Question

Consider two alternative mechanisms for the chlorination of methane, Which step is crucial in deciding which mechanism is not likely to be observed?
Mechanism I:

$A.C{l}_2\to 2C{l}^{\ast }$
$B.C{l}^{\ast }+C{H}_4\to HCl{+}^{\ast }C{H}_3$
$C.\dot{C}{H}_3+C{l}_2\to C{H}_{3}Cl+C{l}^{\ast }$
Mechanism II:

$D.C{l}_2\to 2C{l}^{\ast }$
$E.C{l}^{\ast }+C{H}_4\to C{H}_{3}Cl+H^{\ast }$
$F.H^{\ast }+C{l}_2\to HCl+C{l}^{\ast }$

• A. $I$
• B. $II$
• C. $I$ and $II$ both
• D. None

Answer 1

The correct option is B $II$

In chlorination of methane in presence of sunlight is the free radical mechanism where chain elongation step is rate determining step. For that formation of $C{l}^{\ast }$ free radical is crucial.

Chain elongation process-

$C{l}_2+C{H}_3^{\ast }\to C{H}_{3}Cl+C{l}^{\ast }$