Question

An organic compound will show optical isomerism is (1) Four groups attached to C-atom are different. (2) Threc groups attached to $\mathrm{C}$ -atom are different. (3) Two groups attached to C-atom are different. (4) Nll the groups attached to $\mathrm{C}$ -atom are same.

Short answer

Option 1 is correct: Four groups attached to a C-atom are different.

Step-by-step solution

- Understand Optical Isomerism

Optical isomerism occurs when a carbon atom is attached to four different groups. This carbon is known as a chiral or asymmetric carbon atom.

- Analyze Option 1

Check if having four different groups attached to a carbon atom fits the criteria for optical isomerism. Since a chiral center is required for optical isomerism, four different groups satisfy this condition.

- Analyze Option 2

Check if having three different groups attached to the carbon atom fits the criteria. This would not create a chiral center, as one group must be duplicated.

- Analyze Option 3

Check if having two different groups attached to the carbon atom fits the criteria. This would not create a chiral center, as two groups must be duplicated.

- Analyze Option 4

Check if having all groups attached to the carbon being the same fits the criteria. This clearly does not create a chiral center, as there is no variation in the groups.

- Choose the Correct Option

Based on the analysis, the presence of four different groups attached to a carbon atom is required for optical isomerism. Therefore, option 1 is correct.

Key concepts

chiral carbon

In the realm of organic chemistry, a chiral carbon is a carbon atom that has four different groups attached to it. This uniqueness allows the carbon to form non-superimposable mirror images, known as enantiomers. These mirror image molecules cannot be aligned perfectly when placed on top of each other, much like how your left and right hands are mirror images but not identical.
Recognizing a chiral carbon in molecular structures is crucial for determining whether a compound can exhibit optical isomerism. Remember:

• A carbon atom must have four different groups attached to be chiral.
• If any two groups are the same, it is not a chiral carbon.

To visualize this, consider the molecule lactic acid. The central carbon in lactic acid has four different groups: a hydrogen atom, a hydroxyl group (OH), a methyl group (CH₃), and a carboxyl group (COOH). This makes the central carbon atom chiral and enables lactic acid to exist in two enantiomeric forms.

asymmetric carbon atom

An asymmetric carbon atom is another term used interchangeably with a chiral carbon. It specifically refers to a carbon atom that is bonded to four distinct groups. This lack of symmetry is key to the carbon's chirality.
The importance of an asymmetric carbon becomes evident in the study of optical activity. This is because molecules with asymmetric carbon atoms can rotate plane-polarized light, a property used to distinguish between different enantiomers in the lab. Here’s what to keep in mind about asymmetric carbons:

• They are central to the concept of chirality.
• Their unique arrangement leads to molecules having 'handedness' (left-handed or right-handed forms).

For instance, the compound 2-butene does not display optical isomerism because its double bond does not allow for four different groups around a central carbon. In contrast, 2-butanol has an asymmetric carbon atom, making it possible for it to exhibit optical isomerism.

organic chemistry

Organic chemistry is the branch of chemistry dedicated to the study of carbon-containing compounds. This field encompasses a vast number of substances, including those found in living organisms and many synthetic materials. The study of optical isomerism falls within organic chemistry and is important for understanding the behavior and properties of different molecules.
Here are a few key points defining organic chemistry:

• It explores the structures, properties, and reactions of organic compounds.
• Carbon’s ability to form strong covalent bonds with many elements creates a diversity of stable compounds.

Understanding organic chemistry concepts like chiral and asymmetric carbons helps in grasping complex biochemical processes and in the development of pharmaceuticals. For instance, many drugs must be synthesized in their correct enantiomeric forms as often, only one form is therapeutically active or safe. Thus, the principles of organic chemistry are vital for several practical applications, from drug manufacturing to the creation of new materials.