Threose is a four-carbon monosaccharide with

molecular formula In chemistry, a chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, ...

C₄H₈O₄. It has a terminal

aldehyde In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl grou ...

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-

stereoisomer In stereochemistry, stereoisomerism, or spatial isomerism, is a form of isomerism in which molecules have the same molecular formula and sequence of bonded atoms (constitution), but differ in the three-dimensional orientations of their atoms in ...

s, 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). The prefix "threo" which derives from threose (and "erythro" from a corresponding

diastereomer In stereochemistry, diastereomers (sometimes called diastereoisomers) are a type of stereoisomer. Diastereomers are defined as non-mirror image, non-identical stereoisomers. Hence, they occur when two or more stereoisomers of a compound have di ...

erythrose Erythrose is a tetrose saccharide with the chemical formula C4H8O4. It has one aldehyde group, and is thus part of the aldose family. The natural isomer is D-erythrose; it is a diastereomer of D -threose. Erythrose was first isolated in 1849 ...

) offer a useful way to describe general organic structures with adjacent chiral centers, where "the prefixes... designate the relative configuration of the centers".Formulas Using Other Configurational Notations
W. Rausch, accessed 1 March 2011 As is depicted in a

Fischer projection In chemistry, the Fischer projection, devised by Emil Fischer in 1891, is a two-dimensional representation of a three-dimensional organic molecule by projection. Fischer projections were originally proposed for the depiction of carbohydrates ...

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".Prof. Rausch helpfully notes that the prefixes "may be applied to racemic compounds, as well as pure enantiomers and meso compounds", and that when depicted in the common "zig-zag" representation, adjacent "substituents may lie on the same side of the carbon chain... ynor on opposite sides... nti, which is opposite of their depiction in a

References

{{Carbohydrates Aldotetroses

See also

References