Threose

Threose is a four-carbon monosaccharide with molecular formula C₄H₈O₄. It has a terminal aldehyde group, rather than a ketone, in its linear chain and so is considered part of the aldose family of monosaccharides. The threose name can be used to refer to both the d- and l-stereoisomers and more generally to the racemic mixture (d/L-, equal parts D- and L-) as well as to the more generic threose structure (absolute stereochemistry unspecified).

Threose^[1]

d-Threose
l-Threose
Names
IUPAC names d-Threose l-Threose [2]
Systematic IUPAC name (2S,3R)-2,3,4-Trihydroxybutanal (d) (2R,3S)-2,3,4-Trihydroxybutanal (l)
Other names Threotetrose
Identifiers
CAS Number	95-43-2 (d) Y 95-44-3 (l) Y
3D model (JSmol)	(d): Interactive image (l): Interactive image
ChEBI	CHEBI:28587 Y
ChemSpider	388736 Y
ECHA InfoCard	100.002.199
PubChem CID	439665 (d)
UNII	4EHO9A06LX (d) Y MHH79K1BVR (l) Y
CompTox Dashboard (EPA)	DTXSID101017421
InChI InChI=1S/C4H8O4/c5-1-3(7)4(8)2-6/h1,3-4,6-8H,2H2/t3-,4-/m1/s1 Y Key: YTBSYETUWUMLBZ-QWWZWVQMSA-N Y InChI=1/C4H8O4/c5-1-3(7)4(8)2-6/h1,3-4,6-8H,2H2/t3-,4-/m1/s1 Key: YTBSYETUWUMLBZ-QWWZWVQMBY
SMILES (d): O=C[C@@H](O)[C@H](O)CO (l): OC[C@H](O)[C@@H](O)C=O
Properties
Chemical formula	C4H8O4
Molar mass	120.104 g·mol−1
Appearance	Syrup
Solubility in water	Very soluble[vague]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

The prefix "threo-" which derives from threose (and "erythro-" from a corresponding diastereomer erythrose) offer a useful way to describe general organic structures with adjacent chiral centers, where "the prefixes... designate the relative configuration of the centers".^[3] As is depicted in a Fischer projection of d-threose, the adjacent substituents will have a syn orientation in the isomer referred to as "threo", and are anti in the isomer referred to as "erythro".^[3][4]

Fischer projections depicting the two enantiomers of threose

Although often inconsequential, threose in aqueous solution mainly exists as the hydrate owing to the following equilibrium:^[5]

HOCH₂CH(OH)CH(OH)CHO + H₂O ⇌ HOCH₂CH(OH)CH(OH)CH(OH)₂

See also

• Threitol
• Threonic acid
• Threose nucleic acid