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Side chain oxidation of aryl alkanes takes place if there is at least one alpha hydrogen present by all accounts I presumed that there would be no reaction. However the answer given was trimethyl acetic acid. Is the answer key wrong?

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    $\begingroup$ chemistry.stackexchange.com/a/86/51553 $\endgroup$
    – Archer
    Jul 1 '18 at 18:01
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    $\begingroup$ Permanganate oxidises double bonds, even those in aromatic systems if you use forcing conditions. $\endgroup$
    – Waylander
    Jul 2 '18 at 6:17
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    $\begingroup$ My teacher has taught me same rxn. but acc. to him it happens only in acidic conditions not in basic medium $\endgroup$
    – Harsh jain
    Mar 10 '20 at 14:11
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A similar reaction with chromium oxide in alkaline solution has been documented.

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The acidic chromium oxide serves the same role as alkaline KMnO4 i.e a strong oxidizing agent. As pointed out by @Waylander in the comments permanganate oxidizes double bonds even in aromatic compounds.

Reference:
$\large{•}$ Chromium Oxidations in Organic Chemistry; By G. Cainelli, G. Cardillo

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For reaction with $\ce{KMnO4}$, the given compound must have a carbon atom attached directly to the ring and that carbon atom must have at least one hydrogen atom. But in case of tert-butylbenzene this condition isn't followed and hence is a special case. The final product obtained on reaction of tert-butylbenzene with $\ce{KMnO4}$ is Pivalic acid $\ce{(CH3)3CCOOH}$ (Common name: Dimethylpropanoic acid).

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Under normal circumstances, kmno4 will not oxidise tertiary butyl benzene. However, under drastic conditions, oxidative cleavage of bonds occur and a mixture of acetic acid and trimethyl acetic acid is formed. Hence the answer is incorrect. They should have mentioned the word 'drastic conditions'.

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    $\begingroup$ What are "drastic conditions?" If something lives in the hydrocarbon lakes of Titan then liquid water would seem drastic to it. $\endgroup$ Sep 6 '20 at 13:53

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