Ch_322a_10.015

Ch_322a_10.015 - Combustion of Alkanes The reaction of...

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Combustion of Alkanes The reaction of alkanes with oxygen in a flame is complex. While all the details are not known, it seems that the initial steps involve formation of peroxy radicals . initiation R-H + O O : . . . . R . + H-O-O . alkyl radical hydroperoxy radical propagation (1) R . + O O . . . . R-O-O . alkylperoxy radical (2) R-O-O . R-H + R-O-O -H alkyl hydroperoxide + R . Both propagating steps are energetically favorable. Step (1) is similar to a radical-radical recombination reaction. In step (2), a stronger O-H bond (~110 kcal/mol) replaces a weaker C-H bond (96-99 kcal/mol).
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The alkyl hydroperoxides rapidly decompose by homolysis of the relatively weak peroxy bond (35-40 kcal/mol): R-O-O : -H R-O . H-O . + alkoxy radical hydroxy R-O-H H-O-H + + R . R . These initiating reactions in combustion describe the process called autoxidation.
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Ch_322a_10.015 - Combustion of Alkanes The reaction of...

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