Accession Number : AD0462329

Title :   CONFORMATIONAL BARRIERS IN MEDIUM-SIZED RINGS. I. TRANS-CYCLODECENE-1,2,4,4,9,9-D6.

Descriptive Note : Technical rept.,

Corporate Author : CALIFORNIA INST OF TECH PASADENA GATES AND CRELLIN LABS OF CHEMISTRY

Personal Author(s) : Binsch, Gerhard ; Roberts, John D.

Report Date : APR 1965

Pagination or Media Count : 28

Abstract : The peculiar conformational situation in transcycloalkenes of medium rign 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 trans-cyclodecene gave no detectable optical activity. In the present investigation, the n.m.r. spectrum of trans-cyclodecene1,2,4,4,0-d6 was studied as a function of temperature. Two processes which are slow on the n.m.r. time scale at low temperatures were 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 of 10.7 = 0.3 kcal/mole and a frequency factor of 10 to the 11.7 = 0.3 power cycles/sec. The other process for which no accurate rates could be determined, appears to involve restricted rotation of the C6H7 molecular segment in the cyclodecene ring. (Author)

Descriptors :   (*ALKENES, MONOCYCLIC COMPOUNDS), (*MOLECULAR ROTATION, MONOCYCLIC COMPOUNDS), (*MONOCYCLIC COMPOUNDS, MOLECULAR PROPERTIES), DEUTERIUM COMPOUNDS, MOLECULAR ISOMERISM, NUCLEAR MAGNETIC RESONANCE, HEAT OF ACTIVATION, MOLECULAR STRUCTURE, CHEMICAL BONDS.

Distribution Statement : APPROVED FOR PUBLIC RELEASE