Glyceraldehyde

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 center and therefore exists as two different enantiomers with opposite optical rotation:

• R from Latin rectus meaning right, or
• S from Latin sinister meaning left

Name of enantiomer	D-glyceraldehyde (R)-glyceraldehyde (+)-glyceraldehyde	L-glyceraldehyde (S)-glyceraldehyde (−)-glyceraldehyde
Fischer projection
Skeletal formula
Ball-and-stick model

While the optical rotation of glyceraldehyde is (+) for R and (−) for S, this is not true for all monosaccharides. The stereochemical rotation can only be determined by the chemical structure, whereas the optical rotation can only be determined empirically (by experiment).

Glyceraldehyde is used as the configurational standard for carbohydrates. Monosaccharides with an identical conformation at the last stereocentre, for example, C5 for glucose, 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.

See also

• Stereoisomerism

References

• Merck Index, 11th Edition, 4376.

Further reading

• Chin. Chem. Soc., Vol. 48(9) 283 (1999) On the Assignment of Anomeric Configuration (pdf)