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JEE Advanced levelSingle correct optionDifficulty 3 of 3o2092

2-Methylbutane reacts with $Br X_{2}$ and light. Relative reactivity per hydrogen is primary : secondary : tertiary $= 1 : 82 : 1600$ . The percentage of 2-bromo-2-methylbutane in the monobromo mixture is closest to

A9.2%
B0.5%
C90.2%
D95.1%

Answer: C

2-Methylbutane has 9 primary, 2 secondary and 1 tertiary H. Weights:

9

,

2 \times 82 = 164

,

1 \times 1600 = 1600

; total

= 1773

. Tertiary product

= 1600/1773 \times 100 = 90.2%

. Omitting the number of hydrogens gives

95.1%

, which is wrong.

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