M-xylene

<i>m</i>-Xylene

m-Xylene

Chemical compound

m-Xylene (meta-xylene) is an aromatic hydrocarbon. It is one of the three isomers of dimethylbenzene known collectively as xylenes. The m- stands for meta-, indicating that the two methyl groups in m-xylene occupy positions 1 and 3 on a benzene ring. It is in the positions of the two methyl groups, their arene substitution pattern, that it differs from the other isomers, o-xylene and p-xylene. All have the same chemical formula C6H4(CH3)2. All xylene isomers are colorless and highly flammable.[6]

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Production and use

Petroleum contains about 1 weight percent xylenes.[7] The meta isomer can be isolated from a mix of xylenes by the partial sulfonation (to which other isomers are less prone) followed by removal of unsulfonated oils and steam distillation of the sulfonated product.

The major use of meta-xylene is in the production of isophthalic acid, which is used as a copolymerizing monomer to alter the properties of polyethylene terephthalate. The conversion m-xylene to isophthalic acid entails catalytic oxidation. meta-Xylene is also used as a raw material in the manufacture of 2,4- and 2,6-xylidine as well as a range of smaller-volume chemicals.[8][6] Ammoxidation gives isophthalonitrile.

Toxicity and exposure

Xylenes are not acutely toxic, for example the LD50 (rat, oral) is 4300 mg/kg. Effects vary with animal and xylene isomer. Concerns with xylenes focus on narcotic effects.[6]

See also

References

  1. [1]
    Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. p. 139. doi:10.1039/9781849733069. ISBN 978-0-85404-182-4.
  2. [2]
    NIOSH Pocket Guide to Chemical Hazards. "#0669". National Institute for Occupational Safety and Health (NIOSH).
  3. [3]
    DeanHandb, Lange´s Handbook of chemistry, 15th edition,1999.
  4. [4]
    "m-Xylene". International Chemical Safety Cards. IPCS/NIOSH. July 1, 2014. Archived from the original on December 5, 2017. Retrieved September 9, 2017.
  5. [5]
    "Xylene (o-, m-, p-isomers)". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  6. [6]
    Fabri, Jörg; Graeser, Ulrich; Simo, Thomas A. (2000). "Xylenes". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a28_433. ISBN 978-3527306732.
  7. [7]
    EPA-454/R-93-048 Locating and estimating air emissions from sources of xylene Emission Inventory Branch Technical Support Division Office of Air Quality Planning and Standards U.S. Environmental Protection Agency March 1994
  8. [8]
    Ashford's Dictionary of Industrial Chemicals, third edition, page 9692.
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