Bulletin of the Korean Chemical Society

Korean Chemical Society (대한화학회)
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$^{13}C-NMR$ Study of the Applicaton of the “ Tools of Increasing Electron Demand ” to the 8-Aryl-tricyclo $[3.2.1.0^{2,7}]$oct-8-yl Cations

  • Published : 1991.04.20
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Abstract

The $^{13}C-NMR$ shifts of a series of para-substituted $8-aryl-tricyclo[3.2.1.0^{2,7}]oct-8-yl$ and $9-aryl-tricyclo[3.3.1.0^{2,8}]-non-9-yl$ cations were measured in $FSO_3H/SO_2ClF\ at\-90^{\circ}$ in order to examine whether the ${\rho}^{C^+}$ values can be used as a measure of the geometric influence on the charge delocalization resulting from ${\rho}$ conjugation in rigid tricyclopropylcarbinyl cations. Plot of the ${\Delta}{\delta}^{C+} shifts against the ${\sigma}^{C+}$ constants revealed excellent linear correlation. The 8-aryl tricyclooctyl systems yielded a ${\rho}^{C+}$ value of -5.00 with r = 0.9962. Previous investigation of the 9-aryl-tricyclononyl systems gave a correlation coefficient of r = 0.9948 with a slope of ${\rho}^{C+}$ = -4.95. A fair parallelism exists between the results of $^{19}F-NMR $ studies and the change of ${\rho}^{C+}$ value in these cations. Consequently, it is established that the ${\rho}^{C+}$ value can be used to explain the mechanism of charge stabilization of the rigid cyclopropylcarbinyl cation such as tricyclo $[3.2.1.0^{2,7}]oct-8-yl$ cation.

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