Relative reactivity of C-H towards chlorine radical is primary : secondary : tertiary = 1 : 3.8 : 5. The percentage of 2-chloro-2-methylbutane in the monochlorination product of 2-methylbutane (statistical and reactivity factors both included) is nearest to:

Answer: C

2-Methylbutane has 9 primary H (three

CH X_{3}

), 2 secondary H and 1 tertiary H. Weights:

9 \times 1 = 9

2 \times 3.8 = 7.6

1 \times 5 = 5

; total

21.6

. Tertiary fraction

= 5/21.6 = 23.1%

. The option with 51 percent ignores the number of H atoms of each type.