Portland State University. Department of Chemistry
Raymond P. Lutz
Date of Publication
Master of Science (M.S.) in Chemistry
Cope rearrangement, Aluminum oxide, Biphenyl compounds
1 online resource (52 p.)
The alumina-catalyzed Cope rearrangements of meso- and dl-3,4-diphenylhexa-1,5-diene were examined in detail, following up a preliminary observation by H. Berg at Portland State University. Commercial column-chromatography grade alumina was employed, and was further activated before use.by heating at 650-700° for four hours.
Using a ratio of 20 mg of dl-3,4-diphenylhex-l,5-diene to 1 g of alumina in heptane, the Cope rearrangement was complete within 15 minutes at room temperature to give exclusively trans,trans-1,6-diphenylhexa-1,5-diene. This was identified.by melting point, infrared spectroscopy and vapor phase chromatography
The catalyzed rearrangement of meso-3,4-diphenylhexa-l,5-diene was run using the same diene to alumina ratio. It was found that 31% of the meso-diene was converted to cis,trans- and trans,trans-l,6-diphenylhexa-1,5-diene at room temperature in four hours. Product iso-merization appeared to take place; the initial ratio of cis,trans-diene to trans,trans-diene was estimated to be 73:27. Another run was carried out at 60°, where the problem of isomerization of cis,trans-diene to trans,trans-diene was more pronounced. The rearrangement gave cis, trans-diene and trans,trans-diene in a ratio of 58:42, as estimated by extrapolation of the product ratio to zero time. Approximately 95% of meso-diene had reacted in one hour at this temperature. The extent of conversion of mes-diene was calculated by quantitative infrared spectroscopy, and the isomeric distribution of products was determined by vapor phase chromatography.
The product distribution in the alumina-catalyzed rearrangements parallels that of the thermal Cope rearrangement, where dl-diene gives exclusively trans,trans-diene at 80° with a half-life of eight hours and meso-diene gives 63% cis,trans-diene and 27% trans,trans-diene at 120° with a half-life of 15 hours.
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Wang, Paul Jhy-Shing, "Alumina-catalyzed Cope rearrangement" (1974). Dissertations and Theses. Paper 2405.