1.Oxidation of Alcohols
Aldehydes:
Primary alcohols can be selectively oxidized to aldehydes using mild oxidizing agents such as pyridinium chlorochromate (PCC) or Dess-Martin periodinane.
Ketones:
Secondary alcohols are oxidized to ketones using stronger oxidizing agents like potassium permanganate (KMnO₄), potassium dichromate (K₂Cr₂O₇), or chromium trioxide (CrO₃).
2.Reduction of Carboxylic Acids and Esters
Aldehydes:
Carboxylic acids can be reduced to aldehydes using lithium aluminum hydride (LiAlH₄) followed by careful quenching, or diisobutylaluminum hydride (DIBAL-H).
Ketones:
Esters are reduced to ketones by using reagents like lithium aluminum hydride (LiAlH₄) or sodium borohydride (NaBH₄).
3.Ozonolysis of Alkenes
Both aldehydes and ketones can be synthesized by ozonolysis of alkenes.
The double bond is cleaved using ozone (O₃) followed by a reductive work-up with zinc (Zn) and acetic acid (CH₃COOH) or dimethyl sulfide (DMS).
4.Friedel-Crafts Acylation
Ketones:
Aromatic ketones are prepared via Friedel-Crafts acylation, where an aromatic ring reacts with an acyl halide in the presence of a Lewis acid catalyst like aluminum chloride (AlCl₃) or ferric chloride (FeCl₃).
5.Hydration of Alkynes
Aldehydes:
Terminal alkynes are converted to aldehydes through hydroboration-oxidation, using a borane reagent followed by oxidation with hydrogen peroxide (H₂O₂).
Ketones:
Internal alkynes are converted to ketones using a mercury(II) catalyst, such as mercuric sulfate (HgSO₄) in the presence of dilute sulfuric acid (H₂SO₄) and water.
6.Nucleophilic Substitution (Gattermann-Koch Reaction)
Aldehydes:
Aldehydes can be synthesized from haloalkanes via the Gattermann-Koch reaction, which involves the reaction with hydrogen cyanide (HCN) and a Lewis acid catalyst like anhydrous aluminum chloride (AlCl₃), followed by hydrolysis.
7.Grignard Reagents
Ketones:
Ketones can be produced by reacting Grignard reagents (RMgX) with nitriles, followed by hydrolysis of the resulting imine.