Ketone



  A ketone (pronounced as key tone) is either the chemical compound that contains this functional group. A ketone can be generally represented by the formula:

R1(O)R2.

A carbonyl carbon bonded to two carbon atoms distinguishes ketones from ethers. The simplest ketone is acetone (systematically named 2-propanone[1]).

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 diketone is a compound containing two ketone groups.

Nomenclature

 In general, ketones are named using benzophenone predominate, and these are considered retained IUPAC names [2], although some introductory chemistry texts use names such as propanone.

Oxo is the formal IUPAC nomenclature for a ketone functional group. Oxo also refers to a single oxygen atom coordinated to a transition metal (a metal oxo).

Physical properties

A carbonyl group is molecular weight.

Acidity

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.

Spectroscopic properties

infrared spectroscopy, at around 1700 cm−1 (slightly higher or lower, depending on the chemical environment)

Synthesis

Several methods exist for the preparation of ketones in the laboratory:

  • Ketones can be created by acetone:
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 are also prepared by Gem halide hydrolysis.
  • Alkynes can be turned into enols through hydration in the presence of an acid and HgS04, and subsequent enol-keto tautomerization gives a ketone. This always produces a ketone, even with a terminal alkyne, and Sia2BH is needed to get an aldehyde from an alkyne
  • Aromatic ketones can be prepared in the Fries rearrangement.
  • In the Kornblum–DeLaMare rearrangement ketones are prepared from peroxides and base
  • In the Ruzicka cyclization, cyclic ketones are prepared from dicarboxylic acids.
  • In the Nef reaction, ketones form by hydrolysis of salts of secondary nitro compounds

Reactions

Ketones engage in many organic reactions:

  • nucleophile gives a tetrahedral carbonyl addition compound.
    • the reaction with the anion of a terminal alkyne gives a hydroxyalkyne
    • the reaction with 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 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) [3]
  • electrophile gives a resonance stabilized cation.
  • the reaction with phosphonium ylides in the alkenes
  • reaction with water gives geminal diols
  • reaction with thioacetal
  • reaction with hydrazones
  • reaction with a metal hydride gives a metal alkoxide salt and then with water an alcohol
  • reaction of an 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

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,[4] and the heart and brain operate 25% more efficiently using ketones as a source of energy.[5]

Applications

Ketones are often used in perfumes and methyl ethyl ketone.

See also

References

  1. ^ The position of the carbonyl group is usually denoted by a number; in propanone there can only be one position. While propanone or 2-propanone is how the molecule should be named according to systematic nomenclature, the name "acetone" is retained in official IUPAC nomenclature
  2. ^ List of retained IUPAC names retained IUPAC names Link
  3. ^ http://nagoyaren.homeip.net/chem/reactions/123.htm
  4. ^ Y. Kashiwaya, T. Takeshima, N. Mori, K. Nakashima, K. Clarke and R. L. Veech (2000). "D-beta -Hydroxybutyrate protects neurons in models of Alzheimer's and Parkinson's disease". PNAS 97 (10): 5440-5444. doi:10.1073/pnas.97.10.5440.
  5. ^ Y. Kashiwaya, K. Sato, N. Tsuchiya, S. Thomas, D. A. Fell, R. L. Veech and J. V. Passonneau (1994). "Control of glucose utilization in working perfused rat heart". J. Biol. Chem. 269 (41): 25502-25514.
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