(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
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, CH3-CO-CH3 (systematically named propanone).
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.
In general, ketones are named using IUPAC nomenclature
by changing the suffix -e
of the parent alkane
. For common ketones, some traditional names such as acetone
predominate, and these are considered retained IUPAC names , although some introductory chemistry texts use names such as propanone.
Oxo is the formal IUPAC nomenclature for a ketone functional group. However, other prefixes are also used by various books and journals. For some common chemicals (mainly in biochemistry), keto or oxo is the term used to describe the ketone (also known as alkanone) functional group. Oxo also refers to a single oxygen atom coordinated to a transition metal (a metal oxo).
A carbonyl group is polar
. This makes ketones polar compounds
. The carbonyl groups interact with water by hydrogen bonding
, and ketones are soluble in water. It is a hydrogen-bond acceptor, but not a hydrogen-bond donor, and cannot hydrogen-bond to itself. This makes ketones more volatile than alcohols
and carboxylic acids
of similar molecular weight
The α-hydrogen of a ketone is far more acidic (pKa
≈ 20) than the hydrogen of a regular alkane (pKa ≈ 50). This is due to resonance stabilization of the enolate ion
that is formed through dissociation. The relative acidity of the α-hydrogen is important in the enolization reactions of ketones and other carbonyl compounds.
is an important means for identifying ketones. Ketones and aldehydes will display a significant peak in infrared spectroscopy
, at around 1700 cm−1
(slightly higher or lower, depending on the chemical environment)
Several methods exist for the preparation of ketones in the laboratory:
- H3C-CH(OH)-CH3 → H3C-CO-CH3
- Two atoms of hydrogen are removed, leaving a single oxygen atom double-bonded to a carbon atom.
Ketones engage in many organic reactions
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
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. Research has also shown ketones play a role in reducing epileptic seizures with the so-called high-fat, near-zero carbohydrate Ketogenic Diet.
Ketones are mainly caused by high blood sugars.
Ketones are often used in perfumes
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
, and methyl ethyl ketone
A new fuel source?
Scientists are currently working on a new fuel source for the human body, ketone bodies. These chemicals are present in our bodies already, made by the liver from fat when glucose is in short supply. But until now they have not been considered a food. When properly prepared, it is chewed and provides energy for athletes as well as fuel for brain function.