Cycloalkene density

If the E parameters corresponded to the internuclear angle at C-1, the order of decrease we would expect to be 4 > 5 > 2 however, the actual sequence is 4 > 2 > 5. This has been explained by the different effects of the x andy components of the spin densities on the a orbital at C-1 > 12). From the E / D value it was concluded that all cycloalkene-carbenes have angles which are large compared to the internuclear angle at C-1 thus all the bonds at C-1 should be bent, i. e. C-1 should not be in the ring plane > i > 12). This suggests that 4 is almost planar i >, allowing delocalization of the electron. The electronic state of 1 has not been studied yet. 

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