Question

Which of the following will liberate a colourless gas when treated with sodium metal?

• A. CH₃-CH₂-O-CH₂-CH₃
• B. CH₃-CH₂-OH
• C. CH₃-CH₂-CH₂-CH₃
• D. Cyclohexanol

Answer 1

Answer: (B), (D)

B, D

Answer 2

Sodium metal reacts with compounds containing acidic hydrogen atoms to liberate hydrogen gas (H₂), which is a colorless gas.

• (A) Diethyl ether (CH₃-CH₂-O-CH₂-CH₃): Ethers do not have acidic hydrogens.
• (B) Ethanol (CH₃-CH₂-OH): Alcohols have an acidic hydrogen atom in the hydroxyl (-OH) group. This hydrogen can be displaced by sodium metal, producing hydrogen gas. $2\text{CH}_3\text{CH}_2\text{OH} + 2\text{Na} \rightarrow 2\text{CH}_3\text{CH}_2\text{ONa} + \text{H}_2\uparrow$
• (C) Butane (CH₃-CH₂-CH₂-CH₃): Alkanes do not have acidic hydrogens.
• (D) Cyclohexanol: Like other alcohols, cyclohexanol has an acidic hydrogen atom in the hydroxyl (-OH) group, which reacts with sodium metal to liberate hydrogen gas. $2\text{C}_6\text{H}_{11}\text{OH} + 2\text{Na} \rightarrow 2\text{C}_6\text{H}_{11}\text{ONa} + \text{H}_2\uparrow$

Both (B) and (D) will liberate a colorless gas (H₂) when treated with sodium metal.