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Allylic strain

Allylic strain or 1,3-allylic strain in organic chemistry and its associated strain energy results from an unfavorable molecular conformation for the allyl group. The simplest representative of the allyls, propene, in its ground state has the methyl C-H bond eclipsed with the carbon carbon double bond. When this bond is pointing away the resulting unfavorable conformation is called bisected.

The activation energy for rotating around the allyl CC bond is 1.98 kcal/mol[1].

This type of strain also extends to carbonyls.


  1. ^ Conformational analysis. LXIV. Calculation of the structures and energies of unsaturated hydrocarbons by the Westheimer methodNorman L. Allinger, Jerry A. Hirsch, Mary Ann Miller, and Irene J. Tyminski J. Am. Chem. Soc.; 1968; 90(21) pp 5773 - 5780; doi:10.1021/ja01023a021
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Allylic_strain". A list of authors is available in Wikipedia.
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