Hydrogen molecule explained

It is common knowledge that, in the case of the hydrogen molecule studied in a minimal basis set, the correlation error can be explained by the existence of ionic species in the hydrogen dissociation products ... 

The difference in reactivity ofC( D) from C( S) is explained by Donovan and Husain (310) on the basis of symmetry correlations between reactants (for example, carbon atom and hydrogen molecule) and products (methylidyne and atomic hydrogen). Figure IV—2 shows the correlation of C + H2 with CH + H. The reaction C + H2 is assumed to form CH2 of Cs symmetry (or C2. symmetry), which dissociates subsequently into CH + H. Correla-... 

This observation was explained in terms of the unusual electronic properties of pentaco-ordinated cations (Kollmar and Smith, 1970). The CHs species is best described as a hydrogen molecule with an abnormally long bond, 0-94 A, to which a deformed trivalent carbonium (carbenium) ion is coordinated. The energy of CHs was calculated to be 47 kcal mol-1 lower than that of H2 + CH3 (gas phase value) and two of the C—H bonds only of half the strength of a C—H bond in methane. This electronic structure, perhaps best being described as closely related to protonated hydrogen, is probably the reason for the reverse order of oxidation potentials observed. 

Complexes of the hydride ion with neutrals are invoked to explain some observed reactions, especially the loss of hydrogen molecules from alcoholates and enolates ... 

Figure 2 Schematic potential energy curve for the hydrogen molecules with scale at bottom of the curve exaggerated to show relation between n = 0 vibrational energy levels of the four isotopic forms of the molecules. Note that molecules containing a heavy isotope are more stable (have higher dissociation energies) than molecules with a light isotope. Isotope fractionations between molecules are explained by differences in their zero-point energies...

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