On the mechanism of thermally assisted hydrolysis and methylation of carbohydrates: the contribution of aldol and retroaldol reactions

摘要

The thermally assisted hydrolysis and methylation (THM) analysis of glycolaldehyde produces a series of methylated C3 to C6 metasaccharinic acids by aldol reactions. The contribution of aldol and retro aldol reactions was investigated by analysis of 1-~(13)C-glycolaldehyde, 1-~(13)C-glucose, and 6-~(13)C-glucose. It could be shown that carbohydrates undergo retro aldol cleavage under strong alkaline conditions, as they are in THM, and that these cleavage products subsequently produce higher molecular weight condensation products by aldol reactions. The cleavage occurs more readily close to the reducing end of the carbohydrate and recombination of these fragments may account for up to 30% of the saccharinic acid products formed.