Question

Which of the following compound has chiral carbon atom?

• A. 2-chlorobutane
• B. 2, 2-dichlorobutane
• C. 1-chlorobutane
• D. 2-chloro 2-methylpropane

Hint:

To identify a chiral carbon quickly, check whether the carbon atom is bonded to four different groups. If yes, the compound can show optical isomerism.

Answer 1

The Correct Option is A

Step 1: Recall the condition for chirality.
A carbon atom is said to be chiral when it is attached to four different atoms or groups. Such a carbon is also called an asymmetric carbon atom. If any two attached groups are the same, then the carbon atom is not chiral. Step 2: Examine option (A) 2-chlorobutane.
The structure of 2-chlorobutane is:
\( \text{CH}_3-\text{CH}(\text{Cl})-\text{CH}_2\text{CH}_3 \)
The second carbon atom is attached to:

• \( \text{Cl} \)
• \( \text{H} \)
• \( \text{CH}_3 \)
• \( \text{CH}_2\text{CH}_3 \)

All four groups are different, so this carbon atom is chiral. Step 3: Check the remaining options.

• (B) 2,2-dichlorobutane: The second carbon has two identical chlorine atoms attached, so it cannot be chiral.
• (C) 1-chlorobutane: The carbon attached to chlorine does not have four different groups, so it is achiral.
• (D) 2-chloro 2-methylpropane: The central carbon is attached to three identical methyl groups, so it is not chiral.

Step 4: Conclusion.
Therefore, the compound that contains a chiral carbon atom is 2-chlorobutane.
Final Answer:2-chlorobutane.