Question

Hydrocarbon (A) reacts with bromine by substitution to form an alkyl bromide which by Wurtz reaction is converted to gaseous hydrocarbon containing less than four carbon atoms. (A) is

• A. CH ≡ CH
• B. CH₃ - CH₃
• C. CH₂ = CH₂
• D. CH₄

Answer 1

The Correct Option is D

To solve this question, we need to identify hydrocarbon (A) based on the given conditions: it reacts with bromine in a substitution reaction to form an alkyl bromide, which can then participate in a Wurtz reaction to produce a gaseous hydrocarbon with fewer than four carbon atoms.

Let's analyze each option:

1. CH ≡ CH: Acetylene can react with bromine, but the reaction involves addition rather than substitution. The product would not be an alkyl bromide. Thus, this cannot be the correct option.
2. CH₃ - CH₃: Ethane undergoes substitution with bromine to form ethyl bromide (C₂H₅Br). During the Wurtz reaction, two ethyl bromide molecules would couple to form butane (C₄H₁₀). Since the product is not a gaseous hydrocarbon with fewer than four carbons, this option is incorrect.
3. CH₂ = CH₂: Ethylene would react with bromine via addition, not substitution, again leading to incorrect products not suitable for the Wurtz reaction.
4. CH₄: Methane undergoes substitution with bromine to form methyl bromide (CH₃Br). In the Wurtz reaction, two methyl bromide molecules couple to form ethane (C₂H₆), which is a gaseous hydrocarbon with less than four carbon atoms.

By process of elimination and understanding of reaction mechanisms, the correct answer is indeed CH₄, as it satisfies the condition given in the question.