Haworth reaction mechanism

These conclusions do not comply with the explanation given by Haworth, Hirst and Samuels and by Pacsu for the reaction mechanism of the acid-catalyzed hydrolysis of the rhamnose and turanose orthoesters, respectively. It seems, however, that the experimental data of these authors can be re-interpreted without difficulty, to fit into the picture given for the reaction mechanism of the maltose orthoester. The first and very rapid reaction, which Haworth and coworkers associated with the removal of a methoxyl residue, would, as in the maltose orthoester, involve the rupture of the bond between the central carbon atom and that oxygen atom which is linked to carbon atom 1. This process liberates the 3-form of L-rhamnose substituted at position 2 by a methyl hydrogen orthoacetate residue. However, since this intermediate is... 

HMF has been discovered for the first time in 1895 by Diill and Kiermeyer who independently introduced a method of synthesis of HMF that they named oxy-methylfurfurol [65, 66]. Later, Haworth and Jones studied the mechanism of this reaction and showed that the formation of HMF involved a triple dehydration of hexoses [67]. Other studies performed by Van Dam, Kuster and Antal showed that the dehydration of hexoses (especially fructose and glucose) involved two possible pathways (Scheme 5) [63, 68, 69]. The path 1 involves the dehydration of ring systems (fructopyranose or glucopyranose), while the path 2 is based on acyclic derivatives (glucose and fructose open chain). 

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