Glyceraldehyde

From Free net encyclopedia

Glyceraldehyde is a triose monosaccharide with chemical formula C₃H₆O₃. It is the simplest of all common aldoses. It is a sweet colorless crystalline solid that is an intermediate compound in carbohydrate metabolism. The word comes from combining glycerine and aldehyde, as glyceraldehyde is merely glycerine with one hydroxide changed to an aldehyde.

Glyceraldehyde has a chiral centre and therefore exists in two different conformations with opposite steriochemical rotation:

(R from Latin rectus meaning upright), or steriochemically (D for dextrorotory, meaning Right)
(S from Latin sinister meaning left), or steriochemically (L for levorotory, meaning Left)

While the optical rotation of glyceraldehyde is (+) for dextrorotory and (-) for levorotory, this is not true for all monosaccharides. The steriochemical rotation can be intuitively determined by the chemical structure, whereas the optical rotation can only be determined empirically.

Monosaccharides with an identical conformation at the anomeric carbon to (R)-glyceraldehyde are assigned the stereo-descriptor D, those similar to (S)-glyceraldehyde are assigned a L. Both, D and L, should be small capital letters.

Glyceraldehyde can be prepared, along with dihydroxyacetone, by the mild oxidation of glycerol, for example with hydrogen peroxide and a ferrous salt as catalyst.

It was by a lucky guess that the D molecular geometry was assigned to (+)-glyceraldehyde in the late 19th century, as confirmed by x-ray crystallography in 1951.

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