Question

Molecules whose mirror image is non-superimposable over them are known as chiral. Which of the following molecules is chiral in nature?

• A. 2-Bromobutane
• B. 1-Bromobutane
• C. 2-Bromopropane
• D. 2-Bromopropan-2-ol

Hint:

A carbon attached to four different groups is a chiral carbon. Molecules with one chiral carbon are usually optically active.

Answer 1

The Correct Option is A

Concept:
A molecule is chiral if it is not superimposable on its mirror image. The most common reason for chirality is the presence of a chiral carbon. A chiral carbon is a carbon atom attached to four different groups.

Step 1: Check 2-bromobutane.
Structure of 2-bromobutane is: \[ CH_3-CH(Br)-CH_2-CH_3 \] The second carbon is attached to four different groups: \[ CH_3 \] \[ C_2H_5 \] \[ Br \] \[ H \] Since all four groups are different, this carbon is chiral. Therefore, 2-bromobutane is chiral.

Step 2: Check 1-bromobutane.
Structure: \[ CH_3CH_2CH_2CH_2Br \] No carbon is attached to four different groups. So it is achiral.

Step 3: Check 2-bromopropane.
Structure: \[ CH_3-CH(Br)-CH_3 \] The central carbon is attached to two identical \(CH_3\) groups. So it is not chiral.

Step 4: Check 2-bromopropan-2-ol.
The central carbon has two identical methyl groups. So it is not chiral.

Step 5: Final answer.
Only 2-bromobutane has a carbon attached to four different groups. Hence, the correct answer is: \[ \boxed{(A)\ \text{2-Bromobutane}} \]