Consider 1,2,3,4,5,8‐hexahydronaphthalene:


If one equivalent of ozone is added, then which double bond will undergo ozonolysis?

If it attacks the more electron rich one, then unstable 10 membered ring will form, and if it attacks the other,less sterically hindered one, stable 6 membered ring having 2 branched aldehydes will form.

What will actually happen? What factors decide this?

  • $\begingroup$ I would be interested to know how you propose to add 1eq of ozone. I suspect the less hindered double bond is likely to be attacked preferentially, but with such a reactive species as ozone I think you'll get a mixture as there is insufficient difference between the two double bonds. $\endgroup$
    – Waylander
    May 21 '19 at 9:06
  • $\begingroup$ @Waylander Since addition of ozone is electrophilic addition, shouldn't it be added to the more electron rich one? Also, the carbon under consideration is sp2 Hybridised, so attack from above and below is not hindered much. $\endgroup$
    – user226375
    May 21 '19 at 9:25
  • $\begingroup$ There is not enough difference between the electron densities of the two bonds IMHO, $\endgroup$
    – Waylander
    May 21 '19 at 9:29
  • $\begingroup$ @Waylander Then will hyperconjugation play a role? The left bond on ozonolysis produces an alkene having more hyperconjugating structures. $\endgroup$
    – user226375
    May 21 '19 at 10:14
  • 1
    $\begingroup$ The rate of epoxidation with MCPBA increases with the degree of alkyl substitution so the central double bond will react preferentially. ifasonline.com/chemicalScience_topic15.jsp MCPBA is a much more controllable reagent than ozone. $\endgroup$
    – Waylander
    May 21 '19 at 13:09

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