In order to obtain chemical evidence concerning the configuration of free alkyl radicals, 1-(carbo-t-butylperoxy)-cis- and trans-1,4-dimethylcyclohexane and exo- and endo-2-(carbo-t-butylperoxy)-2-methylnorbornane have been synthesized, and their decomposition rates and products determined.
The cis- and trans-cyclohexyl peresters undergo thermal decomposition at 60° in cumene at essentially the same rates (cis isomer ∆H⁺ = 27.5 kcal/ mole, ∆S⁺ = 5.07 eu; trans isomer ∆H⁺ = 27.8 kcal/mole, ∆S⁺ = 5.75 eu) and with direct formation of 1,4-dimethylcyclohexyl radicals, carbon dioxide, and t-butoxy radicals. The products, cis- and trans-1,4-dimethylcyclohexane, 1,4-dimethylcyclohexene, and 4-methylmethylenecyclohexane, formed from the 1,4-dimethylcyclohexyl radicals in degassed cumene, are the same from both precursors. In the presence of oxygen in 1,2-dimethoxyethane (glyme) or 25 ml Freon TF:1 ml glyme, both the cis and trans peresters gave identical yields (after reduction) of trans-1,4-dimethylcyclohexanol (58%) and cis-1,4-dimethylcyclohexanol (42%) at oxygen pressures from 1 to approximately 600 atm. A common intermediate is thus indicated.
In cumene at 75°, exo-2-(carbo-t-butylperoxy)-2-methylnorbornane decomposes 6.6 - 6.7 times faster than its endo isomer. The activation parameters are ∆H⁺ = 27.9 kcal/mole, ∆S⁺ = 6.31 eu, and ∆H⁺ = 30.3 kcal/mole, ∆S⁺ = 9.33 eu, respectively. The products, exo- and endo-2-methylnorbornane, 2-methyl-2-norbornene, and 2-methylenenorbornane, resulting from 2-methyl-2-norbornyl radicals in degassed cumene, are essentially the same from either isomeric source. The same ratio of exo- to endo-2-methyl-2-norbornyl hydroperoxide (15%:85%) is formed from either perester in the presence of oxygen at pressures up to -600 atm.
Unlike the apparently unique case of distinctly different cis- and trans-9-decalyl radicals, the alkyl radicals from the decomposition of isomeric norbornyl and cyclohexyl peresters have a single configuration or they invert much faster than they react with oxygen. The results suggest that if radicals with a stereochemical "memory" of their origin exist in these systems, their lifetimes are of the order of 10⁻¹⁰ seconds or less.
For the 1,4-dimethylcyclohexyl radical, hydrogen atom transfer and reaction with oxygen were found to occur preferentially (82% and 58%, respectively) from an axial direction. On the other hand, cumene and oxygen react with the 2-methyl-2-norbornyl radical predominantly from an exo direction (90% and 85%, respectively).
The carbonylation of tetrahydrolinalool, and several synthetic routes to 1-alkyl-4-t-butylcyclohexanecarboxylic acids also have been explored. / Science, Faculty of / Chemistry, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/37509 |
| Date | January 1969 |
| Creators | Schindel, Wesley Gerald |
| Publisher | University of British Columbia |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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