Numerical Values of Bond Dissociation Energies

Numerical values for a number of bond dissociation energies are given in this chapter. It is intended to be complete as far as directly determined dissociation energies are concerned some dissociation energies deduced thermochemically from heats of formation of radicals or atoms are included, often for purposes of comparison with directly determined values, but the list is not intended to be exhaustive or critical in this respect, and the reader can supply the missing values by simple arithmetic. Often older or less reliable estimates of dissociation energies are not discussed. 

Gaydon 166 gives Z)(B - H) in the diatomic molecule as 3 0 0-4 eV, Herzberg2i7 an upper limit of 3 51 eV. Nothing appears to be known about D B H) in polyatomic molecules. 

There is no very reliable value for D(GH -H) in methylene. The electron impact experiments of McDowell and Warren i give 3 4 0 3 eV (78 kcal). Their work leads to a value of 120 - 140 kcal see Section 8.2.2.6). Another consideration of the electron impact data 63 leads to 88 kcal for D(CH H), whence Lc i39 kcal. Possibly the best method of obtaining Z)(GH -H) is to decide upon D(G- H), D(GH2 H), and D(GH3-H). These data, together with D H and A/i/(GH4), can be used to deduce D(GH -H). If we accept D CH) and (GHa H) to be 80 and 101 kcal respectively, and take Zq = 138 kcal (Section 8.2.2.6), we deduce D(GH2 H)+D(CH H) = 179 kcal. Evidence on Z)(GH2 -H) suggests Z)(GH -H) - 92 kcal, but this is by no means certain. 

An upper limit for JD(GH2 H) has been deduced by Laidler and Casey 287 on the basis of the work by Bawn and Dunning 26 on the 

Here NaCl is vibrationally excited and Na electronically excited. The sodium excitation requires 48-3 kcal, so that reactions 1 and 2, with formation of normal NaCl, must jointly be exothermic by this amount, so that for 

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