ketone n : any of a class of organic compounds having a carbonyl group linked to a carbon atom in each of two hydrocarbon radicals

English

Etymology

From keton < Aketon < acétone. See acetone.

Noun

1. A homologous series of organic molecules whose functional group is an oxygen atom joined to a carbon atom—by a double bond—in a carbon-hydrogen based molecule.
   • acetone R1 = R2 = CH3
   • methyl ethyl ketone R1 = CH3, R2 = C2H5
   • camphor C₁₀H₁₇O

Derived terms

• ketoacidosis
• ketogenesis
• ketone body
• ketosis

Related terms

• aldehyde R2 = H
• tautomerism

Translations

References

A ketone (pronounced as key tone) is either the functional group characterized by a carbonyl group (O=C) linked to two other carbon atoms or a chemical compound that contains a carbonyl group. A ketone can be generally represented by the chemical formula:

R1(CO)R2.

A carbonyl carbon bonded to two carbon atoms distinguishes ketones from carboxylic acids, aldehydes, esters, amides, and other oxygen-containing compounds. The double-bond of the carbonyl group distinguishes ketones from alcohols and ethers. The simplest ketone is acetone (systematically named propan-2-one).

The carbon atom adjacent to a carbonyl group is called the α-carbon. Hydrogens attached to this carbon are called α-hydrogens. In the presence of an acid catalyst the ketone is subjected to so-called keto-enol tautomerism. The reaction with a strong base gives the corresponding enolate. A diketone is a compound containing two ketone groups.

Nomenclature

• • the reaction with ammonia or a primary amine gives an imine + water
  • the reaction with secondary amine gives an enamine + water
  • the reaction with a Grignard reagent gives a magnesium alkoxide and after aqueous workup a tertiary alcohol
  • the reaction with an organolithium reagent also gives a tertiary alcohol
  • the reaction with an alcohol, an acid or base gives a hemiketal + water and further reaction with an alcohol gives the ketal + water. This is a carbonyl-protecting reaction.
  • reaction of RCOR' with sodium amide results in cleavage with formation of the amide RCONH2 and the alkane R'H, a reaction called the Haller-Bauer reaction (1909)
• Electrophilic addition, reaction with an electrophile gives a resonance stabilized cation.
• the reaction with phosphonium ylides in the Wittig reaction gives alkenes
• reaction with water gives geminal diols
• reaction with thiols gives a thioacetal
• reaction with hydrazine or derivatives of hydrazine gives hydrazones
• reaction with a metal hydride gives a metal alkoxide salt and then with water an alcohol
• reaction of an enol with halogens to form α-haloketone
• a reaction at an α-carbon is the reaction of a ketone with heavy water to give a deuterated ketone-d.
• fragmentation in photochemical Norrish reaction
• reaction with halogens and base of methyl ketones in the Haloform reaction
• reaction of 1,4-aminodiketones to oxazoles by dehydration in the Robinson-Gabriel synthesis
• reaction of aryl alkyl ketones with sulfur and an amine to amides in the Willgerodt reaction

Biochemistry

Acetone, acetoacetate and beta-hydroxybutyrate are ketones (or ketone bodies) generated from carbohydrates, fatty acids and amino acids in humans and most vertebrates. Ketones are elevated in blood after fasting including a night of sleep, and in both blood and urine in starvation, hypoglycemia due to causes other than hyperinsulinism, various inborn errors of metabolism, and ketoacidosis (usually due to diabetes mellitus). Although ketoacidosis is characteristic of decompensated or untreated type 1 diabetes, ketosis or even ketoacidosis can occur in type 2 diabetes in some circumstances as well. Acetoacetate and beta-hydroxybutyrate are an important fuel for many tissues, especially during fasting and starvation. The brain, in particular, relies heavily on ketone bodies as a substrate for lipid synthesis and for energy during times of reduced food intake. At the NIH, Dr. Richard Veech refers to ketones as "magic" in their ability to increase metabolic efficiency, while decreasing production of free radicals, the damaging byproducts of normal metabolism. His work has shown that ketone bodies may treat neurological diseases such as Alzheimer's and Parkinson's disease, and the heart and brain operate 25% more efficiently using ketones as a source of energy.

Applications

Ketones are often used in perfumes and paints to stabilize the other ingredients so that they don't degrade as quickly over time. Other uses are as solvents and intermediates in chemical industry. Examples of ketones are acetone, acetophenone, and methyl ethyl ketone.

See also

• List of publications in organic chemistry
• Ketosis
• Ketone bodies (Medical term referring to all or either of the three ketones occurring in the body).

References