2,3,4-Pentanetrione (or IUPAC name pentane-2,3,4-trione, triketopentane or dimethyl triketone) is the simplest linear triketone, a ketone with three C=O groups. It is an organic molecule with formula CH<sub>3</sub>COCOCOCH<sub>3</sub>.
2,3,4-Pentanetrione can be made by oxidizing 2,4-pentanedione with selenium dioxide. Ludwig Wolff made the 2,3 oxime by reacting hydroxylamine with isonitrosoacetylacetone in cold, aqueous, concentrated solution.
Yet other ways to make triones start from a ò-dione, and oxidise the carbon at the ñ position, between the two ketone groups. Different methods include reaction with bromine to make a dibromide, and then reacting with acetaldehyde and hydrolysing. Nitrogen oxides can also be used. Another way is by reacting 2,4-pentandedione with p-nitroso-N,N-dimethylaniline; forming an ñ-diazo-ò-dicarbonyl derivative compound, and then reacting that with triphenylphosphine, and then hydrolyzing with sodium nitrite solution. Or the ñ-diazo-ò-dicarbonyl derivative can be treated with tert-butylhypochlorite.
2,3,4-Pentanetrione appears as an orangy-red oil. The more intense colour is due to the greater conjugation of double bonds, and potential resonance. The type of colour centre is called a dependent chromophore, as when there are fewer C=O groups the colour is less intense or absent. So diacetyl with two carbonyls groups is yellow, and acetone with one has no colour.
At a reduced pressure of 20 mmHg it boils at 60 ðC. It is hygroscopic.
The odour is strong and not bad.
On absorbing water, perhaps from the atmosphere, 2,3,4-pentanetrione forms a hydrate. The hydrate melts at 52 ðC. The hydrate with formula CH<sub>3</sub>COC(OH)<sub>2</sub>COCH<sub>3</sub> is colourless.
2,3,4-Pentanetrione is a strong reducing agent. Thermal decomposition catalyzed by copper sulfate results in carbon dioxide and diacetyl.
2,3,4-Pentanetrione reacts with hydrogen peroxide to yield acetic acid and carbon monoxide. Adding HOOH between C2 and C4 yields a cyclic intermediate which decomposes.
With light or organic peroxides, a free radical reaction can take place (as with triketones), whereby the molecule is slit into CH<sub>3</sub>COCO<sup>â¢</sup> and CH<sub>3</sub>CO<sup>â¢</sup> fragments. These can combine with intact molecules or each other to form other ketones.
When heating 2,3,4-pentanetrione with oxygen, the oxidation products are diacetyl, acetic acid, water and carbon dioxide.
Alkalis convert it into acetic acid and formaldehyde.
2,3,4-Pentanetrione does a condensation reaction with o-phenylenediamine to yield methyl-quinoxaline-2-methylketone, a heterocyclic dicycle. In this the carbon number 2 and 3 react with the amine groups, leaving the CO on number 5 alone.
Another condensation can happen with 2,5,6-triamino-4(3H)pyrimidinone giving 6-acetyl-2-amino-7-methyl-4(3H)pteridinone.
Grignard agents react. Phenyl magnesium bromide in excess reacting with 2,3,4-pentanetrione gives phenylacetylcarbinol and also methyldiphenylcarbinol.
Derivatives include 2,3,4-pentanetrione-3-oxime, 2,3,4-pentanetrione-3-(O-methyloxime), 2,3,4-pentanetrione-2-oxime, 2,3,4-pentanetrione-2,3-dioxime, 2,3,4-pentanetrionetrioxime, 2,3,4-pentanetrione semicarbazone, 2,3,4-pentanetrione phenylhydrazone, 2,3,4-pentanetrione bis(phenylhydrazone).
The 3-oxime melts at 75 ðC and the bis(semicarbazone) has a melting point of 221 ðC.