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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 ]
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.
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.
The stereoisomers β-D-glucopyranose and β-D-mannopyranose are epimers because they differ only in the stereochemistry at the C-2 position.The hydroxy group in β-D-glucopyranose is equatorial (in the "plane" of the ring), while in β-D-mannopyranose the C-2 hydroxy group is axial (up from the "plane" of the ring).
The compound with the formula (C 5 H 5) 2 Fe 2 (CO) 4 exists as three isomers in solution. In one isomer the CO ligands are terminal. When a pair of CO are bridging, cis and trans isomers are possible depending on the location of the C 5 H 5 groups. [7] Another example in organometallic chemistry is the linkage isomerization of ...
Erythorbic acid (isoascorbic acid, D-araboascorbic acid) is a stereoisomer (C5 epimer) of ascorbic acid (). [1] It is synthesized by a reaction between methyl 2-keto-D-gluconate and sodium methoxide.
Very often, cis–trans stereoisomers contain double bonds or ring structures. In both cases the rotation of bonds is restricted or prevented. [4] When the substituent groups are oriented in the same direction, the diastereomer is referred to as cis, whereas when the substituents are oriented in opposing directions, the diastereomer is referred to as trans.
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.