JEE Main 2022 · 26 July · morning · Single correct · +4 / −1

Cl(•)+CH₄ → A+B
A and B in the above atmospheric reaction step are :

  1. (a) C₂ H₆ and Cl₂
  2. (b) C(•) HCl₂ and H₂
  3. (c) C(•)H₃ and HCl
  4. (d) C₂ H₆ and HCl
Answer and solution

Answer (c) C(•)H₃ and HCl

Solution

Chemistry ma’am · 3 steps

A chlorine radical grabs one hydrogen from methane and leaves a methyl radical behind.

  1. Chain propagation. This is the first propagation step of free radical chlorination. The Cl radical has one unpaired electron and wants one more to complete its octet.
  2. Hydrogen abstraction. It takes a hydrogen atom, with that atom's one electron, from CH₄. The C-H bond breaks evenly (homolysis), so carbon keeps the other electron and becomes a radical.

    Cl(•) + CH₄ → C(•)H₃ + HCl

  3. So. A is the methyl radical C(•)H₃ and B is HCl, which is option (c). One radical goes in and one radical comes out, so the chain keeps going.

The idea to keep. In a propagation step, one radical goes in and one new radical comes out. Halogen radicals abstract H from alkanes to give HX and an alkyl radical.

Answer from the NTA final answer key. Solution by PrepWiser.

Study Hydrocarbons — Alkanes

Asked about 40 times in JEE Main since 2020. This question is from 2022.