04carbrxns

04carbrxns - I.C.i.-1 I.C.i.-2 R e a ctio n s o f M o n o -...

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I.C.i.-1 Reactions of Mono- and Reactions of Mono- and Disaccharides Disaccharides Isomerization glucose fructose mannose Oxidation R-CHO R-COOH R-CH 2 OH R-COOH Reduction sugar sugar alcohols Acetal formation/hydrolysis sugar glycoside Browning reactions O C C HO H OH H 2 OH OH OH H H H H carbonyl group is key need open chain structure I.C.i.-2 Isomerization Isomerization : First step : First step Isomerization is possible because of the “acidity” of the α hydrogen When proton comes off Forms resonance hybrid Relatively stable Electrons shared across two (partial) double bonds O C C HO H OH H 2 OH OH OH H H H H α hydrogen (on C next to carbonyl) O C C C HO OH H 2 OH OH OH H H H H O C C C HO OH H 2 OH OH OH H H H H base
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I.C.i.-3 Isomerization Isomerization : : Enolate Enolate Ion Ion Resonates between two forms (contributing structures) Resonance hybrid called enolate ion O C C C HO OH H 2 OH OH OH H H H H O C C C HO OH H 2 OH OH OH H H H H O C C OH H δ δ I.C.i.-4 Isomerization Isomerization : Two pathways : Two pathways Proton can add back at two locations: O C C C C C C HO OH H 2 OH OH OH H H H H O C C C HO OH H 2 OH OH OH H H H H 1 2 enediol aldehyde O C C C C C C HO OH H 2 OH OH OH H H H H H H O C C C HO OH H 2 OH OH OH H H H H keto enol
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This note was uploaded on 11/03/2010 for the course FST 100A taught by Professor Dungan during the Fall '08 term at UC Davis.

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04carbrxns - I.C.i.-1 I.C.i.-2 R e a ctio n s o f M o n o -...

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