Learn What Enantiomers are with Proper Examples with the Help of Experts
Chemistry is a fascinating subject where you will find infinite knowledge and brilliant facts to study. Some will amaze you and encourage you to learn more. One such concept of organic chemistry that baffles students the most is enantiomers. These are exceptional organic compounds with a unique characteristic to follow. Enantiomers are the same in chemical structure but differ in molecular orientation. A couple of organic substances, that are similar in every other aspect, are mirror images to each other. They cannot be superimposed but can be considered as laterally inverted images. Isn’t that wonderful?
Let us study more about this brilliant topic and get a little deeper. To make this part of organic chemistry easier to understand, the Chemistry experts at Vedantu have developed a concept page where you will find simplified enantiomers definition and examples to follow and understand. Read on to find the answer to your queries. You can use this concept page as a reference while studying this genre of organic compounds and clear your doubts.
What are Enantiomers?
There is no need to worry when Vedantu is here to clear the doubts. This type of organic substance is similar in terms of chemical and physical nature. Also, the number of atoms of the elements present in the chemical formula is the same. The only thing that varies is their orientation. They are chemically identical and have the same properties. It is just that the same molecule has been laterally inverted to form another molecule.
If all the physical and chemical properties are the same, how can we find out the difference between the two enantiomers? Now that is a valid question that can take anyone by surprise. To answer this question, you need to follow the concept page and study the enantiomers properly. While studying, you will find out that a pair of such substances can only be differentiated by projecting a polarized light on them. The light will be rotated in a particular direction. Based on that direction, one enantiomer is called Dextro (+ or d) and the other one rotating the polarized light in the other direction is called Levo (+ or l). The term ‘rotatory’ is added after Dextro or Levo to coin these optical isomers.
When both the enantiomers are present in the same concentration in a solution, it is called a racemic mixture. This mixture has no optical activity as both the compounds’ power to rotate polarized light are nullified by each other. If you study the enantiomers definition and examples properly on this page, you will understand the concept well.
Properties of Enantiomers
Once you define enantiomers with examples, you will be able to understand the properties of these pairs of compounds too. Let us take a quick look into the properties of enantiomers.
They are physically and chemically identical compounds and exist in pairs.
They are either named dextrorotatory or levorotatory compounds based on the direction in which they bend a polarized light.
All the physical properties such as melting point, condensation point, boiling point, NMR spectra, and infrared absorptions are the same.
Even if the individual melting point of the compounds is similar, the melting point of their mixture might vary.
Only the chiroptical techniques can identify the difference between a pair of enantiomers. One such technique is the optical rotation of polarized lights.
These chiroptical properties depend on the bond angles, bond lengths, magnitude and sign of the torsional angles.
Why Prefer Using the Concept Page for Enantiomers Prepared By Vedantu?
Over the years, Vedantu has chosen the best chemistry mentors to teach students the basic and advanced concepts easily. These mentors know very well where a student can face difficulty. The new concepts of organic chemistry can be quite tough to understand when there is no proper guidance. Hence, the concept pages can act as the best reference material for students to clarify their doubts and prepare the chapters perfectly.
In this section, you will find the simplest definition and examples of enantiomers so that you can correlate them with the textbook chapter and figure out how to answer the questions in the exercise. This concept page can also act as a brilliant revision material when you have to finish a huge syllabus before an exam. You can refer to it online anytime anywhere to make your study schedule more flexible. Give it a try and find out how easy it is to understand what enantiomers with examples are.
FAQs on Examples of Enantiomers
1. What are enantiomers in Chemistry as per the CBSE syllabus?
Enantiomers are a type of stereoisomer. Specifically, they are pairs of molecules that are non-superimposable mirror images of each other, much like a person's left and right hands. To exist as enantiomers, a molecule must be chiral, meaning it lacks an internal plane of symmetry. They have the same chemical formula and connectivity but differ in the three-dimensional arrangement of their atoms.
2. What is a classic example of a pair of enantiomers?
A classic example of enantiomers is the molecule lactic acid. It has a central chiral carbon atom bonded to four different groups (-H, -OH, -COOH, and -CH₃). This asymmetry results in two distinct forms:
- (S)-(+)-Lactic acid: Found in sour milk and produced in muscles during exercise.
- (R)-(-)-Lactic acid: A byproduct of certain bacterial fermentation processes.
3. What are the key physical and chemical properties of a pair of enantiomers?
A pair of enantiomers share most of their physical and chemical properties. These identical properties include:
- Melting point
- Boiling point
- Density
- Solubility in achiral (non-chiral) solvents
- Reaction rates with achiral reagents
4. What structural feature must a molecule have to exhibit enantiomerism?
The most common structural feature required for a molecule to exhibit enantiomerism is the presence of a chiral centre. A chiral centre (or stereocentre) is typically a carbon atom that is bonded to four different atoms or groups. This tetrahedral arrangement with four unique substituents removes all planes of symmetry from the molecule, making it chiral and thus capable of having a non-superimposable mirror image.
5. How are enantiomers different from diastereomers?
Enantiomers and diastereomers are both types of stereoisomers, but they have a key difference.
- Enantiomers are stereoisomers that are non-superimposable mirror images of each other. They have identical physical properties except for the direction they rotate plane-polarised light.
- Diastereomers are stereoisomers that are not mirror images of each other. This occurs in molecules with two or more chiral centres. Unlike enantiomers, diastereomers have different physical properties, such as different melting points, boiling points, and solubilities.
6. Why are enantiomers described as non-superimposable mirror images?
Enantiomers are described as non-superimposable mirror images because of their inherent chirality or 'handedness'. An object is chiral if its mirror image cannot be perfectly aligned with the original, no matter how it is rotated. This is because the molecule lacks an internal plane of symmetry. Trying to superimpose one enantiomer on top of its mirror image will always result in a mismatch of some atoms, just as a left glove cannot be worn on a right hand.
7. What is a racemic mixture and why is it optically inactive?
A racemic mixture (or racemate) is a solution containing an equal amount (a 50:50 ratio) of a pair of enantiomers. This mixture is optically inactive because the optical effects of the two enantiomers cancel each other out. The dextrorotatory (+) enantiomer rotates plane-polarised light to the right by a certain degree, while the levorotatory (-) enantiomer rotates it to the left by the exact same degree. This perfect cancellation is known as external compensation, resulting in zero net optical rotation.
8. Where can we find examples of enantiomers in daily life or medicine?
Enantiomers are critically important in biology and medicine because our bodies are chiral environments. For example:
- Ibuprofen: This common painkiller is sold as a racemic mixture, but only the (S)-(+)-enantiomer is effective in reducing inflammation.
- Limonene: The (R)-enantiomer is responsible for the smell of oranges, while its mirror image, the (S)-enantiomer, smells of lemons.
- Thalidomide: A tragic example where one enantiomer was an effective sedative, but its mirror image caused severe birth defects. This highlights the vital importance of separating enantiomers in pharmaceuticals.
9. Why do biological systems, like the human body, often react differently to two enantiomers of the same drug?
Biological systems discriminate between enantiomers because enzymes and cellular receptors are themselves made of chiral molecules (like amino acids and sugars). These receptors have specific 3D shapes designed to bind with molecules of a corresponding shape. This is often explained by the 'hand-in-glove' analogy: a right-handed glove will only fit a right hand. Similarly, a specific drug receptor (the 'glove') will only bind effectively with one enantiomer of a drug (the 'correct hand'), leading to a desired therapeutic effect, while the other enantiomer may not fit or could cause unwanted side effects.
