Hydrogen bonding orbitals

Cyclopropane belies its simple appearance. Hybridization of the carbon-hydrogen bonding orbitals in cyclopropane is close to sp (actually sp ) and that of the orbitals forming the carbon-carbon bonds is sp It was proposed that these latter orbitals lie outside the line connecting adjacent carbon atoms such that the angle between the axes of the sp hybridized orbitals is 104°. The CCC internuclear angles are clearly 60° and so the carbon-carbon bonds are bent by 22°. 

The hybridization of the carbon-hydrogen bond orbitals in cyclopropane is clearly similar to those in alkenes. However, the chemical shifts of these two types of proton are appreciably different and factors other than hybridization must be responsible. 

In addition, there are n boron-hydrogen bonding orbitals involved in the a bonds between these atoms on the outside of the cluster. Adding these to the n + 1 bonding orbitals in the central core gives a total of 2 + 1 bonding orbitals overall in the cluster. 

Since the hydrogen bonding orbital is a Is orbital, a thermal reaction will follow the suprafacial route if k is odd, and the antarafaciai route if k is even e.g. 

Section 2 6 Bonding m methane is most often described by an orbital hybridization model which is a modified form of valence bond theory Four equiva lent sp hybrid orbitals of carbon are generated by mixing the 2s 2p 2py and 2p orbitals Overlap of each half filled sp hybrid orbital with a half filled hydrogen Is orbital gives a ct bond... 

Each carbon in propane is bonded to four atoms and is sp hybridized The C—C bonds are a bonds involving overlap of a half filled sp hybrid orbital of one carbon with a half filled sp hybrid orbital of the other The C—H bonds are a bonds involving overlap of a half filled sp hybrid onbital of carbon with a half filled hydrogen li orbital... 

FIGURE 2.9 Each half-filled sp orbital overlaps with a half-filled hydrogen Is orbital along a line between them giving a tetrahedral arrangement of four a bonds. Only the major lobe of each sp orbital is shown. Each orbital contains a smaller back lobe, which has been omitted for clarity. 

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