Abstract

Hydrothermal organic transformations under geochemically relevant conditions can result in complex product mixtures that form via multiple reaction pathways. The hydrothermal decomposition reactions of the model ketone dibenzyl ketone form a mixture of reduction, dehydration, fragmentation, and coupling products that suggest simultaneous and competitive radical and ionic reaction pathways. Here we show how Norrish Type I photocleavage of dibenzyl ketone can be used to independently generate the benzyl radicals previously proposed as the primary intermediates for the pure hydrothermal reaction. Under hydrothermal conditions, the benzyl radicals undergo hydrogen atom abstraction from dibenzyl ketone and para-coupling reactions that are not observed under ambient conditions. The photochemical method allows the primary radical coupling products to be identified, and because these products are generated rapidly, the method also allows the kinetics of the subsequent dehydration and Paal-Knorr cyclization reactions to be measured. In this way, the radical and ionic thermal and hydrothermal reaction pathways can be studied separately.

Original languageEnglish (US)
Pages (from-to)7861-7871
Number of pages11
JournalJournal of Organic Chemistry
Volume79
Issue number17
DOIs
StatePublished - Sep 5 2014

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Geochemistry
Photochemical reactions
Ketones
Dehydration
Cyclization
Hydrogen
Decomposition
Atoms
Kinetics

ASJC Scopus subject areas

  • Organic Chemistry

Cite this

Hydrothermal photochemistry as a mechanistic tool in organic geochemistry : The chemistry of dibenzyl ketone. / Yang, Ziming; Lorance, Edward D.; Bockisch, Christiana; Williams, Lynda; Hartnett, Hilairy; Shock, Everett; Gould, Ian.

In: Journal of Organic Chemistry, Vol. 79, No. 17, 05.09.2014, p. 7861-7871.

Research output: Contribution to journalArticle

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abstract = "Hydrothermal organic transformations under geochemically relevant conditions can result in complex product mixtures that form via multiple reaction pathways. The hydrothermal decomposition reactions of the model ketone dibenzyl ketone form a mixture of reduction, dehydration, fragmentation, and coupling products that suggest simultaneous and competitive radical and ionic reaction pathways. Here we show how Norrish Type I photocleavage of dibenzyl ketone can be used to independently generate the benzyl radicals previously proposed as the primary intermediates for the pure hydrothermal reaction. Under hydrothermal conditions, the benzyl radicals undergo hydrogen atom abstraction from dibenzyl ketone and para-coupling reactions that are not observed under ambient conditions. The photochemical method allows the primary radical coupling products to be identified, and because these products are generated rapidly, the method also allows the kinetics of the subsequent dehydration and Paal-Knorr cyclization reactions to be measured. In this way, the radical and ionic thermal and hydrothermal reaction pathways can be studied separately.",
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AU - Hartnett, Hilairy

AU - Shock, Everett

AU - Gould, Ian

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