoxide, containing bivalent carbon. It seems probable, however, that the error involved in this application is not great. 

In Chapter 3 ana other chapters of this book much use is made of bond-energy values. These values are chosen in such a way that their sum over all of the bonds of a molecule which can be satisfactorily represented by a single valence-bond structure is equal to the enthalpy of formation of the molecule from its constituent atoms in their normal states. For example, the value of the O—H bond energy, 110 kcal /mole, is one-half the enthalpy of formation of U20(g) from 2H(g) and 0(g). 

There is at present no convenient, self-consistent source of all bond energies. The standard work is Cottrell. T. L. The Strengths of Chemical Bonds, 2nd ed. Butter-worths London, 1958, but it suffers from a lack of recent data. Darwent (National Bureau of Standards publication NSRDS-NBS 31, 1970) has summarized recent data on dissociation energies but did not include some earlier work or values known only for total energies of atomization rather than for stepwise dissociation. Three useful references of the latter type are Brewer, L. Brackett, E. Chem. Rev. 1961,61,425 Brewer, L. et al. Chem. Rev. 1963, 63, 111 Feber, R. C. Los Alamos Report LA-3164, 1965. The book by Darwent mentioned above also lists bond energy values for some common bonds. 

From AH° and any other required bond energies in Table 4-3, compute a second C-H bond-energy value for methane. 

Since the optimal ordinate Ea equals u/2, this permits one from the value of e to judge how far the given catalyst stands from its maximum specific activity. Since the optimal abscissa qoptimum catalyst for a given reaction. 

To obtain a comparative set of bond energy values, it is necessary to be consistent about the state of matter or type of experiment or calculation used. 

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