Page 324 - Mechanism and Theory in Organic Chemistry
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Carbonium Ions  31 1

      96c), two car,bons are tetracoordinated; the third participant in the three-center
      bond  is  hydrogen.  Figure  6.17  shows  an  orbital  diagram  of  Structure  96a.



























                                                        ..........
                                                     H&H ..   : H
                                                     H
                                                          'H'








      In the product-determining step of Scheme 6, the nucleophilic oxygen of water
      attacks one of the carbons; this carbon then withdraws its orbital from the three-
      center bond  and an ordinary  u bond  is  formed  between  the remaining carbon
      and the hydrogen.
          Another  mechanism, that shown in Scheme 7, has also been suggested for
      the  label  scrambling  of  Equation  6.44.  In  each  of  the  corner-protonated  cyclo-
      profianes (96a-97c),  all three  participants in  the  three-center  bond  are carbon.
















      Figure 6.17 Orbital picture of edge-protonated cyclopropane.
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