Take the relative reactivities per hydrogen for Cl2 at 25 degC as primary : secondary : tertiary = 1 : 3.8 : 5. The alkane shown is monochlorinated at 25 degC. Treating each constitutionally different position separately, what percentage of the product is the tertiary chloride (nearest whole number)?

JEE Advanced levelSingle correct optionDifficulty 3 of 3o2258

Take the relative reactivities per hydrogen for $Cl X_{2}$ at 25 $^{\circ}$ C as primary : secondary : tertiary = 1 : 3.8 : 5. The alkane shown is monochlorinated at 25 $^{\circ}$ C. Treating each constitutionally different position separately, what percentage of the product is the tertiary chloride (nearest whole number)?

The alkane is methylcyclohexane. Weights: methyl H

3 \times 1 = 3

; ring CH

1 \times 5 = 5

; C-2/C-6

4 \times 3.8 = 15.2

; C-3/C-5

4 \times 3.8 = 15.2

; C-4

2 \times 3.8 = 7.6

; total 46. The tertiary 1-chloro-1-methylcyclohexane is

5/46 = 10.9%

, about 11%.