TY - JOUR
T1 - Hydrothermal photochemistry as a mechanistic tool in organic geochemistry
T2 - The chemistry of dibenzyl ketone
AU - Yang, Ziming
AU - Lorance, Edward D.
AU - Bockisch, Christiana
AU - Williams, Lynda
AU - Hartnett, Hilairy
AU - Shock, Everett
AU - Gould, Ian
N1 - Publisher Copyright:
© 2014 American Chemical Society.
PY - 2014/9/5
Y1 - 2014/9/5
N2 - 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.
AB - 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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U2 - 10.1021/jo500899x
DO - 10.1021/jo500899x
M3 - Article
AN - SCOPUS:84924308723
SN - 0022-3263
VL - 79
SP - 7861
EP - 7871
JO - Journal of Organic Chemistry
JF - Journal of Organic Chemistry
IS - 17
ER -