Question

Which of the following compounds is optically active?

• A. \(\text{C}_{2}\text{H}_{5}\text{-OH}\)
• B. \((\text{CH}_{3})_{2}\text{CH-CH}_{2}\text{-Cl}\)
• C. \(\text{CH}_{3}\text{-CH}(\text{Cl})\text{C}_{2}\text{H}_{5}\)
• D. \(\text{CCl}_{2}\text{F}_{2}\)

Hint:

An optically active compound has a chiral carbon bonded to four different groups.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept
A molecule is optically active if it contains a chiral carbon, one bonded to four different atoms or groups.

Step 2: Check each compound
\(\text{C}_{2}\text{H}_{5}\text{OH}\) has no carbon with four different groups.
\((\text{CH}_{3})_{2}\text{CHCH}_{2}\text{Cl}\) has a carbon with two identical methyl groups.
\(\text{CCl}_{2}\text{F}_{2}\) has repeated atoms.
\(\text{CH}_{3}\text{CH(Cl)C}_{2}\text{H}_{5}\) has a carbon bonded to \(\text{H}\), \(\text{Cl}\), \(\text{CH}_{3}\) and \(\text{C}_{2}\text{H}_{5}\).

Step 3: Compare the options
Only 2-chlorobutane, option (C), has a chiral centre.

Final Answer:
2-Chlorobutane is optically active. \[ \boxed{\text{(C) }\text{CH}_{3}\text{-CH}(\text{Cl})\text{C}_{2}\text{H}_{5}} \]