chetoni

Chetoni, or ketones, are organic compounds containing the carbonyl group C=O bonded to two carbon substituents. The general structure is R-CO-R'. The carbonyl carbon is sp2-hybridized. Ketones are distinguished from aldehydes, which have at least one hydrogen attached to the carbonyl carbon.

Physical properties: The carbonyl group makes ketones polar; they often have higher boiling points than alkanes of similar size but do not form hydrogen bonds with themselves as alcohols do, so they are typically less volatile than alcohols of similar mass. Small ketones are miscible with water; larger ones are largely nonpolar and hydrophobic.

Nomenclature and examples: The simplest ketone is acetone, propan-2-one. Other examples include cyclohexanone, acetophenone (1-phenylethanone), and benzophenone. Ketone bodies like acetoacetate and beta-hydroxybutyrate are produced in liver during prolonged fasting or diabetes.

Reactivity: Ketones undergo nucleophilic addition at the carbonyl carbon. They can be reduced to secondary alcohols (e.g., with hydrogenation or hydride reagents) and formed by oxidation of secondary alcohols. Grignard reagents add to ketones to yield tertiary alcohols after workup. Enolate chemistry allows alpha-substitution and Michael-type additions. Ketones typically give negative Tollens’ and Fehling’s tests; 2,4-DNП test is positive for carbonyl compounds.

Applications: Ketones are widely used as solvents (acetone), intermediates in organic synthesis, and starting materials for pharmaceuticals and fragrances. They also play roles in metabolism as energy carriers in the form of ketone bodies.