Bulletin of the Korean Chemical Society

Korean Chemical Society (대한화학회)
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$^{19}$F NMR Studies on 8,9-Dehydro-2-adamantyl and 2,4-Dehydro-5-homoadamantyl Cations

  • Shim, Jae-Chul (Department of Chemistry, Seoul National University) ;
  • Nam, Ghil-Soo (Department of Chemistry, Seoul National University) ;
  • Kim, Kyong-Tae (Department of Chemistry, Seoul National University) ;
  • Shin, Jung-Hyu (Department of Chemistry, Seoul National University)
  • Published : 1989.04.20
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Abstract

To probe the geometrical effects of cyclopropyl moiety on the stabilization of an adjacent cation center, chemical shift of 2-p-fluorophenyl-8,9-dehydro-2-adamantyl cation (3) was compared with that of 5-p-fluorophenyl-2,4-dehydro-5-homoadamantyl cation (4). Difference between the chemical shift of 8,9-dehydro-2-adamantyl cation 3 and that of 2,4-dehydro-5-adamantyl cation 4 is 5.1 ppm (${\Delta}{\Delta}{\delta}$). We conclude, therefore, that ion 3 is about 3.82 kcal more stadble than ion 4 of which rigid carbon skeleton requires significant distortion of the cyclopropane ring from the ideal bisected conformation. The energy difference between these cations can be calculated by Taft-Relationship$^8$ on the basis of chemical shift.

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