It-antibonding orbital

The it antibonding orbital of ethylene (and other olefins) is a also a proper MO, highly localized to the two carbon atoms. It is the linear combination of the two 2p orbitals which is A with respect to reflection in the bisecting plane and S w.r.t. a 180° rotation about the C2 axis which contains that plane. 

Figure 11.1 (a) The ethylene it bonding orbital is symmetric (S) with respect to reflection in the mirror plane a, and antisymmetric (A) with respect to reflection in the mirror plane a, (b) The ethylene it antibonding orbital is antisymmetric (A) with respect to reflection in both a and a. ... 

Fig. I. Spin-orbital diagram of the different states of oxygen. The x and y refer to the two perpendicular it antibonding orbitals of oxygen. On the right this diagram depicts the real wave-functions for the...

Figure 8 shows a mechanism for this reaction. Under these conditions since nickelocene has two unpaired electrons in its antibonding orbitals, it may be attacked by ethylene, releasing the cyclopentadienyl rings and... 

Nucleophilic addition reactions occur by electron donation from the nucleophile to the IT antibonding orbital of the ketone. If the faces of the ketone are different, addition happens faster at the more accessible orbital lobe. Use SpartanView to display mesh electron-density surfaces of 2-norbomanone and camphor, and simultaneously display the tt antibonding orbital (LUMO) surface of each. Which face of each ketone is more reactive What is the stereochemistry of the alcohol produced by reaction of each with NaBH4 ... 

The over-all process of addition is to a first approximation an electronic rearrangement. One electron jumps from the bond between the metal and alkyl into the depressed 2 orbital. This is followed by the formation of a new bond between alkyl radical and the nearest carbon atom of the olefin. At the moment of alkyl migration, the olefin is a pseudo-radical because of the extra electron in its antibonding orbital. 

It is not surprising, therefore, that alkyl group-transition metal linkages are usually less stable than those between transition metals and the ir electron donors which possess the it antibonding orbitals. It is less obvious, however, why alkyls of transition metals should in general be less stable than... 

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