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Diradical Wells, IX. Stereochemistry of Cyclopropane Ring Opening: The Case of 1,1-Difluoro-2,3-diphenylcyclopropane

✍ Scribed by Roth, Wolfgang R. ;Wasser, Thorsten ;Boenke, Martin

Publisher: John Wiley and Sons
Year: 1997
Tongue: English
Weight: 398 KB
Volume: 1997
Category: Article
ISSN: 0947-3440
DOI: 10.1002/jlac.199719970707

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✦ Synopsis

Abstract

From the O~2~‐dependence of the trapping rate of 1,1‐difluoro‐2,3‐diphenylcyclopropane in supercritical CO~2~ in the temperature range 110–180°C and the rates of its geometrical isomerization and racemization of the trans‐isomer, the energy profile for the geometrical isomerization is derived. Assuming that 7 is a common intermediate, the temperature dependence of the ratio of the rates of isomerization/racemization leads to a lowering of 1.2 kcal · mol^−1^ for the activation energy for the disrotatory cyclization of the intermediate diradical compared to the conrotatory mode. The energy barriers associated with cyclization of the diradical amount to 2.1 and 0.9 kcal · mol^−1^, respectively.

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