If ketone and an alkene are in the same compound and the compound is made to react with H 2 - Ni 1 equivalent then alkene will attack or carbonyl-

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If ketone and...

Question

If ketone and an alkene are in the same compound and the compound is made to react with H²/ Ni (1 equivalent ) then alkene will attack or carbonyl ?

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Solution

You are asking the preference of hydrogen on carbonyl group and alkene group
Consider the following compound
CH2=CH-CH2-CHO
If it is reacted with one mole H2 then the preference will be on alkene over carbonyl group.
This is because

All the reaction that is taking place on alkene is electrophilic addition reactions. That means a positive charged H+ has to attach the molecule to give the product. Generation of H+ is easier so the reaction will take place in alkene

But all the reaction taking place in carbonyl group (C=O) is nucleophilic addition reactions. So the reaction has to start through negative ions. Generating H- ion is. not possible. So this hydrogenation is difficult to carry comparing with alkene.

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