Ketoonid

Ketones, or ketoonid, are a class of organic compounds characterized by a carbonyl group (C=O) bonded to two carbon atoms (R-CO-R'). They are distinct from aldehydes, which have at least one hydrogen on the carbonyl carbon. Ketones can feature alkyl, aryl, or mixed substituents, and their carbonyl carbon is typically sp2-hybridized, giving the group planar geometry.

Naming and structure: Simple ketones are named by identifying the longer carbon chain and adding the suffix -one, with a locant if needed (for example, propanone is acetone). Common names often reference the substituents on either side of the carbonyl (e.g., acetone, methyl ethyl ketone, or benzophenone).

Physical properties: Ketones are polar due to the carbonyl group, which results in relatively high boiling points compared with nonpolar hydrocarbons of similar size. Small ketones are miscible with water, while larger ones are miscible only to a limited extent. They are typically liquids at room temperature and can be flammable, with odors ranging from sharp to fruity in some cases.

Preparation and reactions: Ketones are commonly prepared by oxidation of secondary alcohols (R-CHOH-R' → R-CO-R') or by other oxidation methods of suitable precursors. In chemical reactions, the carbonyl carbon of ketones undergoes nucleophilic addition (e.g., Grignard reagents or hydride reductions to form secondary alcohols). Ketones also participate in enolate chemistry and can be used in various condensation and acyl-transfer reactions.

Occurrence and uses: Ketones are widely used as solvents (for example, acetone), in pharmaceuticals, and as intermediates in organic synthesis. In biology, ketone bodies (e.g., acetoacetate, beta-hydroxybutyrate, and acetone) are produced during fatty acid metabolism and can serve as alternative energy sources during fasting or diabetes.

Safety: Many ketones are flammable and can be irritants or hazards if inhaled or ingested. Proper ventilation and handling procedures are recommended.