What are Enantiomers?

What is an Enantiomer?

Enantiomers can be defined as one of two different stereoisomers of a compound which is the mirror image of the second stereoisomer of that compound. Enantiomers can be classified as specific types of optical isomers. It is important to note that two enantiomers of a compound must be non-superimposable on each other. Therefore, enantiomers can be alternately defined as optical isomers that are non-superimposable mirror images of each other. The presence of a single chiral atom (or a structural feature in a compound that results in something similar) can result in the compound as a whole having two different possible structures, each of which are non-superimposable mirror images of each other. Each of these possible structures can be referred to as an ‘enantiomorph’. The structural property of a chemical compound that allows it to have two different possible enantiomorphs is often referred to as enantiomorphism.

It is also important to note that it is possible for a molecule to have more than one chiral feature. Such molecules are known to possess multiple geometric forms (however, some of these forms may still be perfect mirror images of each other). It can also be noted that when enantiomers are placed in a symmetric environment, the physical and chemical properties of the two enantiomers are almost identical. However, they differ in the directions in which they rotate plane polarized light. For example, if one enantiomer rotates the plane of polarized light to the left, the other enantiomer will rotate the plane of polarized light to the right.

Chemical Nature of Enantiomers

Chemical compounds that exhibit stereoisomerism and have multiple enantiomeric structures are known to often participate in chemical reactions with other enantiomeric compounds. In fact, many biological molecules are known to be enantiomers. Furthermore, it is important to note that two different enantiomers of the same chemical compound can have completely different effects on many organisms. This phenomenon is widely observed in the effects of different drugs on human beings. In most cases, only one of the enantiomers of a drug will have the ability to bring about the desired physiological changes. The other enantiomer of the drug is often not as active. In fact, it is not uncommon for one of the enantiomers of some drugs to have an adverse effect on the health of the organism. This is often the reason why enantiomerically “pure” drugs are often developed in order to control the side effects of the drug.

Frequently Asked Questions on Enantiomer

What are the differences between enantiomers and diastereomers?

An enantiomer can be defined as one of two stereoisomers of a compound that is a non-superimposable mirror image of another stereoisomer of the same compound. On the other hand, a diastereomer is a stereoisomer which has two (or more) stereocenters. Such isomers are not known to be mirror images of each other.

List some examples of enantiomers.

Lactic acid, an organic acid which is also referred to as milk acid, is known to have two enantiomers. The first enantiomer is (S)(+) lactic acid, which is the left enantiomer. The second enantiomer is (R)(-) lactic acid, which is the right enantiomer.

Another compound which is known to have two enantiomers that are mirror images of each other is mecoprop.

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