Structure
Glyceraldehyde has 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"
| 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).
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.
Read more about this topic: Glyceraldehyde
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