• # question_answer 72)   The relative reactivity of $1{}^\circ ,\text{ }2{}^\circ ,\text{ }3{}^\circ$hydrogen's towards chlorination is 1: 3.8: 5. Calculate the percentages of all mono chlorinated products obtained from 2-methylbutane.

The given organic compound is : $\underset{2-\text{methylbutane}}{\mathop{C{{H}_{3}}-\overset{\overset{\text{C}{{\text{H}}_{\text{3}}}}{\mathop{|}}\,}{\mathop{CH}}\,-C{{H}_{2}}-C{{H}_{3}}}}\,$ This compound has 9 primary hydrogen; 2 secondary and one tertiary hydrogen atoms. The relative reactivity of $1{}^\circ ,\text{ }2{}^\circ$and $3{}^\circ$hydrogen atoms towards chlorination is 1: 3.8:5. Relative amount of product after chlorination = Number of hydrogen x relative reactivity $\begin{array}{*{35}{l}} Relative~~~{{1}^{o}}halide~~~\,\,\,{{2}^{o}}\text{ }halide~~~\,\,\,\,\,\,\,\,\,\,\,\,\,\,{{3}^{o}}halide \\ amount~~~9\times 1=9\text{ }\,\,\,\,\,\,\,\,2\text{ }\times 3.8=\,7.6\text{ }\,\,\,\,\,\,\,\,\,1\times 5=5 \\ \end{array}$ Total amount of mono chloro product $=9+7.6+5=21.6$ Percentage of $1{}^\circ$ mono =$\frac{9}{21.6}\times 100=41.7%$ chloro product Percentage of $2{}^\circ$ mono = $\frac{7.6}{21.6}\times 100=35.2%$ chloro product Percentage of $3{}^\circ$ mono $=\frac{5}{21.6}\times 100=23.1%$ chloro product