Question

Assertion :Statement-I : free radical chlorination of $n$-butane gives $72\%$ of $2$-chlorobutane and $28\%$ of $1$-chlorobutane though it has six primary and four secondary hydrogens.
Because Reason: Statement-II : A secondary hydrogen is abstracted more easily than the primary hydrogen.

• A. (A)Statement-I is true, Statement-II is true ; Statement-II is correct explanation for Statement-I.
• B. (B)Statement-I is true, Statement-II is true ; Statement-II is NOT a correct explanation for Statement-I.
• C. (C)Statement-I is true, Statement-II is false.
• D. (D)Statement-I is false, Statement-II is true.

Answer 1

The correct option is A (A)Statement-I is true, Statement-II is true ; Statement-II is correct explanation for Statement-I.

Free radical chlorination of n-butane gives $72$% of $2$-chlorobutane and $28$% of $1$-chlorobutane though it has six primary and four secondary hydrogens. This is because a secondary hydrogen is abstracted more easily than the primary hydrogen.

Hence, Statement-I is true, Statement-II is true ; Statement-II is correct explanation for Statement-I.

$\frac{\text{Percent of 1-chlorobutane}}{\text{Percent of 2-chlorobutane}}=\frac{\text{Number of primary H}}{\text{Number of secondary H}}\times \frac{\text{Reactivity of primary H}}{\text{Reactivity of secondary H}}=\frac{6}{4}\times \frac{1.0}{3.8}=\frac{6}{15.2}=\frac{28}{72}$