Question

Select the chain propagation steps in the free radical chlorination of methane :- (a) $C{l}_2⟶2\dot{Cl}$ (b) $\dot{C}l+C{H}_4⟶C{H}_{3}Cl+\dot{H}$ (c) $\dot{C}l+C{H}_4⟶{\dot{CH}}_3+HCl$ (d) $\dot{H}+C{l}_2⟶HCl+\dot{Cl}$ (e) $\dot{C}{H}_3+C{l}_2⟶C{H}_3-Cl+\dot{C}l$

• A. b, c, e
• B. a, c, e
• C. c, e
• D. b, c, d

Answer 1

Answer: (C)

(Free radical chlorination of methane)
$\Rightarrow$ FRSR
$C{H}_4+C{l}_2\stackrel{\mathrm{hv}}{\to }C{H}_3-Cl+HCl$
Mechanism :-
(i) Chain Initiation :-
$C{l}_2\stackrel{\mathrm{hv}}{\to }2\dot{Cl}$
(ii) Chain Propagation

(iii) Chain Termination
${\dot{CH}}_3+{\dot{CH}}_3\to C{H}_3-C{H}_3$
$\dot{Cl}+\dot{Cl}\to Cl-Cl$
${\dot{CH}}_3+\dot{Cl}\to C{H}_3-Cl$