The Collaborative Dictionary

Xylene \Xy"lene\, n. [Gr. xy`lon wood.] (Chem.) Any of a group of three metameric hydrocarbons of the aromatic series, found in coal and wood tar, and so named because found in crude wood spirit. They are colorless, oily, inflammable liquids, C6H4.(CH3)2, being dimethyl benzenes, and are called respectively orthoxylene, metaxylene, and paraxylene. Called also xylol. [1913 Webster] Note: Each of these xylenes is the nucleus and prototype of a distinct series of compounds. [1913 Webster]

Word Net

xylene n : a colorless flammable volatile liquid hydrocarbon used as a solvent [syn: xylol]

English

Etymology

From ‘wood’ + -ene.

Pronunciation

/ˈzaɪliːn/

Noun

1. Any of a group of three isomeric aromatic hydrocarbons, di-methyl-benzene, found in coal and wood tar.
   • 2006, Thomas Pynchon, Against the Day, Vintage 2007, p. 262:

     [...] proceeding, desperately, from such opiated catarrh preparations as Collis Brown's Mixture on to cocainized brain tonics, cigarettes soaked in absinthe, xylene in unventilated rooms, and so on [...].

Translations

The term xylene or xylol refers to a mixture of three benzene derivatives which is used as a solvent in the printing, rubber, and leather industries. Xylene is a colorless, sweet-smelling liquid that is very flammable. Like other solvents, xylene is also used as an inhalant drug for its intoxicating properties.

Chemical properties

Xylene is a generic term for a group of three benzene derivatives which encompasses ortho-, meta-, and para- isomers of dimethyl benzene. The o-, m- and p- designations specify to which carbon atoms (of the benzene ring) the two methyl groups are attached. Counting the carbon atoms from one of the ring carbons bonded to a methyl group, and counting towards the second ring carbon bonded to a methyl group, the o- isomer has the IUPAC name of 1,2-dimethylbenzene, the m- isomer has the IUPAC name of 1,3-dimethylbenzene, and the p- isomer has the IUPAC name of 1,4-dimethylbenzene. Solvent grade xylene usually contains a small percentage of ethylbenzene as a contaminent.

The chemical properties differ slightly from isomer to isomer. The melting point is between (m-xylene) and (p-xylene). The boiling point for each isomer is around . The density is at around 0.87 kg/L (7.26 lb/U.S. gallon or 8.72 lb/imp gallon) and thus is less dense than water. Xylene in air can be smelled at 0.08 to 3.7 parts of xylene per million parts of air (ppm) and can begin to be tasted in water at 0.53 to 1.8 ppm.

Applications

Xylene is used as a solvent and in the printing, rubber, and leather industries. p-Xylene is used as a feedstock in the production of terephthalic acid, which is a monomer used in the production of polymers. It is also used as a cleaning agent for steel and for silicon wafers and chips, a pesticide http://www.cdpr.ca.gov/cgi-bin/epa/chemdet.pl?pccode=086803, a thinner for paint, and in paints and varnishes. It may be substituted for toluene to thin lacquers where slower drying is desired. It is found in small amounts in airplane fuel and gasoline. In animal studies it is often swabbed on the ears of rabbits to facilitate blood flow and collection, although the area must subsequently be cleansed with alcohol to prevent inflammation. Xylene is also used as a fixation agent for animal tissues.

Related compounds

Xylenes are a starting material for the production of other chemicals. For instance chlorination of both methyl groups gives three isomeric xylene dichlorides or 1,2-bis(chloromethyl)benzenes. With oxidizing agents, such as potassium permanganate (KMnO4), the methyl group can be oxidized to a carboxylic acid. By oxidizing both methyl groups, o-xylene forms phthalic acid and p-xylene forms terephthalic acid.

In articles of commerce, the term xylol refers to the solvent mixture of three xylene isomers, sometimes containing ethylbenzene. In the chemical trade, this mixture is referred to as xylenes (plural). This substance must not be confused with the toxic and corrosive xyleneol compounds, which are dimethyl phenol isomers.

Health effects

Xylene has an effect on the brain. High levels from exposure for short periods (14 days or less) or long periods (more than 1 year) can cause headaches, lack of muscle coordination, dizziness, confusion, and changes in one's sense of balance. Exposure of people to high levels of xylene for short periods can also cause irritation of the skin, eyes, nose, and throat; difficulty in breathing; problems with the lungs; delayed reaction time; memory difficulties; stomach discomfort; and possibly changes in the liver and kidneys. It can cause unconsciousness and even death at very high levels (see inhalants).

Studies of unborn animals indicate that high concentrations of xylene may cause increased numbers of deaths, and delayed growth and development. In many instances, these same concentrations also cause damage to the mothers. It is not yet known whether xylene harms the unborn fetus if the mother is exposed to low levels of xylene during pregnancy

Besides occupational exposure, the principal pathway of human contact is via soil contamination from leaking underground storage tanks containing petroleum products. Humans who come into contact with the soil or groundwater may become affected. Use of contaminated groundwater as a water supply could lead to adverse health effects.

See also

• Water pollution
• Toxicity
• Gasoline

External links

• International Chemical Safety Card 0084 (o-Xylene)
• International Chemical Safety Card 0085 (m-Xylene)
• International Chemical Safety Card 0086 (p-Xylene)
• NIOSH Pocket Guide to Chemical Hazards (o-Xylene)
• NIOSH Pocket Guide to Chemical Hazards (m-Xylene)
• NIOSH Pocket Guide to Chemical Hazards (p-Xylene)