Question

Why are aldehydes more reactive than ketones?

Answer 1

Consider the shrubbery around the carbonyl group in an aldehyde, versus that around a ketone group.

Explanation:

Should we compare `RC(=O)H` to `RC(=O)R`, clearly the aldehyde is less sterically encumbered. Even for acetone versus acetaldehyde, the ipso carbon is encumbered by 2 methyl groups in the ketone, versus 1 methyl in the aldehyde.

So in terms of sterics, the aldehyde should be a much more reactive proposition.

In terms of electronics, the aldehyde may be oxidized up a further step to give the carboxylic acid. Such oxidation is not available to a ketone, unless we break the `C-C` chain.