11.6 The r Molecular Orbitals of benzene FIGURE 11.3(a) The framework of bonds shown in the tube model of benzene are o bonds. b)Each carbon ybridized and has a 2p orbital perpendicular to the o framework. Overlap of the 2p orbitals generates a system encompa ne entire ring. (c) Electrostatic potential plot of benzene. the red area in the center corresponds to the region above and he plane of the ring where the t electrons are concentrated 11.5 AN ORBITAL HYBRIDIZATION VIEW OF BONDING IN BENZENE The structural facts that benzene is planar, all of the bond angles are 120, and each car bon is bonded to three other atoms, suggest sp- hybridization for carbon and the frame work of g bonds shown in Fi In addition to its three sp- hybrid orbitals, each carbon has a half-filled 2p orbital that can participate in T bonding. Figure 11.3b shows the continuous TT system that encompasses all of the carbons that result from overlap of these 2p orbitals. The six TT electrons of benzene are delocalized over all six carbons The electrostatic potential map of benzene(Figure 113c) shows regions of high electron density above and below the plane of the ring, which is where we expect the most loosely held electrons(the T electrons) to be 11.6 THE TT MOLECULAR ORBITALS OF BENZENE The picture of benzene as a planar framework of o bonds with six electrons in a delo- calized T orbital is a useful, but superficial, one. Six electrons cannot simultaneously occupy any one orbital, be it an atomic orbital or a molecular orbital. A more rigorous molecular orbital analysis recognizes that overlap of the six 2p atomic orbitals of the ring carbons generates six T molecular orbitals. These six T molecular orbitals include three which are bonding and three which are antibonding. The relative energies of these orbitals and the distribution of the a electrons among them are illustrated in figure 114. Benzene is said to have a closed-shell Tr electron configuration. All the bonding orbitals are filled, and there are no electrons in antibonding orbitals. FIGURE 11.4 molecular orbitals f be Antibonding zene arranged in order of in- orbitals easing energy. The six T electrons of benzene occup bitals, all of which are bond- 两2+ I3 Bonding ing. The nodal properties of x these orbitals may be viewed on Learning By Modeling Back Forward Main MenuToc Study Guide ToC Student o MHHE Website11.5 AN ORBITAL HYBRIDIZATION VIEW OF BONDING IN BENZENE The structural facts that benzene is planar, all of the bond angles are 120°, and each car￾bon is bonded to three other atoms, suggest sp2 hybridization for carbon and the frame￾work of bonds shown in Figure 11.3a. In addition to its three sp2 hybrid orbitals, each carbon has a half-filled 2p orbital that can participate in bonding. Figure 11.3b shows the continuous system that encompasses all of the carbons that result from overlap of these 2p orbitals. The six electrons of benzene are delocalized over all six carbons. The electrostatic potential map of benzene (Figure 11.3c) shows regions of high electron density above and below the plane of the ring, which is where we expect the most loosely held electrons (the electrons) to be. 11.6 THE MOLECULAR ORBITALS OF BENZENE The picture of benzene as a planar framework of bonds with six electrons in a delo￾calized orbital is a useful, but superficial, one. Six electrons cannot simultaneously occupy any one orbital, be it an atomic orbital or a molecular orbital. A more rigorous molecular orbital analysis recognizes that overlap of the six 2p atomic orbitals of the ring carbons generates six molecular orbitals. These six molecular orbitals include three which are bonding and three which are antibonding. The relative energies of these orbitals and the distribution of the electrons among them are illustrated in Figure 11.4. Benzene is said to have a closed-shell electron configuration. All the bonding orbitals are filled, and there are no electrons in antibonding orbitals. 11.6 The  Molecular Orbitals of Benzene 405 (a) (b) (c) Antibonding orbitals Energy Bonding orbitals π4 π2 π1 π3 π5 π6 FIGURE 11.3 (a) The framework of bonds shown in the tube model of benzene are bonds. (b) Each carbon is sp2 - hybridized and has a 2p orbital perpendicular to the framework. Overlap of the 2p orbitals generates a system encompassing the entire ring. (c) Electrostatic potential plot of benzene. The red area in the center corresponds to the region above and below the plane of the ring where the electrons are concentrated. FIGURE 11.4 The molecular orbitals of ben￾zene arranged in order of in￾creasing energy. The six electrons of benzene occupy the three lowest energy or￾bitals, all of which are bond￾ing. The nodal properties of these orbitals may be viewed on Learning By Modeling. Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website