Organic Deductive Question - Tips from Mr Khemistry
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19th August 2017

Organic Deductive Questions

Organic Chemistry

Deductive Questions – Side Reactions

When you have only one C=C in the organic molecule and question says that when the compound is heated with acidified manganate (VII), 3 fragments are obtained. This means that there was actually TWO cleavage of bonds.

But shouldn’t it be only two fragments since the oxidative cleavage only occurs at the C=C bond?

The clue lies in the often overlooked detail that whenever you have heat with acidified aqueous medium, you can also have acidic hydrolysis of esters/amides. So the initial molecule might have ester or amide functional groups on top of alkene functional group.

Same goes for iodoform test, where you use iodine with heat in a basic medium. Main reaction is the iodoform reaction, but basic hydrolysis can also occur.

Be sure to watch out for these “hidden” side reactions!

Clue: Solvent

Halogenoalkanes reacts with KOH in aqueous and alcoholic medium to form two different products.

This is one of the most common questions in organic chemistry, where different solvents will affect the type of reaction happening.

In this case, RX will undergo elimination of HX in alcoholic medium but undergo nucleophilic substitution in aqueous medium.

Another twist could be RX undergoing nucleophilic substitution reaction but giving two different products. This could arise when the solvent can also act as a nucleophile. eg ethanol can give ethoxide

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