View source for Xylene

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{{see also|o-Xylene|m-Xylene|p-Xylene}}

==Overview==

The term '''xylenes''' refers to a group of 3 [[benzene]] derivatives which encompasses ''ortho''-, ''meta''-, and ''para''- [[isomer]]s of dimethyl benzene. The ''o''-, ''m''- and ''p''- isomers specify to which [[carbon]] atoms (of the main [[benzene ring]]) the two [[methyl]] groups are attached. Counting the [[carbon]] [[atom]]s 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 ''p''- isomer has the IUPAC name of 1,4-dimethylbenzene.

[[Image:Iupac-cyclic.png|center|The xylene isomers]]


It is a colorless, sweet-smelling liquid that is very flammable. It occurs naturally in [[petroleum]] and [[coal tar]] and is formed during forest fires. The chemical properties differ slightly from isomer to isomer. The melting point is between {{convert|-47.87|°C|°F|2}} (''m''-xylene) and {{convert|13.26|°C|°F|2}} (''p''-xylene). The boiling point is for each isomer at around {{convert|140|°C|°F|2}}. The density is at around 0.87 kg/L (7.26&nbsp;[[Pound (mass)|lb]]/U.S.&nbsp;gallon or 8.72&nbsp;lb/[[Imperial gallon|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.

Chemical industries produce xylene from petroleum. It is one of the top 30 chemicals produced in the United States in terms of volume. 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 [[polymer]]s. It is also used as a cleaning agent for [[steel]] and for [[silicon wafer]]s and [[integrated circuit|chip]]s, a [[pesticide]] [http://www.cdpr.ca.gov/cgi-bin/epa/chemdet.pl?pccode=086803], a [[paint thinner|thinner for paint]], and in [[paint]]s and [[varnish]]es.  It may be substituted for [[toluene]] to thin lacquers where slower drying is desired. It is found in small amounts in [[jet fuel|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.

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! {{chembox header}} align="center" colspan="5" | Xylenes and Its Isomers
|-
<!--| align="center" colspan="5" | [[Image:Xylene Isomers.PNG|400px|{{PAGENAME}}]] replace if not identical with the pagename -->
|-
! {{chembox header}} align="center" colspan="5" | General
|- 
| Common name
| '''Xylenes'''
| '''''o''-Xylene'''
| '''''m''-Xylene'''
| '''''p''-Xylene'''
|-
| [[IUPAC nomenclature|Systematic name]]
| Dimethylbenzenes
| 1,2-Dimethylbenzene
| 1,3-Dimethylbenzene
| 1,4-Dimethylbenzene
|-
| Other names
| Xylols
| ''o''-Xylol;<br>Orthoxylene
| ''m''-Xylol;<br>Metaxylene
| ''p''-Xylol;<br>Paraxylene
|-
| [[Chemical formula|Molecular formula]]
| align="center" colspan="4" | C<sub>8</sub>H<sub>10</sub>
|-
| [[Simplified molecular input line entry specification|SMILES]]
| 
| Cc1c(C)cccc1
| Cc1cc(C)ccc1 
| Cc1ccc(C)cc1
|-
| [[Molar mass]]
| align="center" colspan="4" | 106.16 g/mol
|-
| Appearance
| align="center" colspan="4" | clear, colorless liquid
|-
| [[CAS registry number|CAS number]]
| [1330-20-7]
| [95-47-6]
| [108-38-3]
| [106-42-3]
|-
! {{chembox header}} align="center" colspan="5" | Properties
|-
| [[Density]] and [[Phase (matter)|phase]]
| 0.864 g/mL, liquid
| 0.88 g/mL, liquid
| 0.86 g/mL, liquid
| 0.86 g/mL, liquid
|-
| [[Soluble|Solubility]] in [[Water (molecule)|water]]
| align="center" colspan="4" | practically insoluble
|-
| align="center" colspan="5" | Soluble in non-polar [[solvent]]s such as [[aromatic]] [[hydrocarbon]]s
|-
| [[Melting point]]
| -47.4°C (-53.3°F; 226 K)
| −25°C (-13°F; 248 K)
| −48°C (-54.4°F; 225 K)
| 13°C (55.4°F; 286 K)
|-
| [[Boiling point]]
| 138.5°C (281.3°F; 412 K)
| 144°C (291.2°F; 417 K)
| 139°C (282.2°F; 412 K)
| 138°C (280.4°F; 411 K)
|-
| [[Viscosity]]
| 
| .812 c[[Poise|P]] at {{convert|20|°C|°F|0}}
| .62 c[[Poise|P]] at {{convert|20|°C|°F|0}}
| .34 c[[Poise|P]] at {{convert|30|°C|°F|0}}
|-
! {{chembox header}} align="center" colspan="5" | Hazards <!-- Summary only- MSDS entry provides more complete information -->
|-
| [[Material safety data sheet|MSDS]]
| [http://sciencelab.com/msds.php?msdsId=9927646 Xylenes]
| [http://sciencelab.com/msds.php?msdsId=9927647 ''o''-Xylene]
| [http://sciencelab.com/msds.php?msdsId=9927323 ''m''-Xylene]
| [http://sciencelab.com/msds.php?msdsId=9927324 ''p''-Xylene]
|-
| [[Directive 67/548/EEC|EU Classification]]
| align="center" colspan="4" | Harmful ('''Xn''')
|-
| [[NFPA 704]]
| align="center" colspan="4" | {{ NFPA 704 | Health=2 | Flammability=3 | Reactivity=0 }}
|-
| [[Flash point]]
| {{convert|24|°C|°F|0}}
| {{convert|17|°C|°F|0}}
| {{convert|25|°C|°F|0}}
| {{convert|25|°C|°F|0}}
|-
| [[Risk and Safety Statements|R/S statement]]
| align="center" colspan="4" | {{R10}}, {{R20/21}}, {{R38}}: {{S2}}, {{S25}}
|-
| [[RTECS]] number
| 
| ZE2450000
| ZE2275000
| ZE2625000
|-
! {{chembox header}} align="center" colspan="5" | Supplementary data page
|-
| Structure & properties 
| align="center" colspan="4" | [[Refractive index|''n'']], [[Dielectric constant|''ε<sub>r</sub>'']], etc. 
|-
| Thermodynamic data 
| align="center" colspan="4" | Phase behaviour<br>Solid, liquid, gas
|-
| Spectral data
| align="center" colspan="4" | [[UV/VIS spectroscopy|UV]], [[Infrared spectroscopy|IR]], [[NMR spectroscopy|NMR]], [[Mass spectrometry|MS]]
|-
! {{chembox header}} align="center" colspan="5" | Related compounds
|-
| Related [[aromatic]]<br>[[hydrocarbon]]s
| align="center" colspan="4" | [[toluene]], [[mesitylene]], [[benzene]], [[ethylbenzene]]
|-
| Related compounds 
| align="center" colspan="4" | xylenols - types of [[phenols]]
|-
| {{chembox header}} align="center" colspan="5" | <small>Except where noted otherwise, data are given for<br> materials in their [[standard state|standard state (at 25°C, 100 kPa)]]<br/>[[wikipedia:Chemical infobox|Infobox disclaimer and references]]</small>
|-
|}

