Periodate-hypobromite oxidation

Oxidation. Citric acid is easily oxidized by a variety of oxidizing agents such as peroxides, hypochlorite, persulfate, permanganate, periodate, hypobromite, chromate, manganese dioxide, and nitric acid. The products of oxidation are usually acetonedicarboxyhc acid (5), oxaUc acid (6), carbon dioxide, and water, depending on the conditions used (5). 

An aqueous solution of sulfuric acid and a salt of periodic add, trisodium paraperiodate, or one of the potassium periodates, has been used frequently as a substitute for pure periodic add. When the product of the oxidation reaction is to be isolated, the effect of the presence of metal ions on the yield should be considered. If the product is volatile or slightly soluble, or is isolated either as a slightly soluble derivative or by extraction with organic solvents, the presence of metal ions should not reduce the yield. In the Case of certain methylhexosides34 which were oxidized by periodic acid formed from potassium metaperiodate and an equivalent of sulfuric add in aqueous solution, the presence of potassium ions was found to cause a low yield of the crystalline strontium salt prepared by the strontium hypobromite oxidation of the dialdehyde resulting from the periodic add reaction. Oxidation by pure periodic add, a solution of which is prepared either from crystalline paraperiodic add or by the previously mentioned method from potassium metaperiodate, is desirable when the presence of difficultly removed metal ions affects the yield adversely. 

Monocrotaline (45) was reduced (LiAlH4) to 2,3,4-trimethylpentane-l,2,3,5-tetraol (46). Periodate oxidation of (46), followed by hypobromite oxidation of the product, afforded 3-hydroxy-2-methylpropanoic acid, whose hydrazide (48) was shown to be enantiomeric with the known hydrazide" of -configuration. The hydrazide from monocrotaline therefore has the S-configuration and monocrotalic acid has the R-configuration at C-4. 

Oxidation of 1 mol of the anomeric methyl aldopentopyranosides with 2 mol of periodate or lead tetraacetate yields one of a pair of dialdehydes, a dextrorotatory product 48 being derived from a-D- or p-L-glycosides and levo-rotatory 49 from p-D or a-L isomers. In turn, hypobromite oxidation affords either dicarboxylic acid 47 or 50. Additional possibilities for configurational correlation accrue from the fact that a methyl aldotetrofuranoside similarly yields 48 or 49, whereas a methyl aldopentofuranoside gives 44 or 45 as the final product. 

In alkaline solutions, iodine can be oxidized to iodate by sodium hypochlorite or hypobromite, whereas chlorine passed into a solution of iodine and alkah oxidizes ah the way to periodate. 

Alicyclic hydroxamic acids undergo several specific oxidative cleavage reactions which may be of diagnostic or preparative value. In the pyrrolidine series compounds of type 66 have been oxidized with sodium hypobromite or with periodates to give y-nitroso acids (113). Ozonolysis gives the corresponding y-nitro acids. The related cyclic aldonitrone.s are also oxidized by periodate to nitroso acids, presumably via the hydroxamic acids.This periodate fission was used in the complex degradation of J -nitrones derived from aconitine. 

In the synthesis of 1,6-anhydro-D-glucitol, at least, a 2,6-anhydride is a byproduct.53 Its structure was assigned on the basis of its i.r. spectrum, in comparison with those of the 1,6- and 1,5-anhydro-D-glucitols, and the fact that no diglycolic acid was obtained after periodate oxidation followed by oxidation with hypobromite. 

In 1873, it was first reported that cellulose that has been oxidized with chromic acid or potassium permanganate is weakened in alkaline solutions, and several years later these findings were confirmed. By 1899, it was known that cellulose that had been oxidized with nitric acid, or bromine in the presence of calcium carbonate, afforded oxidized celluloses from which D-glucoisosaccharinates were formed on suitable treatment with lime-water.Hydrocelluloses, alkaline-hypobromite oxycelluloses, and alkaline-hypochlorite oxycelluloses have no internal, alkali-sensitive links. Cellulose oxidized with neutral hypochlorite, acidic hypochlorite, potassium dichromate and sulfuric acid, potassium dichromate and oxalic acid, periodic acid, or metaperiodate gives products which are alkali-sensitive. Periodic acid oxycellulose and metaperiodate oxycellulose are much more alkali-sensitive than the others. ... 

Jackson and Hudson obtained a dicarboxylic acid (104), isolated as its crystalline strontium salt, in a yield of 20% by oxidizing methyl a-n-mannopyranoside in an aqueous solution of barium hypobromite. This acid, which is normally obtained by oxidation of the dialdehyde obtained by periodate oxidation of the n-glucoside, is most probably another example of a product arising from the cleavage of a bond between adjacent keto groups. Heyns found that changing the pH, in the catalytic oxidation of benzyl S-n-arabinop3Tanoside, to pH 7.3 resulted in the formation of a dicarboxylic acid (105) (isolated as its crystalline barium salt) in 42% yield. He considered this to be a further oxidation product of the 4-keto compound normally formed. 

Matsumura [185-188] has oxidized a wide range of polysaccharides, starch, xyloses, amyloses, pectins, and the like with hypochlorite/periodate. The products are either biodegradable at low oxidation levels or functional at high oxidation levels the balance has not yet been established for commercial success. Other than Matsumura, van Bekkum and co-workers, at Delft University, has been the major player in the search to control the hypochlorite/periodate liquid-phase oxidations of starches [189-191]. He has been searching for catalytic processes to speed up the oxidation with hypochlorite. Hypobromite is a more active oxidant than hypochlorite but more expensive, however, it may be generated in situ from the cheap hypochlorite and bromide ion in one solution [191, 192]. This is shown in Scheme 16. 

The formation of this colored ion may be used as a spot test for periodate (Procedure I). Alternatively, the interference by periodate, with the catalytic effect of copper salts on the reaction between Mn+ ion and hypobromite may be utilized (Procedure II). This reaction normally proceeds with formation of manganese dioxide but, in the presence of even extremely small amounts of copper salts, permanganate is formed instead. The activation of the hypobromite is due to the intermediate formation of Cu oxide, which causes a further oxidation from MnOj to Mn04 ion, with regeneration of Cu oxide (see page 300). The formation of the stable complex ion of tervalent copper with periodate prevents the activation of the hypobromite. 

---