Ketones vs. Aldehydes

[Belicia Tang 1B]

Hi, I am confused as to why ketones cannot occur at the end of a chain. Wouldn't the molecule C(CH3)2O (acetone) be an example of a ketone that occurs at the end of a chain (or rather, the ketone itself is the chain...)? Nothing else can bond to the two CH3's attached to the central C.

[Chem_Mod]

Hi Belicia,

Ketones and aldehydes are both carbonyls. Aldehydes exist at the end of the chain, where ketone exists in the middle, as you've mentioned.

Acetone is the simplest ketone, and the carbonyl does not exist at the end of the chain. Compare acetone to formaldehyde or acetalaldehyde to see what I mean.

For a carbonyl to be an aldehyde, there must be a hydrogen adjacent to the carbonyl, attached to the carbon.



Hope this helps.