Grade Upto college levelOrganic Chemistry

aldehydes generally undergo nucleophilic additions more readily than ketones.why?

2 Answers

Aldehydes are usually more reactive towards nucleophilic additions than ketones because of both steric and electronic effects.In aldehydes,the relatively small hydrogen atom is attached to one side of the carbonyl group ,while a larger R group is affixed to the other side.In ketones,however R groups are attached to both sides of the carbonyl group.Thus steric hinderance is less in aldehydes as compared to ketones.

Electronically aldehydes have only one R group to supply electrons towards the partially positive carbonyl carbon,while ketones have two electron supplying groups attached to the carbonl carbon.The greater amount of electrons being supplied to the carbonyl carbon,the less the partial positive charge on this atom and the weaker it becomes as a nucleus.

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Ruchi Shaw

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Mukesh Sharma

Approved Tutor Answer12 Years ago

aldehydes have at least one hydrogen bond in their structure,hence they do not cause much hindrances to attacking nucleophiles.ketones on the other hand have at least 2 methyl groups attached to their structure hence,the methyl group cause steric strains hence makes it difficult for the attacking nucleophile to bond with the carbonyl carbon.in this case aldehydes wiil be able to react with nuclephiles faster than ketones.
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Mukesh Sharma
askIITians Faculty