Monosaccharides Wohl degradation

Much of the chemistry of monosaccharides is the familiar chemistry of alcohols and aldehydes/ketones. Thus, the hydroxyl groups of carbohydrates form esters and ethers. The carbonyl group of a monosaccharide can be reduced with NaBH4 to form an alditol, oxidized with aqueous Br2 to form an aldonic acid, oxidized with HNO3 to form an aldaric acid, oxidized enzymatically to form a uronic acid, or treated with an alcohol in the presence of acid to form a glycoside. Monosaccharides can also be chain-lengthened by the multistep Kiliani-Fischer synthesis and can be chain-shortened by the Wohl degradation. 

The Ruff degradation and the Wohl degradation both cleave the carbonyl-bearing carbon from a monosaccharide to form a new monosaccharide of one fewer carbon. The Nef reaction adds one carbon to a monosaccharide to form a new monosaccharide, as does the Fischer-Kiliani synthesis. 

A D-aldopentose is oxidized by nitric acid to an optically active aldaric acid. A Wohl degradation of the aldopentose leads to a monosaccharide that is oxidized by nitric acid to an optically inactive aldaric acid. Identify the D-aldopentose. 

There are various methods of degrading monosaccharides to the next lower member of the series. Wohl (1893) devised a method which is virtually the reverse of the cyanhydrin ascent since it consists in the removal of hydrocyanic acid from the acetylated nitrile (CXLI) formed on acetylation... 

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