Hydrocarbons 2 Question 34
36. Which of the following will decolourise alkaline $\mathrm{KMnO}_{4}$ solution?
(1980, 1M)
(a) $\mathrm{C}{3} \mathrm{H}{8}$
(b) $\mathrm{CH}_{4}$
(c) $\mathrm{CCl}_{4}$
(d) $\mathrm{C}{2} \mathrm{H}{4}$
Objective Questions II
(One or more than one correct option)
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Answer:
Correct Answer: 36. (d)
Solution:
- Unsaturated compounds which contain $\mathrm{C}=\mathrm{C}$ or $\mathrm{C} \equiv \mathrm{C}$, decolourises the purple colour of alkaline $\mathrm{KMnO}_{4}$ solution.
$$ \mathrm{CH}{2}=\mathrm{CH}{2}+\underset{\substack{\text { purple } \ \text { coloured }}}{\mathrm{KMnO}{4}} \xrightarrow{\mathrm{HO}^{-}} \underset{\mathrm{CH}{2}-\mathrm{OH}}{\mathrm{CH}{2}-\mathrm{OH}}+\mathrm{MnO}{2} \downarrow $$
