Orbital, anti-bonding

Immediately after the deprotonation from s w-zn-hydroxyphenyl-l, 2-dioxetane, the charge on 0(14)-C6H( is 0.53e and 0(3)-CH is 0.27e.. The HOMO at A in Fig.3 shows that both the a -HOMO and 0 -HOMO are on the phenoxide group. When the reaction proceeds to the transition state B, an electron is transferred to the 03-04 a orbital (anti-bonding) as shown in P -HOMO of B in Fig.3. Going down the potential curve the... 

HOMO of alkene (jc orbital) anti bonding LUMO of anhydride k orbital)... 

Figure 8-5 The Energy Levels of Ethylene Under the PPP-SCE (htraineteTi/iitioii. [ fie tc orbital is bonding and tfie n orbital is anti bon din g.

Effects that arise because one spatial arrangement of electrons (or orbitals or bonds) IS more stable than another are called stereoelectronic effects There is a stereoelec tromc preference for the anti coplanar arrangement of proton and leaving group in E2 reactions Although coplanarity of the p orbitals is the best geometry for the E2 process modest deviations from this ideal can be tolerated In such cases the terms used are syn periplanar and anti periplanar... 

Anti-bonding tt orbital, 293 Atomic orbital resonance, 295 16/3-Azido- 17a-iodoandrostanes, 24 16p-Azido-17a-iodo-5a-androstan-3 -ol acetate, 28... 

The LUMO is similar to the HOMO, but the lobes do not align. Thi> appears more like an anti-bonding orbital. 

The same conclusion may again be reached by considering only the HOMO orbital. Figure 15.24. For the conrotatory path the orbital interaction leads directly to a bonding orbital, while the orbital phases for the disrotatory motion lead to an anti-bonding orbital. 

One-electron oxidation to [Rh2(OCOMe)4(H20)2]+ leads to an ion (violet to orange, depending on solvent) with a shorter Rh-Rh bond (2.317 A) than that in the neutral molecule (2.385 A), suggesting the electron has been removed from an orbital with anti-bonding character. 

In the MO scheme the rhodium atoms use their dxz y2 orbitals to form the Rh—O bonds, the remaining 4d orbitals are used to form four pairs of bonding and anti-bonding MOs (a, 8 and 7r) (Figure 2.37a). 

There is (a) cr-donation from a filled oxygen orbital to an empty platinum orbital and (b) 7r back-bonding from a filled metal d orbital into an empty oxygen 7r -anti-bonding orbital. 

Back-bonding, with formation of a 7r-bond, from a filled metal d orbital to an anti-bonding it -ethene orbital. 

Kasai and McLeod (57, 58) also studied a series of bimetallic diatomics, AgM (M = Mg, Ca, Sr, Be, Zn, Cd, or Hg), by ESR spectroscopy. For all of these species, the hyperfine coupling to the Ag nucleus was found to be isotropic. It was shown that the unpaired electron resides in an orbital resulting essentially from an anti-bonding combination of the valence s orbitals of the Ag and M atoms. A typical spectrum is shown in Fig. 13. 

Jorgensen CK (1975) Partly Filled Shells Constituting Anti-bonding Orbitals with Higher Ionization Energy than Their Bonding Counterparts. 22 49-81 Jorgensen CK (1975) Photo-Electron Spectra of Non-Metallic Solids and Consequences for Quantum Chemistry. 24 1-58... 

The repulsion of the thallium and oxygen lone pairs lead to a distortion of the Tl-6s lone pair, which is no longer totally spherical as one would intuitively expect for an s orbital. The thallium contributions involved in the anti-bonding combination are indeed of 97.7% s-, 1.8% p- and 0.5% d-character. Thus, a much less than expected p-character is found for the thallium orbital, which shows that extensive s-p mixing or hybridization is not essential for the lone pair to become stereochemically active. 

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