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Diradical Wells, IX. Stereochemistry of Cyclopropane Ring Opening: The Case of 1,1‐Difluoro‐2,3‐diphenylcyclopropane
Author(s) -
Roth Wolfgang R.,
Wasser Thorsten,
Boenke Martin
Publication year - 1997
Publication title -
liebigs annalen
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0947-3440
DOI - 10.1002/jlac.199719970707
Subject(s) - conrotatory and disrotatory , diradical , racemization , isomerization , chemistry , cyclopropane , ring (chemistry) , activation energy , computational chemistry , photochemistry , stereochemistry , atomic physics , organic chemistry , physics , catalysis , excited state , singlet state
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.