Aldehydes, Ketones and Carboxylic Acids - Preparation of Aldehydes and Ketones

Oxidation of Alcohols: Primary alcohols ($1^\circ$) are oxidized to aldehydes using mild oxidizing agents like Pyridinium chlorochromate ($PCC$). Secondary alcohols ($2^\circ$) are oxidized to ketones using $CrO_3$.

Dehydrogenation of Alcohols: Passing vapors of alcohols over heated copper at $573\,K$. $1^\circ$ alcohols give aldehydes, while $2^\circ$ alcohols give ketones.

Ozonolysis of Alkenes: Alkenes react with $O_3$ followed by $Zn/H_2O$ to yield aldehydes or ketones depending on the substitution pattern of the alkene.

Hydration of Alkynes: Addition of water to ethyne in the presence of $H_2SO_4$ and $HgSO_4$ gives acetaldehyde. Other alkynes yield ketones.

Rosenmund Reduction: Acyl chlorides are hydrogenated over catalyst, palladium on barium sulphate ($Pd/BaSO_4$), partially poisoned by sulfur or quinoline to yield aldehydes.

Stephen Reaction: Nitriles are reduced to corresponding imines with stannous chloride ($SnCl_2$) in the presence of hydrochloric acid ($HCl$), which on hydrolysis give corresponding aldehydes.

Etard Reaction: Chromyl chloride ($CrO_2Cl_2$) oxidizes the methyl group of toluene to a chromium complex, which on hydrolysis gives benzaldehyde.

Gatterman-Koch Reaction: Benzene or its derivative is treated with carbon monoxide ($CO$) and hydrogen chloride ($HCl$) in the presence of anhydrous $AlCl_3$ or $CuCl$ to give benzaldehyde.

Preparation of Ketones from Nitriles: Treating a nitrile with a Grignard reagent followed by hydrolysis yields a ketone.

Friedel-Crafts Acylation: Benzene reacts with acid chlorides in the presence of anhydrous $AlCl_3$ to produce aromatic ketones.