Hexane-2,5-dione

2,5-Hexanedione (Acetonylacetone) is an aliphatic diketone. It is a colorless liquid.[1] In humans, it is a toxic metabolite of hexane and of 2-hexanone.

Not to be confused with Acetylacetone.
Hexane-2,5-dione
Names
Preferred IUPAC name
Hexane-2,5-dione
Other names
1,2-Diacetylethane
'α','β'-Diacetylethane
Acetonyl acetone
Diacetonyl
2,5-Dioxohexane
2,5-Diketohexane
2,5-Hexanedione
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.003.400
EC Number
  • 203-738-3
RTECS number
  • MO3150000
UNII
UN number 1224
Properties
C6H10O2
Molar mass 114.1438 g mol−1
Appearance colorless liquid
Density 0.973 g cm−3, liquid
Melting point −5.5 °C (22.1 °F; 267.6 K)
Boiling point 191.4 °C (376.5 °F; 464.5 K)
≥ 10 g/100 mL (22 °C)
-62.51·10−6 cm3/mol
Structure
trigonal planar at carbonyl
tetrahedral elsewhere
Hazards
GHS pictograms
GHS Signal word Warning
GHS hazard statements
 H315, H319, H373
P260, P264, P280, P302+352, P305+351+338, P314, P321, P332+313, P337+313, P362, P501
Flash point 78 °C (172 °F; 351 K)
Related compounds
Related diketones
 acetylacetone
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Symptoms of poisoning

The chronic toxicity of hexane is attributed to hexane-2,5-dione. The symptoms are tingling and cramps in the arms and legs, followed by general muscular weakness. In severe cases, atrophy of the skeletal muscles is observed, along with a loss of coordination and vision problems.[2]

Similar symptoms are observed in animal models. They are associated with a degeneration of the peripheral nervous system (and eventually the central nervous system), starting with the distal portions of the longer and wider nerve axons.

Mechanism of action

It appears that the neurotoxicity of 2,5-hexanedione resides in its γ-diketone structure since 2,3-, 2,4-hexanedione and 2,6-heptanedione are not neurotoxic, whereas 2,5-heptanedione and 3,6-octanedione and other γ-diketones are.[3]

2,5-Hexanedione reacts with lysine residues in axonal proteins by Schiff base formation followed by cyclization to give pyrroles. Oxidation of the pyrrole residues then causes cross-linking and denaturation of proteins, which perturbs axonal transport and function and causes damage to nerve cells.[4]

Synthesis

2,5-Hexanedione has been prepared in several ways.[5] A common method involves hydrolysis of 2,5-dimethylfuran, a glucose derived heterocycle.[1]

Uses

Acetonylacetone can be used in the synthesis of isocarboxazid,[6] rolgamidine,[7] and mopidralazine. Treatment with P4S10 gives 2,5-dimethylthiophene.

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References
  1. Young, D. M.; Allen, C. F. H. (1936). "2,5-Dimethylpyrrole". Organic Syntheses. 16: 25. doi:10.15227/orgsyn.016.0025.
  2. Couri D, Milks M. "Toxicity and metabolism of the neurotoxic hexacarbons n-hexane, 2-hexanone, and 2,5-hexanedione" Annu. Rev. Pharmacol. Toxicol. 1982;22:145-66.
  3. Stephen R Clough; Leyna Mulholland (2005), "Hexane", Encyclopedia of Toxicology, 2 (2nd ed.), Elsevier, pp. 522–525
  4. Wolfgang Dekant; Spiridon Vamvakas (2007). "Toxicology". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. p. 23.
  5. http://www.prepchem.com/synthesis-of-2-5-hexanedione/ Primary: Systematic organic chemistry, by W. M. Cumming, 194, 1937.
  6. U.S. Patent 2,908,688
  7. U.S. Patent 4,140,793
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