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Conformational Barriers in Medium-Sized Rings. I. trans-Cyclodecene-1,2,4,4,9,9-d_6

Binsch, Gerhard and Roberts, John D. (1965) Conformational Barriers in Medium-Sized Rings. I. trans-Cyclodecene-1,2,4,4,9,9-d_6. Journal of the American Chemical Society, 87 (22). pp. 5157-5162. ISSN 0002-7863. doi:10.1021/ja00950a031.

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The peculiar conformational situation in trans-cycloalkenes of medium ring size is discussed. It is concluded that one pair of optical isomers should exist in the odd-membered rings and two such pairs in the even-membered rings. For a given ring size, the various isomers are expected to be separated from one another by a substantial energy barrier. Cope and co-workers have shown previously that, for trans-cyclooctene, at least one of the barriers is high enough to allow isolation of two very stable optical isomers. Optically active trans-cyclononene was found to be much less stable and transcyclodecene gave no detectable optical activity. In the present investigation, the n.m.r. spectrum of transcyclodecene-1,2,4,4,9,9-d_6 has been studied as a function of temperature. Two processes which are slow on the n.m.r. time scale at low temperatures have been discovered. One of them, which involves rotation of the trans-alkene group through the loop formed by the methylene groups, was found to have an activation energy ΔE^* = 10.7 ± 0.3 kcal/mole and a frequency factor A = 10^(11.7±0.3) sec^(-1). The other process, for which no accurate rates could be determined, appears to involve restricted rotation of the C-6-C-7 molecular segment in the cyclodecene ring.

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Additional Information:© 1965 American Chemical Society. Received April 26, 1965. Supported in part by the National Science Foundation and the Office of Naval Research.
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Office of Naval Research (ONR)UNSPECIFIED
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Caltech Gates and Crellin Laboratories of Chemistry3242
Issue or Number:22
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Official Citation:Conformational Barriers in Medium-Sized Rings. I. trans-Cyclodecene-1,2,4,4,9,9-d6 Gerhard Binsch and John D. Roberts Journal of the American Chemical Society 1965 87 (22), 5157-5162 DOI: 10.1021/ja00950a031
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:61164
Deposited On:16 Oct 2015 17:53
Last Modified:10 Nov 2021 22:45

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