Alcohols and Ethers - Result Question 6
####9. Which is the most suitable reagent for the following transformation?
(2019 Main, 10 Jan II)
$CH _3-CH=CH-CH _2 CO _2 H$
(a) Tollen’s reagent
(b) $I _2 / NaOH$
(c) Alkaline $KMnO _4$
(d) $CrO _2 Cl _2 / CS _2$
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Answer:
Correct Answer: 9. (a)
Solution:
- The most suitable reagent to carry out given transformation is $I _2 / NaOH$
$\underset{6}{CH _3} \underset{5}{C} H=\underset{4}{C} H-C _3 H _2-\underset{2}{C} OH-\underset{1}{C} H _3 \xrightarrow[\text { (Oxidative cleavage) }]{\text { Strong oxidation, }[O]}$
$$ \underset{6}{CH _3}-\underset{5}{C} H=\underset{4}{C} H-\underset{3}{CH _2}-\underset{2}{C}-OH $$
Here, the haloform reaction will give following reaction:
(i) Tollen’s reagent $\left(AgNO _3+NH _4 OH\right)$ is a mild oxidising agent. It does not react with $-CH-CH _3$ group
$\left(2^{\circ}\right.$-alcohol).
(ii) Alkaline $KMnO _4$ cannot perform the oxidative cleavage, rather it will hydroxylate the $C=C$.
(iv) $CrO _2 Cl _2 / CS _2$ will not react here.
