Ketones

Ketones are a class of organic compounds characterized by a carbonyl group (C=O) bonded to two carbon atoms (R-CO-R'). The carbonyl carbon is electrophilic, making ketones reactive toward nucleophiles. The simplest ketone is acetone (propan-2-one).

Nomenclature follows the alkane-2-one pattern for IUPAC names, such as propan-2-one for acetone. Other common names reflect the two substituent groups, for example 2-butanone (ethyl methyl ketone) and acetophenone (1-phenylethanone).

Physical properties and uses: Ketones are typically colorless liquids or solids with a polar carbonyl group. They often have higher boiling points than alkanes of similar weight and many are miscible with water to varying degrees. Ketones are widely used as solvents in paints, coatings, plastics, and pharmaceuticals; acetone is one of the most common industrial solvents.

Reactions: The carbonyl carbon in ketones undergoes nucleophilic addition to form alcohols after reduction, and secondary alcohols can be oxidized to ketones. Methyl ketones can participate in the haloform reaction. Ketones also form acetals with diols and can participate in various condensation and enolate chemistry in organic synthesis.

Biological role: In metabolism, the liver produces ketone bodies—acetoacetate, beta-hydroxybutyrate, and acetone—during fasting or carbohydrate restriction, providing an energy source for tissues such as the brain. Elevated ketone levels can indicate ketoacidosis in diabetes or prolonged fasting.

Safety and occurrence: Ketones are generally flammable and may be eye and skin irritants. They occur naturally in small amounts and are synthesized widely for industrial and laboratory use.