==Related compounds==
Xylenes are a starting material for the production of other chemicals. For instance [[chlorination]] gives a '''xylylene dichlorides''' or 1,2-bis(chloromethyl)benzene (again three possible isomers). With oxidizing agents, such as [[potassium permanganate]] (KMnO<sub>4</sub>), the methyl group can be oxidized to a [[carboxylic acid]]. By oxidizing both methyl groups towards the acid, ''o''-xylene forms [[phthalic acid]], whereas ''p''-xylene forms [[terephthalic acid]].  

==Health effects==
Xylene affects 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 hygiene|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. 

Another common form of human exposure to xylene is in the use of certain types of pens, writing and drawing instruments, bingo dabbers and art supplies.

==See also==
*[[Water pollution]]
*[[Toxicity]]
*[[Gasoline]]

== External links ==
*[http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc00/icsc0084.htm International Chemical Safety Card 0084] (''o''-Xylene)
*[http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc00/icsc0085.htm International Chemical Safety Card 0085] (''m''-Xylene)
*[http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc00/icsc0086.htm International Chemical Safety Card 0086] (''p''-Xylene)
*[http://www.cdc.gov/niosh/npg/npgd0668.html NIOSH Pocket Guide to Chemical Hazards] (''o''-Xylene)
*[http://www.cdc.gov/niosh/npg/npgd0669.html NIOSH Pocket Guide to Chemical Hazards] (''m''-Xylene)
*[http://www.cdc.gov/niosh/npg/npgd0670.html NIOSH Pocket Guide to Chemical Hazards] (''p''-Xylene)
*{{ecb}}

<br>

[[Category:Aromatic hydrocarbons]]
[[Category:Hazardous air pollutants]]
[[Category:Soil contamination]]
[[Category:Hydrocarbon solvents]]

[[cs:Xylen]]
[[da:Xylen]]
[[de:Xylol]]
[[es:Xileno]]
[[fr:Xylène]]
[[it:Xilene]]
[[lv:Ksilols]]
[[lt:Ksilenas]]
[[nl:Xyleen]]
[[ja:キシレン]]
[[no:Xylen]]
[[pl:Ksyleny]]
[[pt:Xileno]]
[[ru:Диметилбензол]]
[[fi:Ksyleeni]]
[[sv:Xylen]]
[[vi:Xylen]]
[[zh:二甲苯]]

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