But-2-ene on reaction with alkaline $\mathrm{KMnO}_{4}$ at elevated temperature followed by acidification will give :

(C) 2 molecules of $\mathrm{CH}_{3} \mathrm{COOH}$

(A) One molecule of $\mathrm{CH}_{3} \mathrm{CHO}$ and one molecule of $\mathrm{CH}_{3} \mathrm{COOH}$

(B) 2 molecules of $\mathrm{CH}_{3} \mathrm{CHO}$

JEE Main · 2019 · 12 Apr 2019 · Shift 1 · Hydrocarbons

But-2-ene on reaction with alkaline

KMnO_{4}

at elevated temperature followed by acidification will give :

(A)One molecule of $CH_{3} CHO$ and one molecule of $CH_{3} COOH$
(B)2 molecules of $CH_{3} CHO$
(C)2 molecules of $CH_{3} COOH$ ✓ Correct
(D)(see structure)

Answer: (C)

Solution

Hot alkaline

KMnO X_{4}

followed by acidification cleaves the double bond of but-2-ene oxidatively, and each doubly-bonded carbon, since it carries a hydrogen, is oxidised all the way to a carboxyl group rather than stopping at an aldehyde. The molecule

CH X_{3} CH = CHCH X_{3}

is symmetrical, so both halves are the same and the product is two molecules of acetic acid,

CH X_{3} COOH

JEE Main · 2019 · 12 Apr 2019 · Shift 1 · Single correct option

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