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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 10, Number 2
BKCSDE 10(2)
February 20, 1989 

 
Title
19F NMR Studies on 8,9-Dehydro-2-adamantyl and 2,4-Dehydro-5-homoadamantyl Cations
Author
Jaechul Shim, Ghilsoo Nam, Kyongtae Kim, Jung-Hyu Shin*
Keywords
Abstract
To probe the geometrical effects of cyclopropyl moiety on the stabilization of an adjacent cation center, 19F 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 19F chemical shift of 8,9-dehydro-2-adamantyl cation 3 and that of 2,4-dehydro-5-adamantyl cation 4 is 5.1 ppm (Δ Δδ). 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-Relationship8 on the basis of 19F chemical shift.
Page
132 - 133
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