Preparation of aldehydes:

From acyl chloride (acid chloride):
Acyl chloride is hydrogenated over catalyst, palladium on barium sulphate. This reaction is called Rosenmund reduction.



From nitriles and esters:

Nitriles are reduced to corresponding  imine with stannous chloride in the presence of hydrochloric acid which on hydrolysis give corresponding aldehyde.



Preparation of ketones:

Treatment of acyl chlorides with dialkylcadmium gives ketone.



From benzene or substituted benzenes:

when benzene or substituted benzene is treated with acid chloride in the presece of anhydrous aluminium chloride, it afford the corresponding keton. This reaction is known as Friedel - crafts acylation reaction.