Reactivity studies in water on the acid-catalysed dehydration of psicose compared to other ketohexoses into 5-hydroxymethylfurfural

The conversion of the four possible ketohexoses (fructose, tagatose, sorbose and psicose) into 5-hydroxymethylfurfural (HMF) was explored in water using sulphuric acid as the catalyst (33 mM H2SO4, 120 °C). Significant differences in reactivity were observed and tagatose (48% conversion after 75 min...

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Published in:Carbohydrate research Vol. 446-447; pp. 1 - 6
Main Authors: van Putten, Robert-Jan, van der Waal, Jan C., de Jong, Ed, Heeres, Hero J.
Format: Journal Article
Language:English
Published: Netherlands Elsevier Ltd 29.06.2017
Subjects:
5-Hydroxymethylfurfural
Catalysis
catalysts
fructose
Fructose - chemistry
Furaldehyde - analogs & derivatives
Furaldehyde - chemistry
Hydrogen-Ion Concentration
hydroxymethylfurfural
Ketose
methanol
Methanol - chemistry
Psicose
sorbose
Sugar dehydration
sulfuric acid
tagatose
Water - chemistry
Sugar dehydration
Psicose
5-Hydroxymethylfurfural
Ketose
ISSN:0008-6215, 1873-426X, 1873-426X
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Summary:The conversion of the four possible ketohexoses (fructose, tagatose, sorbose and psicose) into 5-hydroxymethylfurfural (HMF) was explored in water using sulphuric acid as the catalyst (33 mM H2SO4, 120 °C). Significant differences in reactivity were observed and tagatose (48% conversion after 75 min) and psicose (35% conversion after 75 min) were clearly more reactive than fructose and sorbose (around 20% conversion after 75 min). The selectivity to HMF was found to be higher for fructose and psicose than for tagatose and sorbose. 2-Hydroxyacetylfuran (HAF) was shown to be a by-product for mainly sorbose and tagatose (as high as 2% yield). The results indicate that the relative orientation of the hydroxyl groups on C3 and C4 has a major effect on the reactivity and selectivity. This suggests that the dehydration towards HMF takes place via a mechanism with cyclic intermediates in which the C3C4 bond is fixed in a ring structure. A reaction mechanism involving a bicyclic structure is proposed to explain the formation of HAF. The reactivity of the sugars was significantly lower in water than previously observed in methanol. [Display omitted] •Hydroxyl group orientation on C3 and C4 determines ketose reactivity in dehydration.•This suggests a reaction mechanism with cyclic intermediates.•Psicose would be the most favourable substrate for HMF production.•The orientation of the C4 hydroxyl is key in 2-hydroxyacetylfuran formation.•The reactivity of psicose and tagatose affects their application as sweeteners.
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ISSN:0008-6215
1873-426X
1873-426X
DOI:10.1016/j.carres.2017.04.009