Xylene

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Xylene
Xylene isomers.png
The three xylene isomers.
Names
IUPAC name
Dimethylbenzene
Other names
Methyltoluene
Xylol
Properties
C8H10
C6H4(CH3)2
Molar mass 318.504 g/mol
Appearance Colorless liquid
Odor Sweet, paint thinner-like
Density 0.864 g/mL
Melting point −47.4 °C (−53.3 °F; 225.8 K)
Boiling point 138.5 °C (281.3 °F; 411.6 K)
0.0106 g/100 ml (25 °C)
Solubility Miscible with acetone, benzene, diethyl ether, esters, ethanol, toluene
Vapor pressure 6.65-8.80 mmHg (25 °C)
Hazards
Safety data sheet Sigma-Aldrich (mixture)
Sigma-Aldrich (ortho)
Sigma-Aldrich (meta)
Sigma-Aldrich (para)
Flash point 30 °C (86 °F; 303 K)
Related compounds
Related compounds
Benzene
Toluene
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Xylene is an aromatic hydrocarbon consisting of a benzene ring with two methyl substituents. Xylene consists of three isomers: ortho-xylene, meta-xylene and para-xylene, each having a molecular formula C8H10 or, because it's an aromatic compound, C6H4(CH3)2.

Properties

Chemical

Xylene can be nitrated to give mono-, di-, trinitroxylene (TNX), using a mixture of sulfuric and nitric acid.

Physical

All three isomers of xylene are liquid at room temperature and have a characteristic paint thinner smell. The melting point of the three isomers ranges is −25 °C for o-xylene, −47.87 °C for m-xylene and 13.26 °C for p-xylene. The boiling point for each isomer is 144 °C for o-xylene, 139 °C for m-xylene and 138 °C for p-xylene. The density of each is around 0.88 g/mL for o-xylene and 0.86 g/ml for meta and p-xylene.

Availability

Xylene is available as a paint thinner, either pure or mixed with other low chain hydrocarbons, as well as traces of butanol or butyl acetate and it's always a mixture of the three isomers. It can also be carefully removed from mixed solvents commonly found in hardware stores by fractional distillation. Individual isomers can be purchased from chemical suppliers, though they aren't cheap. Because the boiling point of the three isomers is very close, it's extremely difficult to separate the three isomers via fractional distillation.

Preparation

Xylene can be prepared by methylating toluene, a process that yields all the three isomers.

Projects

Handling

Safety

Xylene is an irritant to eyes, nose and lungs. It has low toxicity and low carcinogenic potential. Xylene is flammable and should be handled with care.

Storage

Xylene should be stored in closed bottles, away from any source of heat and light.

Disposal

Xylene can be burned, though this will generate lots of carbon monoxide, soot, VOCs, PAHs, as well as unburnt xylene. If you really want to do burn it, do it outside, away from people. Try not to burn too much xylene at once, and instead burn it in small amounts over a longer period of time, preferably diluted with a more "clean" burning solvent, like (denaturated) alcohol.

As it is an aromatic compound, Fenton's reagent can also be used. While the oxidation doesn't produce harmful products, the process produces lots of gasses which will aerosolize some of the unoxidized xylene, as well as other intermediate products into the air. This is dangerous in an enclosed area, carrying both a fire/explosion hazard as well as inhaling irritant xylene vapors. To reduce this unpleasant effect, xylene should be added dropwise or bubbled through a gas diffusing stone in the Fenton solution to limit vapor escape. The neutralization should be performed in a fumehood, well ventilated area or outside. Using a UV lamp will improve the speed of decomposition.[1]

References

  1. http://online.liebertpub.com/doi/abs/10.1089/hwm.1995.12.185?journalCode=hwm

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