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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 and used by chemists, particularly in organic chemistry and biochemistry .
Nonetheless, the Fischer projection is a simple way of depicting multiple sequential stereocenters that does not require or imply any knowledge of actual conformation. A Fischer projection will restrict a 3-D molecule to 2-D, and therefore, there are limitations to changing the configuration of the chiral centers.
The D/L system (named after Latin dexter and laevus, right and left), not to be confused with the d-and l-system, see above, does this by relating the molecule to glyceraldehyde. Glyceraldehyde is chiral itself and its two isomers are labeled D and L (typically typeset in small caps in published work). Certain chemical manipulations can be ...
A Fischer projection can be used to differentiate between L- and D- molecules Chirality (chemistry). For instance, by definition, in a Fischer projection the penultimate carbon of D-sugars are depicted with hydrogen on the left and hydroxyl on the right. L-sugars will be shown with the hydrogen on the right and the hydroxyl on the left.
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
In the D/L system, glyceraldehyde is used as the configurational standard for carbohydrates. [7] Monosaccharides with an absolute configuration identical to (R)-glyceraldehyde at the last stereocentre, for example C5 in glucose, are assigned the stereo-descriptor D-. Those similar to (S)-glyceraldehyde are assigned an L-.
Another nomenclature system employed to specify configuration is Fischer convention. [20] This is also referred to as the D- and L-system. Here the relative configuration is assigned with reference to D-(+)-Glyceraldehyde and L-(−)-Glyceraldehyde, being taken as standard. Fischer convention is widely used in sugar chemistry and for α-amino ...
Fischer projection of D-glyceraldehyde. Like most carbohydrates, simple aldoses have the general chemical formula C n (H 2 O) n.Because formaldehyde (n=1) and glycolaldehyde (n=2) are not generally considered to be carbohydrates, [1] the simplest possible aldose is the triose glyceraldehyde, which only contains three carbon atoms.