Valence-shell molecular orbitals of linear HXXH

the more highly destabilized is its antibonding counterpart. The symmetric member of any pair of symmetry-adapted combinations is placed below its antisymmetric partner, which is bisected by a nodal plane. As usual, the MOs are labelled according to their irreps in both D2/1 and Doo/i- 

The most important effect of bending the XH bonds away from linearity is to convert one tt orbital and its antibonding partner into combinations of lone-pair hybrid orbitals, the former going up in energy and the latter going down. In addition, the consequent desymmetrization allows each of these two 

One 7T -orbital goes down strongly in each bending mode, as expected, but its bonding partner goes up very little - if at all. 

The excited states of both spin states are bent, as expected, but take up different conformations the singlet is indeed trans but the triplet is cis. 

Despite their obvious quantitative deficiencies, the ideas developed in this section are instructive, and the methods based on them are useful - in their proper qualitative context  

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Figure 4.5. Valence-shell molecular orbitals of linear HXXH...

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