Formose reaction kinetics

Fig. 7.—Rate of Formose Reaction (Addition Reactions Only) Showing Kinetics of Zero Order in Organic Compounds and First Order in Ca(OH)2 at 60° at Intermediate Levels of Conversion. [Rate of feed of HCHO (mole.liter" .min ) 0—, 0.94 —0.86 —, 0.78 (CHjOH stabilized) —A—, 0.35 —V—, 0.15.]...

The Cannizzaro reaction of formaldehyde is far from a simple kinetic process that could be characterized by first- or second-order kinetics, and that would be a single reaction in which methanol and formate are produced. Rather, it proceeds in alkaline medium in conjunction with the formose reaction, the autocatalytic self-addition of formaldehyde to produce glycolaldehyde, which is then followed by aldol reaction to afford higher aldoses and ketoses. Mono-, di-, tri-, and tetra-valent bases, as well as nitrogenous bases, have been reported to catalyze both reactions homo-... 

The subject of the chemical synthesis of formose sugars, including the historical background, the results of kinetic studies and a rdsumd of biological tests, have been summarized by Mizuno and Weiss.Some chemical aspects of the formose reaction have also been surveyed in Japanese papers." The review " covers the literature up to 1971, which roughly coincides with the period covered in the previous report in this series. In the subsequent years, efforts have been continued to evaluate the influence of various factors affecting the yield and composition of the formose sugars. 

High performance liquid chromatography has been used to study the mechanism and kinetics of the formose reaction. The mechanism proposed is shown in Scheme 1. Previous emphasis on mixed aldol condensations between C2 and C3 fragments is not supported, these providing only minor path way s. °... 

Trioses to Hexoses.- A kinetic analysis of the formose reaction has led to the conclusion that the carbonyl rearrangement and retro-aldol reaction steps play a substantial role in the autocatalytic process. The condensation of D-glyceraldehyde acetonide with racemic alkyl (alkylthiomethyl) sulfoxides proceeded with high selectivity to produce diastereomeric l-alkylsulfinyl-l-alkylthio-3,4-0-isopropylidene-D-tetroses with a predominance of e/yrhro-products. An example is given in... 

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