Glyceraldehyde

Glyceraldehyde (glyceral) 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 glycerol and aldehyde, as glyceraldehyde is glycerol with one alcohol group oxidized to an aldehyde.

Glyceraldehyde
Names
Systematic IUPAC name
2,3-Dihydroxypropanal
Other names
Glyceraldehyde
Glyceric aldehyde
Glyceral
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.000.264
UNII
Properties[1]
C3H6O3
Molar mass 90.078 g·mol−1
Density 1.455 g/cm3
Melting point 145 °C (293 °F; 418 K)
Boiling point 140 to 150 °C (284 to 302 °F; 413 to 423 K) at 0.8 mmHg
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Structure

Glyceraldehyde has one chiral center and therefore exists as two different enantiomers with opposite optical rotation:

  • In the D/L nomenclature, either D from Latin Dexter meaning "right", or L from Latin Laevo meaning "left"
  • In the R/S nomenclature, either R from Latin Rectus meaning "right", or S from Latin Sinister meaning "left"
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 configuration can only be determined from the chemical structure, whereas the optical rotation can only be determined empirically (by experiment).

It was by a lucky guess that the molecular D- geometry was assigned to (+)-glyceraldehyde in the late 19th century, as confirmed by X-ray crystallography in 1951.[2]

Nomenclature

In the D/L system, glyceraldehyde is used as the configurational standard for carbohydrates. Monosaccharides with an absolute configuration identical to (R)-glyceraldehyde at the last stereocentre, for example C5 in glucose, are assigned the stereo-descriptor D-. Those similar to (S)-glyceraldehyde are assigned an L-.

Chemical synthesis

Glyceraldehyde can be prepared, along with dihydroxyacetone, by the mild oxidation of glycerol, for example with hydrogen peroxide and a ferrous salt as catalyst. Dihydroxyacetone, the simplest ketose, is an isomer of glyceraldehyde.

Biosynthesis

The enzyme glycerol dehydrogenase (NADP+) has two substrates, glycerol and NADP+, and 3 products, D-glyceraldehyde, NADPH and H+.

Biochemical role

The interconversion of the phosphates of glyceraldehyde (glyceraldehyde 3-phosphate) and dihydroxyacetone (dihydroxyacetone phosphate), catalyzed by the enzyme triosephosphate isomerase, is an important intermediate step in glycolysis.

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See also

References
  1. Merck Index, 11th Edition, 4376
  2. Determination of the Absolute Configuration of Optically Active Compounds by Means of X-Rays Nature 168, 271-272 J. M. BIJVOET, A. F. PEERDEMAN & A. J. van BOMMEL doi:10.1038/168271a0

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