Diketone is a molecule which
contains two ketone carbonyl groups. Diacetyl (CH3COCOCH3), 2,3-butadione, is
the simplest aliphatic diketone. It is an alpha-diketone which has two ketone
groups side-by-side. Usually, alpha-diketone imparts a carmel like or buttery
flavor. Diketone compounds take a role in creating various fragrances. Benzil
is an aromatic diketone, the fundamental structure
of photo sensitive molecule which is broken down into free
radicals upon exposure to ultraviolet radiation.
Acetoacetone is a
beta-diketone (1,3-diketone) which two ketones are separated only by one carbon. The
beta-ketone is stable as a conjugated enol rather than alpha-diketone due to the
delocalization which makes the counterion more stable and less likely to regain
the proton. Ascorbic acid is an example of enol compound. Enol compounds form
complexes with many transition metal ions. These compounds are readily soluble
in organic solvents. They are widely used as chelating agents, ligands, and
Acetoacetic acid and its esters contain active
methylene groups which have relatively acidic alpha-protons due to H atom
adjacent to two carbonyl groups. The reactivity of its methylene group provide
the sequence of reactions of alkylation, hydrolysis of the esters and
decarboxylation resulting in substituted ketones. The methylene group can be
reacted to form amino-carbonyl compounds.
are important aliphatic parts adjoining azo dyes and pigments. Acetoacetic acid is unstable and
decompose to acetone and carbon dioxide at room temperature.
Aacetoacetate is one
of ketone bodies which are the end-products of rapid or excessive fatty acid
breakdown in the human body.
Para-benzoquinone and its
derivatives belong to 1,4-diketone family. Benzoquinone is used as
an oxidizing agent in organic chemistry and is a common constituent of
biologically molecules like Vitamin K1. Quinones serves as electron acceptors in
electron transport chains such as in photosynthesis, and aerobic respiration.
Diketene derivatives find versatile applications in
making biomolecules, agrochemicals, dyes, pigments, pharmaceuticals including
vitamins, and stabilizers for PVC and polyester. They are used as components for
fragrances and as solvents. Diketones undergo the reversible and
irreversible addition reactions include;
of Enolate Anions
and Acetal Formation
- Wolff-Kishner Reduction
(2,4-pentanedione) is a clear to slightly yellowish liquid; melting point
–23 C, boiling point 139 C. It is readily soluble in water and in organic solvents.
The keto form (CH2COCH2COCH3)
and enol form
(CH3COCH=C(OH)CH3) coexist in solution.
This enol-keto tautomerism
(reversible interconversion of structural isomers) results in the tautomeric migration of a hydrogen atom from an
adjacent carbon atom to a carbonyl group of a keto compound to produce the enol
form of the compound; the reverse migration of hydrogen atom is also
interconvertible, which makes the switch of a single bond and adjacent double bond.
is used in the production of anti-corrosion agents and its peroxide compounds
for the radical initiator application for polymerisation.
It is used as a chemical intermediate for drugs (such
as sulfamethazine, nicarbazine, vitamin B6 and vitamin K)
and pesticides (such as sulfonylurea herbicides). Very strong bases can deprotonate two carbonyl groups
and results in alkylation at C1. Arylation can be obtained
by substitution of halides on benzoic acid. Acetylacetone is converted
to heterocycles (isoxazoles, pyrazoles,pyrimidines, pyridines
etc); to pyrazoles with hydrazine and to pyrimidines
with urea. Acetylacetone condenses with amines to give
diketimines. It is used as a solvent for cellulose acetate, as
an additive in gasoline and
lubricant, as a dryer of paint and varnish. It is used as an indicator for the complexometric titration of Fe(III)
and for the
modification of guanidino groups and amino
groups in proteins.
is used in the preparation of metal acetylacetonates for
catalyst application. The oxygen
atoms in delocalized anion (acetylacetonate) left after the removal of a proton
from an enol
is readily bound to transition metal ions and form chelate
complexes which is freely soluble organic solvents,
in contrast to the related metal halides. Metal acetylacetonate
complexes are widely used as catalysts and reagents.