Antibonding a*-molecular

The ketone receives an electron in the antibonding -rr molecular orbital to form it anion radical that is transformed into a (—C—Cl) particle by an intramolecular electron transfer to the antibonding a molecular orbital of the —C—Cl bond. The (—C—Cl)-bond then fragments to form a chloride ion and the corresponding radical (Scheme 8-2). 

Just as bonding and antibonding a molecular orbitals result from the combination of two s atomic orbitals in H2 (Section 1.6), so bonding and antibonding tt molecular orbitals result from the combination of two p atomic orbitals in ethylene. As shown in Figure 1.17, the n bonding MO has no node between nuclei and results from combination of p orbital lobes with... 

Figure 1.1. Representation of the geometry and energy of the bonding and antibonding ( a) molecular orbitals formed by covalent bonding between the Is atomic orbitals of two H atoms, A and B. The probability function, indicates electron density along the internuclear A-B axis.

Figure 1.9. A schematic representation of the formation of bonding (o) and antibonding (a ) molecular orbitals of hydrogen (Hj) by the combination of two equivalent Is hydrogen atomic orbitals. The signs (+) and (-) do not refer to charges but rather to the sign of the wave function /, whose square (t f ) gives the probabiUty of finding the electron(s) in the volume shown.

FIGURE 2.7 The formation of a carbon-hydrogen bond through the overlap of an s/> hybrid orbital with a hydrogen It atomic orbital. Note the formation of both the bonding (o) molecular orbital and the antibonding (a ) molecular orbital. 

Fig. 2.5 Schematic representations of (a) the bonding (cr ) and (b) the antibonding (a ) molecular orbitals in the H2 molecule. The H nuclei are represented by black dots. The red orbital lobes could equally well be marked with a -I- sign, and the blue lobes with a — sign (or vice versa) to indicate the sign of the wavefunction. (c) More realistic representations of the molecular orbitals of H2, generated computationally using Spartan 04, Wavefunction Inc. 2003.

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