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The Electrocyclic Cyclopropyl-Allyl Rearrangement. Preliminary communication

✍ Scribed by E. Haselbach

Publisher
John Wiley and Sons
Year
1971
Tongue
German
Weight
225 KB
Volume
54
Category
Article
ISSN
0018-019X

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✦ Synopsis

MINDO-2 SCF calculations indicate that ring-opening of cyclopropyl radical (I) to allyl radical ( ) is more favourable via a disrotatory reaction path, the calculated activation energy being -30 kcal/mole. (For conrotatory opening the activation energy was found to be -44 kcallmole.) The two critical motions of the nuclei during the transformation are found to be strongly decoupled, i. e. rupture of the CH,-CH, bond precedes rotation of the CH, groups. As predicted by qualitative theories both ring-opening modes are unfavourable since they involve a changc in electronic ground-state symmetry between I and 11. The preferred ring-opening mode is discussed qualitatively in terms of Evans' principle.

3,

A recent determination of the heat of formation of tropenyl radical has yielded an empirical resonancc energy for this [4n+ 31 system (n = 1) of -30 kcal/mole 1171; i . e . only slightly less than that of benzene (-36 kcal/mole [18]).

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