Hydrocarbons 2 Question 13
13. The synthesis of 3-octyne is achieved by adding a bromoalkane into a mixture of sodium amide and an alkyne. The bromoalkane and alkyne respectively are
(2010)
(a) $\mathrm{BrCH}{2} \mathrm{CH}{2} \mathrm{CH}{2} \mathrm{CH}{2} \mathrm{CH}{3}$ and $\mathrm{CH}{3} \mathrm{CH}_{2} \mathrm{C} \equiv \mathrm{CH}$
(b) $\mathrm{BrCH}{2} \mathrm{CH}{2} \mathrm{CH}{3}$ and $\mathrm{CH}{3} \mathrm{CH}{2} \mathrm{CH}{2} \mathrm{C} \equiv \mathrm{CH}$
(c) $\mathrm{BrCH}{2} \mathrm{CH}{2} \mathrm{CH}{2} \mathrm{CH}{2} \mathrm{CH}{3}$ and $\mathrm{CH}{3} \mathrm{C} \equiv \mathrm{CH}$
(d) $\mathrm{BrCH}{2} \mathrm{CH}{2} \mathrm{CH}{2} \mathrm{CH}{3}$ and $\mathrm{CH}{3} \mathrm{CH}{2} \mathrm{C} \equiv \mathrm{CH}$
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Answer:
Correct Answer: 13. (a)
Solution:
- $\mathrm{CH}{3} \mathrm{CH}{2} \mathrm{C} \equiv \mathrm{CH}+\mathrm{Br}-\mathrm{CH}{2} \mathrm{CH}{2} \mathrm{CH}{2} \mathrm{CH}{3}$
$$ \underset{-\mathrm{HBr}}{\longrightarrow} \mathrm{CH}{3} \mathrm{CH}{2}-\mathrm{C} \equiv \underset{\text { 3-octyne }}{\mathrm{C}}-\mathrm{CH}{2} \mathrm{CH}{2} \mathrm{CH}{2} \mathrm{CH}{3} $$
