Enthalpies of Formation of cis- and trans-l,2-Diethylcyclopropane and cis- and trans-Bicyclo[6.1.0]nonane. Structural Effects on Energies of Cyclopropane Rings

Kenneth B. Wiberg, Elmer C. Lupton, David J. Wasserman, Arinin de Meijere, Steven R. Kass

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Abstract

The enthalpies of formation of cis- and trans-1,2-diethylcyclopropane were determined by oxygen bomb calorimetry. The cis-diethyl isomer was 1.1 kcal/mol less stable than the trans isomer. Alkyl groups were found to stabilize a cyclopropane ring by the same amount as for a carbon-carbon double bond. The enthalpies of formation cis- and trans-bicyclo[6.1.0]nonane also were determined by oxygen bomb calorimetry. The two bicyclo[6.1.0]nonanes have essentially the same enthalpies of formation, in contrast to cis- and trans-cyclooctene. The introduction of a trigonal center makes the trans-bicyclononane 3 kcal/mol less stable than the cis isomer. Molecular mechanics calculations are reported for a series of cis- and trans-bicyclo[n.1.0]alkanes. In order to better estimate the strain energy of trans-bicyclo[4.1.0]heptane, the difference in energy between it and its cis isomer was calculated via ab initio molecular orbital theory.

Original languageEnglish (US)
Pages (from-to)1740-1744
Number of pages5
JournalJournal of the American Chemical Society
Volume106
Issue number6
DOIs
StatePublished - Mar 1 1984

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