Cyclohexene radical isomers stability

  1. The enthalpies of creating a cyclohexene radical isomers are:

    ORTHO: 444 kJ/mol
    [​IMG]

    META: 361 kJ/mol
    [​IMG]

    PARA: 401 kJ/mol
    [​IMG]

    The meta-isomer is most stable (that is the reason for the formation of meta product in radical addition). Para/meta isomers energies seem obvious - both carbons are equivalent, only the meta-carbon participates in multiple bond, para-carbon doesn't.
    I can't see why the ORTHO-isomer is the least stable one. The (.CR3) radical should rather be more stable than (.CHR2). What do you think?
     

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  2. jcsd
  3. Figured out, the PARA isomer has greater degree of hyperconjugation than ORTHO isomer.
     
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