Hiickel rule hydrocarbons


The Hiickel rule predicts aromaticity for the six-7c-electron cation derived from cycloheptatriene by hydride abstraction and antiaromaticity for the planar eight-rc-electron anion that would be formed by deprotonation. The cation is indeed very stable, with a P Cr+ of -1-4.7. ° Salts containing the cation can be isolated as a product of a variety of preparative procedures. On the other hand, the pK of cycloheptatriene has been estimated at 36. ° This value is similar to those of normal 1,4-dienes and does not indicate strong destabilization. Thus, the seven-membered eight-rc-electron anion is probably nonplanar. This would be similar to the situation in the nonplanar eight-rc-electron hydrocarbon, cyclooctatetraene.  [c.526]

One of molecular orbital theories early successes came m 1931 when Erich Huckel dis covered an interesting pattern m the tt orbital energy levels of benzene cyclobutadiene and cyclooctatetraene By limiting his analysis to monocyclic conjugated polyenes and restricting the structures to planar geometries Huckel found that whether a hydrocarbon of this type was aromatic depended on its number of tt electrons He set forth what we now call Huckel s rule  [c.451]


Advanced organic chemistry Ч.1 (2000) -- [ c.0 ]