Ethene bent-bond description

Overlap of sp hybrid orbitals in the bent bond description of ethene. 

Pauling s prediction that the use of the molecular structure are in better agreement with the bent bond description than with the a,n description. Figure 1.35(a) shows calculated contour lines of a carbon orbital in a plane that is perpendicular to the molecular plane of ethene, and Figure 1.35(b) shows contour lines for an orbital in a plane containing the carbon atoms of cyclopropane. Clearly, much of the orbital lies outside the intemuclear bond line in each case. It is generally agreed that the bonds in cyclopropane are bent the picture from this theoretical calculation reinforces Ae view that they are bent in ethene also. 

A much older description of ethene is known as the bent bond formulation. The double bond is described as the result of overlap of two sp hybrid orbitals on each of the two carbon atoms, as shown in Figure 1.29. This model also predicts that ethene should be a planar molecule, but it predicts H-C-H bond angles of 109.5°— which is even further from the observed 117° than was the prediction based on sp hybridization. Furthermore, except for cyclopropane, we feel imcomfortable about drawing molecular pictures with bonds that... 

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