2,3-Dimethylbutane, $(CH X_{3}) X_{2} CH - CH (CH X_{3}) X_{2}$ , is monochlorinated with $Cl X_{2}$ and light. If the relative reactivity per hydrogen is primary : tertiary $= 1 : 5$ , the ratio of 1-chloro-2,3-dimethylbutane to 2-chloro-2,3-dimethylbutane in the product is

Answer: A

There are 12 primary H and 2 tertiary H. Weighted yields: primary

12 \times 1 = 12

, tertiary

2 \times 5 = 10

. The ratio is

12 : 10 = 6 : 5

. Statistical ratios alone (

12 : 2 = 6 : 1

) ignore the difference in reactivity.