W2013CHM2311 Part 4c Notes

6 ev 129 ev 2px b3u 2 52 ev 2py b2u 1 52

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Unformatted text preview: -1 -1 1 1 -1 -1 Rz, xy B2g B3g 1 1 -1 -1 1 -1 -1 1 1 1 -1 -1 1 -1 -1 1 Ry, xz Rx, yz Au 1 1 1 1 -1 -1 -1 -1 B1u 1 1 -1 -1 -1 -1 1 1 z B2u B3u 1 1 -1 -1 1 -1 -1 1 -1 -1 1 1 -1 1 1 -1 y x x O C Assigning Symmetry Labels to the Group Orbitals for CO2 O z y In ­Phase Combina0ons D2h E C2(z) C2(y) C2(x) i σ(xy) σ(xz) σ(yz) ϕA + ϕB 1 2p px + px pz + pz s + s 2s F H F  ­1 1  ­1  ­1 1  ­1 1 1  ­1  ­1 1  ­1 p 2 1 1  ­1 1 py + py 1 1 1 1 1 1 1 1 1 1 1 1 2s 1 1 1 F H F x O C Assigning Symmetry Labels to the Group Orbitals for CO2 O z y D2h E C2(z) C2(y) C2(x) i Out ­of ­Phase Combina0ons σ(xy) σ(xz) σ(yz) ϕA - ϕB 1  ­1  ­1 1 1  ­1  ­1 1 1  ­1 1  ­1 1  ­1 1  ­1 1 1  ­1  ­1  ­1  ­1 1 1 1 1  ­1  ­1  ­1  ­1 1 1 F H F py  ­ py 2p px  ­ px pz  ­ pz 2s s  ­ s F H F x O C Assigning Symmetry Labels to the Group Orbitals for CO2 O z y In ­Phase Combina0ons Out ­of ­Phase Combina0ons ϕA - ϕB ϕA + ϕB 1 = B2u 5 = B3g 2p 2 = B3u 2p 3 = Ag 2p 6 = B2g 7 = B1u 4 = Ag 2s 8 = B1u s 2 2s F H F F HFF H F F H F Assigning Symmetry Labels to the Atomic Orbitals of Carbon in CO2 In order to determine which GOs interact with which AOs on carbon, the symmetry labels of the atomic orbitals on carbon must be assigned. These can be obtained directly from the D2h character table, so it is not necessary to derive the irreducible representa0ons: s px pz py Determining Orbital Interac0ons If two orbitals have the same symmetry labels they will interact provided that they are close enough in energy. Orbital Carbon Oxygen 2s  ­19.5 eV  ­32.4 eV ➜  GOs 4 & 8 2p  ­10.7 eV  ­15.9 eV ➜  GOs 1 ­3 & 5 ­7 Orbital Interac3ons in CO2 C AO Symmetry GO Energy 2s Ag 3 & 4 3.6 eV & 12.9 eV 2px B3u 2 5.2 eV 2py B2u 1 5.2 eV 2pz B1u 7 & 8 5.2 eV & 21.7 eV Determining Orbital Interac0ons Therefore, there are four allowed interac0ons: ↳  whenever two AOs (or one AO with one GO) interact, they generate one bonding and one an0bonding MO. ↳  since carbon 2s can interact with two GOs of oxygen (3 and 4), there must be three MOs that result from this combina0on of three AOs. The remaining orbitals (the ones that do not interact) become nonbonding orbitals ↳  GOs 5, 6, and 8 Orbital Interac3ons in CO2 C AO Symmetry GO Energy 2s Ag 3 & 4 3.6 eV & 12.9 eV 2px B3u 2 5.2 eV 2py B2u 1 5.2 eV 2pz B1u 7 & 8 5.2 eV & 21.7 eV See Fig. 5 ­26, p.157 in Mi...
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This note was uploaded on 03/28/2014 for the course CHM 2311 taught by Professor Richardson during the Winter '09 term at University of Ottawa.

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