Phenyl Propyl Ketone is prepared from Butanoic acid as follow,
First Butanoic acid is treated with thionyl chloride so to change the -OH group into good leaving group (i.e. -Cl) and Butyryl chloride is generated.
Secondly, Chlorination of Benzene is done to synthesize chlorobenzene which on treatment with Mg metal in ether is converted into Phenyl Magnesium Chloride, which acts as a nucleophile and attacks the carbonyl carbon of Butyryl Chloride and upon hydrolysis gives Phenyl Propyl Ketone as shown below,