Formaldehyde periodate oxidation

In theory, periodate oxidation could have given a clear-cut answer as to the composition of the isomeric mixture of deoxy ribose phosphates. The 4-phosphate (73), devoid of vicinal diol groups, should be resistant to periodate the 3-phosphate (74) should reduce one and only one molar equivalent of the oxidant and yield one molar equivalent of both formaldehyde and the phosphorylated dialdehyde (75), whereas the 5-phosphate (76) could be expected to reduce one molar equivalent of periodate relatively rapidly, followed by a slower overoxidation reaction owing to the oxidation of malonaldehyde, formed as a result of the glycol cleavage. 

Since aldehydes are very common amongst periodate-oxidation products, analysis for them has been well developed and widely used. Most emphasis has been placed on methods for the assay of formaldehyde, as this is the most common product. Formaldehyde was first determined (in periodate work) by an oxidation method.2 47 66... 

The early addition of Dimedon is reported234 to depress the formation of hexamethylenetetramine from formaldehyde in the presence of ammonia. O Dea282 found that the activated methylene center, sometimes formed in periodate oxidations of carbohydrates, reacts appreciably with the formaldehyde formed, thus giving low yields of apparent formaldehyde. He was able to depress this side reaction by the use of lowered temperatures and by the addition of benzaldehyde or of p-hydroxybenzaldehyde. The analyses for formaldehyde have often been more successful at a pH of 7.5 than at lower pH values.57, 68 59a 60 264... 

Finally, French and Mclntire studied the periodate oxidation of alpha, beta, and gamma dextrin, found that neither formic acid nor formaldehyde was produced, and concluded that all three have a cyclic structure, as earlier proposed by Freudenberg. Also supported was the gamma dextrin structure proposed by Freudenberg, on the basis of acid... 

On periodate oxidation, open-chain (1— 4)-linked polysaccharides yield one molecule of formic acid from the nonreducing end and two molecules of formic acid, as well as one molecule of formaldehyde, from the reducing end. 

The hexitols may be determined quantitatively by periodate oxidation. Either the amount of oxidant consumed or the amount of acid or formaldehyde liberated may be determined. This method will not... 

When applied to N-acylglycofuranosylamines, the periodate oxidation showed an abnormal uptake of oxidant ( overoxidation ). For example, when oxidized with lead tetraacetate12 and with periodate,1065 N-acetyl-a-D-glucofuranosylamine (15) afforded formaldehyde (indicating a furanose structure), and it consumed more than 5 moles of oxidant per mole. This result can be attributed to subsequent oxidation of the formic acid produced,69 or to the formation,10 by hydrolysis, of the intermediate 2-hydroxypropanedial (tartron-aldehyde) (77) that would then be oxidized. This tendency to undergo overoxidation has been found common for the furanoid N-acyl-gly cos y lam ines.24,25... 

This is in marked contrast to the higher aldehydes which oxidize much more readily, at temperatures as low as 100° C.—e.g., acetaldehyde (55). The mechanism by which formaldehyde reduces the induction period in hydrocarbon oxidation below 300° C. is not evident. An inhibiting effect is explicable on the basis of removal of free radicals, as Lewis and von Elbe (32) have pointed out. This could occur by CH20 -f R — RH -f HCO. HCO is then oxidized to the relatively inert CH03 which diffuses to the wall and is destroyed. Above 300° C. formaldehyde is oxidized more rapidly, giving rise to free radicals, and it is not surprising to find that the induction period in some hydrocarbon oxidations is shortened. 

The slower conversion of the anomerized D-glucofuranosides into D-gluco-pyranosides was studied with a higher concentration, of acid. The concentration of furanosides was followed by determining the amount of formaldehyde formed by periodate oxidation. It was concluded that the same acyclic ion (16) is formed from both furanoid anomers, and that ring closure gives a mixture of pyranosides similar to that found in the equilibrium mixture of pyranosides. 

In contrast to the relatively simple polyxylose of Bishop,141 the polyxylose prepared by Mora nd examined by Dutton and Unrau1 7-1 9 was extremely complex. Its facile depolymerization1 7 during the early stages of hydrolysis with 0.1 N hydrochloric acid suggested the presence of D-xylofuranosyl residues. Periodate oxidation resulted in the consumption of 0.01 mole of oxidant per molecular equivalent of sugar residue, indicating the presence of periodate-resistant residues. Formaldehyde was also liberated this was believed to arise from acyclic D-xylosc residues unsubstituted at C-4 and C-5. 

These treatments convert to ionic substances, and remove, nearly all constituents of natural materials the acid treatments release any inositol present as phosphate, or combined in phospholipids, glycosides, etc. Glycerol remains in the deionized sample, but it can be oxidized separately, or be removed by heat decomposition or by repeatedly evaporating the solution to dryness. Such polyhydric alcohols of greater chain length as erythritol and mannitol, when present, would still interfere. However, corrections can be made for these compounds by determining the formaldehyde which they form on periodate oxidation, or they may be removed by chromatography on filter paper. The micro-periodate method is well suited to the analysis of samples eluted from filter paper, provided that care is exercised to remove the tiny particles of cellulose which are usually found in such eluates. 

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