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Erythrose is a tetrose saccharide with the chemical formula C 4 H 8 O 4. 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. [3] Fischer projections depicting the two enantiomers of erythrose
Two older prefixes still commonly used to distinguish diastereomers are threo and erythro. In the case of saccharides, when drawn in the Fischer projection the erythro isomer has two identical substituents on the same side and the threo isomer has them on opposite sides. [ 7 ]
Threose is a four-carbon monosaccharide with molecular formula C 4 H 8 O 4.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.
Arthur Cayley was probably the first to publish results that consider molecular graphs as early as in 1874, even before the introduction of the term "graph". [4] For the purposes of enumeration of isomers, Cayley considered "diagrams" made of points labelled by atoms and connected by links into an assemblage.
The penultimate step in Zhang & Trudell's classic epibatidine synthesis is an example of epimerization. [4] Pharmaceutical examples include epimerization of the erythro isomers of methylphenidate to the pharmacologically preferred and lower-energy threo isomers, and undesired in vivo epimerization of tesofensine to brasofensine .
For octahedral complexes of formula MX 4 Y 2, two isomers also exist. (Here M is a metal atom, and X and Y are two different types of ligands .) In the cis isomer, the two Y ligands are adjacent to each other at 90°, as is true for the two chlorine atoms shown in green in cis -[Co(NH 3 ) 4 Cl 2 ] + , at left.
A simple example of cis–trans isomerism is the 1,2-disubstituted ethenes, like the dichloroethene (C 2 H 2 Cl 2) isomers shown below. [7] Dichloroethene isomers. Molecule I is cis-1,2-dichloroethene and molecule II is trans-1,2-dichloroethene.
Its strange that this decription of the definition of a diastereomer does not mention E/Z alkene isomers!--175.38.163.188 18:26, 15 August 2013 (UTC) Cis–trans isomerism does not involve chirality. So the E and Z forms are isomers, but not enantiomers, and as such can't be diastereomers either.