Carbonyl group interaction diagram

Fig. 16 Energy diagram for the hydrogen abstraction reaction of ketones showing the interaction of the ground state and n,rc excited state curves, (a) In-plane approach. A real crossing occurs when the carbonyl group and the C—H bond lie in a plane since the two state curves are of opposite symmetry, (b) Out-of-plane approach. An avoided crossing (dotted lines) occurs when the symmetry plane is destroyed and the two states can mix. (Adapted from Salem et al., 1975)...

Two orbitals of the oxygen atom have not been involved in the interaction so far, the py orbital and the other spn hybrid. These are transferred to the middle of the diagram unchanged in energy or shape, although, for completeness, they should be redrawn in place they are nonbonding orbitals of the carbonyl group, n 0 and no-... 

Having carefully constructed the interaction diagram for the carbonyl group in Figure 3.21, we must now interpret it. We first make note of the frontier orbitals. 

Figure 3.22. Interaction diagram for the carbonyl group with a proton (the electrostatic effect of the positive charge is ignored).

Figure 8.1. Carbonyl group (a) interaction diagram (b) the active orbitals (note the lower no has been omitted) (c) interaction diagram for a protonated carbonyl.

Epiotis criticized state correlation diagrams because they neglect electronic repulsion and molecular orbital interactions, which may lead to chemical intermediates and energy barriers [39]. These diagrams are also inappropriate to deal with bicentric reactions, like cycloadditions to olefins, which may be initiated by the carbonyl group a or n electrons [40]. 

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