Question

In the reaction, $C{l}_2+C{H}_4\stackrel{hv}{\to }C{H}_{3}Cl+HCl$ presence of a small amount of oxygen

• A. increases the rate of reaction for a brief period of time
• B. decreases the rate of reaction for a brief period of time
• C. does not affect the rate of reaction
• D. completely stops the reaction

Answer 1

Answer: (B)

During chlorination of methane, a small amount of oxygen acts as radical inhibitor. $O_2$ combines with ${}^{\ast }C{H}_3$ free radical to form methyl peroxy free radicals which are much less reactive than $C{H}_3$ free radicals and hence the reaction slows down. After the inhibitor has been consumed, the reaction proceeds normally. $\underset{\begin{array}{c}methyl\\ radical\end{array}}{{}^{\ast }C{H}_3+O-O}\to \underset{\begin{array}{c}methyl\\ peroxyradical\end{array}}{C{H}_3-O-O^{\bullet }}$