Question

Racemic mixture is formed by mixing two (a) Isomeric compounds (b) Chiral compounds (c) Meso compounds (d) Enantiomers with chiral carbon

Short answer

Racemic mixture is formed by mixing (d) Enantiomers with chiral carbon.

Step-by-step solution

Understand Racemic Mixture

A racemic mixture is a mixture that contains equal amounts of two enantiomers. Enantiomers are chiral molecules that are non-superimposable mirror images of each other. They have the same chemical composition and structure but differ in spatial arrangement, resulting in different optical activities.

Examine the Given Options

We have the following options: (a) Isomeric compounds, (b) Chiral compounds, (c) Meso compounds, (d) Enantiomers with chiral carbon. We need to determine which of these refers to the components of a racemic mixture.

Evaluate Each Option

- Option (a): Isomeric compounds can include enantiomers, geometric isomers, or structural isomers. Only enantiomers can form racemic mixtures. - Option (b): Chiral compounds have chirality but not all chiral systems form racemic mixtures. - Option (c): Meso compounds are achiral despite having chiral centers and cannot form racemic mixtures. - Option (d): Enantiomers with chiral carbon are mirror-image isomers, specifically related to racemic mixtures.

Make a Decision

The correct description of a racemic mixture pertains to (d) Enantiomers with chiral carbon. A racemic mixture consists of equal parts of enantiomers, which are indeed chiral molecules with one or more chiral carbons.

Key concepts

Chirality

Chirality is a fundamental concept in chemistry and biology. It refers to the geometric property of a molecule that is not superimposable on its mirror image.
Imagine your hands; they are mirror images of each other but cannot be perfectly aligned, no matter how you rotate one hand. This is a classic example of chirality. In chemistry, this property is common in molecules with an asymmetric carbon atom, with four different groups attached. The presence of this asymmetric carbon, often called the chiral center, allows for the existence of two distinct configurations, which are non-superimposable mirror images of each other.
These two configurations are called enantiomers, having distinct spatial arrangements. Understanding chirality is crucial, as it can affect the physical and chemical properties of the molecules, influencing their interactions with other chiral substances.

Enantiomers

Enantiomers are pairs of molecules that are mirror images but cannot be overlaid on each other, much like left and right hands. These molecules always contain one or more chiral centers, which give rise to this unique non-superimposable quality.
Both molecules in a pair have the same chemical structure and formula but differ in their three-dimensional spatial arrangement. Key characteristics of enantiomers:

• They generally exhibit identical physical properties, such as melting point and boiling point.
• They react in the same way with achiral reagents but may show strikingly different behaviors with chiral reagents.
• The most notable difference between enantiomers is their effect on polarized light, known as optical activity.

Understanding enantiomers is vital in fields like pharmaceuticals, as only one enantiomer in a pair may be biologically active or safe.

Optical Activity

Optical activity is a fascinating phenomenon exhibited by chiral substances, including enantiomers. When plane-polarized light passes through a solution of chiral molecules, such as enantiomers, it rotates the light's plane of polarization.
This rotation occurs due to the interaction of light with the chiral centers in the molecules, and the degree of rotation can be measured and is known as the optical rotation angle. Important facts about optical activity:

• Enantiomers will rotate light to the same degree but in opposite directions. One will be termed the dextrorotatory ( + ) and the other levorotatory ( − ) enantiomer.
• A racemic mixture, containing equal amounts of enantiomers, shows no optical activity because the rotations cancel each other out.
• The measurement of optical activity is crucial for identifying and distinguishing enantiomers in research and industrial applications.

Optical activity helps chemists and biochemists understand the behavior of chiral substances and their interactions in a more comprehensive manner.