Bond dissociation energy values hydrogen-oxygen

Homolytic bond dissociation energies (BDEs) for the detachment of a hydrogen atom (radical), are shown in Table 18. This type of comparison is expected to be less accurate than PAs, because different numbers of pairs of electrons are involved on the two sides of equation 266. For example, the gas-phase BDE of H20 is calculated from Table 17 at 114 kcal mol"1, where the experimental value, corrected for zero-point vibrational energy which was not taken into account in the theoretical calculation, is 126 kcal mol"15. Thus, as expected, the calculation underestimates BDEs because of the relatively poorer description of the B—H system relative to B- + H A larger basis set and higher level of theory are required to achieve better accuracy for BDEs68. Nonetheless, we can examine the BDE values as a function of substituent X, and compare sulphur-bonded to oxygen-bonded H atom dissociation. 

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