The Norbornenyl-Nortricyclyl Radical System

Author: Fujimoto, Ted Tsutomu

Year: 1967

Degree: Bachelor's thesis

Advisor: Roberts, John D.

Committee Member: Unknown, Unknown

Option: Chemistry

DOI: 10.7907/dn0a-xe08

Abstract

The reduction of rortricyclyl and endo-norbornenyl bromides by tri-n-butyltine hydride has been used for the generation of the norbornenyl-nortricyclyl radical system. Utilizing the tri-n-butyltin hydride to also trap the radicals before full equilibration, a linear correlation of the ratio of product nortricyclene/ product norbornene to the hydrogen donor concentration has been obtained. Observation of this predicted linear relationship, and also of the predicted reciprocal correspondence of the intercepts associated withe linear plots obtained by initiating the radical system from the nortricyclyl bromide and from the endo-norbornenyl bromide, indicate that only classical norbornenyl and nortricyclyl radicals need be invoked. However, the existence of a product forming "nonclassical" species can not yet be ruled out.

Several investigation have been reported which attempted to determine if the "nonclassical" free rad1cal analogous to the "nonclassical" carbonium ion appeared as a reaction intermediate in the norbornenyl-nortricycly1 system. The norbornenyl radicals have been generated by the decarbonylation of norborn-2-en-5-yl carboxaldehyde1 ; from the norborn-2-en-5-yl carboxy radica12,3; by the addition of thiols to norbornadiene4-6 along with arenesulfonyl halides7, and other substances4. The conclusion of these studies has been that delocalization of the unpaired electron by participat5on of the neighboring double bond does not contribute to the nature of the free radical intermediate. However, in none of these investigations has the radical intermediates been generated from both norbornenyl and nortricyclyl derivatives.

An independent investigation using tri-n-butyltin hydride to generate the norbornenyl-nortricyclyl radicals was inconclusive, and the results did not provide an answer to whether a single "nonclassical" intermediate or a pair of classical radicals were involved in the reaction mechanism. No effective trapping of the radicals was reported in this investigation.

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