difference between enantiomers and diastereomers
Difference Between Enantiomers and Diastereomers
Enantiomers and diastereomers are stereoisomers. Here, we, at Buzzle, have undertaken an enantiomer vs. diastereomers comparison to highlight the differences between the two.
Enantiopure Drug
It is a drug that has only one enantiomeric form of the active ingredient. These drugs have greater efficacy and fewer side effects. In some cases, other enantiomeric of the drug may have adverse effects.Enantiomers Vs. Diastereomers
Definition
✸ Enantiomers are stereoisomers that are non-superimposable mirror images of each other. Organic compounds containing a chiral carbon that have the same structural as well as chemical formula but are non-superimposable on each other and are mirror images of each other, are nothing but enantiomers.
✸ Diastereomers are stereoisomers that are non-superimposable, non-mirror images of each other. Organic compounds with two or more chiral carbon that have the same structural and molecular formula; these compounds are, however, non-superimposable and non-mirror images of each other.
✸ Here, all the stereocenters (chiral carbons) of one stereoisomer differs in orientation from the stereocenters of the other stereoisomer.
✸ Here, only some stereocenters (chiral carbons) of one stereoisomer differs in orientation from the stereocenters of the other stereoisomer.
Example
✸ In 2-bromo-3-chloro-butane, depicted below, both chiral carbons are either in the R, R or the S, S configuration. The two structures thus shown are exact mirror images of each other with both bromine and chlorine in the same side of the carbon-carbon bond.
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✸ In the same compound depicted below, the chiral carbon atoms are either in the R, S configuration or the S, R configuration. Here the bromine and chlorine atoms are at the opposite sides of the carbon-carbon bond.
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Properties
✸ Enantiomers of a compound have the same physical properties except optical activity, but differ in chemical properties.
✸ Diastereomers of a compound differ in their physical as well as chemical properties.
Number of Stereocenters
✸ A compound with one or more stereocenters (chiral carbons) is capable of enantiomerism (property to form enantiomers).
✸ A compound needs at least two stereocenters (chiral carbons) in order to form diastereomers.
Optical Activity
Optical activity is the physical property of an asymmetric carbon compound to rotate the plane of the linearly polarized light.
✸ All enantiomers show optical activity. When they rotate light in the clockwise direction, they are known as dextrorotary, (+) or d, and when they rotate light in the anticlockwise direction, they are known as levorotary, (-) or l. When a compound contains equal number of d and l molecules, they render the compound optically inactive and are called a race mixture.
✸ Not all diastereomers are optically active. Some stereoisomers are said to be meso compounds and seem to be optically inactive despite having two or more chiral carbons. The compounds possess a line of symmetry, meaning, one half of the compound is identical to the other half, but these two halves differ in their orientation (if one half has S configuration then the other half has R configuration).