Catalytic effect of aluminium chloride on the example of the conversion of sugar model compounds

• AlCl3 combines the catalytic properties of Brønsted bases and acids.
• AlCl3 catalyzes isomerisation, dehydration and benzilic-acid-rearrangement.
• Glycolaldehyde is mainly converted to 2-hydroxybut-3-enoic acid, if AlCl3 is used.

In this work, the catalytic effect of the Brønsted acid hydrochloric acid, the Brønsted base sodium hydroxide and the Lewis acid AlCl3 on the conversion of biomass derived carbohydrates is investigated. On the example of the glycolaldehyde conversion, it is shown that the Lewis acid catalyses the ketol-endiol-tautomerism, the dehydration, the retro-aldol-reaction and the benzilic-acid-rearrangement. The main products are C4- and C6-carbohydrates as well as their secondary products 2-hydroxybut-3-enoic acid 1 and several furans. Under the same reaction conditions hydrochloric acid catalyzes mainly the dehydration and sodium hydroxide the tautomerism and subsequent aldolization.

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