P-Xylene: Difference between revisions

|Verifiedfields = changed

|Watchedfields = changed

|verifiedrevid = 415835068

|Name = ''p''-Xylene

|ImageFile = Para-Xylol - para-xylene.svg

|ImageName = Skeletal formula

|ImageCaption = [[Skeletal formula]]

|ImageSize = 180px

|ImageFile1 = p-xylene-spaceFilling.png

|ImageSize1 = 150px

|ImageName1 = Space-filling model

|ImageCaption1 = Space-filling model

|PIN = 1,4-Xylene<ref name=iupac2013>{{cite book | title = Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book) | publisher = [[Royal Society of Chemistry|The Royal Society of Chemistry]] | date = 2014 | location = Cambridge | page = 139 | doi = 10.1039/9781849733069 | isbn = 978-0-85404-182-4}}</ref>

|SystematicName = 1,4-dimethylbenzene

|OtherNames = ''p''-Xylene, ''p''-dimethylbenzene; ''p''-xylol; 1,4-xylene; ''p''-methyltoluene;<ref>Not to be used</ref> paraxylene; chromar; scintillar; 4-methyltoluene;<ref>Archaic name</ref> NSC 72419; or 1,4-dimethylbenzene.<ref name=NIST>{{cite web|title=p-xylene|url=http://webbook.nist.gov/cgi/cbook.cgi?ID=C106423&Mask=200|publisher=NIST|access-date=21 February 2013}}</ref>

|Section1 = {{Chembox Identifiers

|CASNo_Ref = {{cascite|correct|CAS}}

|CASNo = 106-42-3

|Beilstein = 1901563

|ChEBI_Ref = {{ebicite|correct|EBI}}

|ChEBI = 27417

|ChEMBL_Ref = {{ebicite|correct|EBI}}

|ChEMBL = 31561

|ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

|ChemSpiderID = 7521

|EINECS = 203-396-5

|Gmelin = 2697

|KEGG_Ref = {{keggcite|correct|kegg}}

|KEGG = C06756

|PubChem = 7809

|RTECS = ZE2625000

|UNII_Ref = {{fdacite|correct|FDA}}

|UNII = 6WAC1O477V

|SMILES = CC1=CC=C(C)C=C1

|InChI = 1/C8H10/c1-7-3-5-8(2)6-4-7/h3-6H,1-2H3

|InChIKey = URLKBWYHVLBVBO-UHFFFAOYAE

|StdInChI_Ref = {{stdinchicite|changed|chemspider}}

|StdInChI = 1S/C8H10/c1-7-3-5-8(2)6-4-7/h3-6H,1-2H3

|StdInChIKey_Ref = {{stdinchicite|changed|chemspider}}

|StdInChIKey = URLKBWYHVLBVBO-UHFFFAOYSA-N

}}

|Section2 = {{Chembox Properties

|Appearance = Colorless liquid

|C=8 | H=10

|BoilingPtC = 138.35

|Odor = Aromatic<ref name=PGCH/>

|MeltingPtC = 13.2

|Density = 0.861 g/mL

|RefractIndex = 1.49582

|Solubility = Insoluble

|Solubility1 = Very soluble

|Solvent1 = ethanol

|Solubility2 = Very soluble

|Solvent2 = diethyl ether

|Viscosity = 0.7385 c[[Poise (unit)|P]] at 0 °C<br>0.6475 c[[Poise (unit)|P]] at 20 °C

|Dipole = 0.00 [[Debye|D]]<ref>Perry's Handbook of Chemical Engineers</ref>

|VaporPressure = 9 mmHg (20°C)<ref name=PGCH/>

|MagSus = -76.78·10⁻⁶ cm³/mol

}}

|Section3 = {{Chembox Hazards

|ExternalSDS = [http://www.jtbaker.com/msds/englishhtml/x2600.htm External MSDS]

|FlashPtC = 27

|FlashPt_ref = <ref name=ICSC/>

|MainHazards = Harmful or if swallowed. Vapor maybe toxic.<ref>P-Xylene: main hazards</ref> Flammable liquid and vapor.

|NFPA-H = 2

|NFPA-F = 3

|NFPA-R = 0

|GHSPictograms = {{GHS02}}{{GHS07}}{{GHS08}}

|GHSSignalWord = Danger

|HPhrases = {{H-phrases|226|302|304|312|315|319|332|335|412}}

|PPhrases = {{P-phrases|210|233|240|241|242|243|261|264|271|273|280|301+310|302+352|303+361+353|304+312|304+340|305+351+338|312|321|322|331|332+313|337+313|362|363|370+378|403+233|403+235|405|501}}

|PEL = TWA 100 ppm (435 mg/m³)<ref name=PGCH>{{PGCH|0670}}</ref>

|ExploLimits = 1.1%-7.0%<ref name=PGCH/>

|LC50 = 4550 ppm (rat, 4 hr)<ref name=IDLH>{{IDLH|95476|Xylenes}}</ref>

|REL = TWA 100 ppm (435 mg/m³) ST 150 ppm (655 mg/m³)<ref name=PGCH/>

|TLV-TWA = 100 ppm<ref name=ICSC>{{cite web |url = https://www.cdc.gov/niosh/ipcsneng/neng0086.html |title = p-Xylene |work = International Chemical Safety Cards |publisher = ICSC/NIOSH |date = July 1, 2014}}</ref>

|TLV-STEL = 150 ppm<ref name=ICSC/>

|IDLH = 900 ppm<ref name=PGCH/>

|AutoignitionPtC = 528

|AutoignitionPt_ref = <ref name=ICSC/>

|LD50 = 4300 mg/kg<ref>P-Xylene: toxicity for rats</ref>

|LCLo = 3401 ppm (mouse)<ref name=IDLH/>

}}

|Section4 = {{Chembox Related

|OtherFunction_label = [[aromatic hydrocarbon|aromatic<br />hydrocarbons]]

|OtherFunction = [[benzene]]<br />[[toluene]]<br />[[O-xylene|''o''-xylene]]<br />[[M-Xylene|''m''-xylene]]

}}

'''''p''-Xylene''' ('''[[Arene substitution pattern|''para'']]-xylene''') is an [[aromatic hydrocarbon]]. It is one of the three [[isomer]]s of [[xylene|dimethylbenzene]] known collectively as [[xylene]]s. The ''p-'' stands for ''para-'', indicating that the two methyl groups in ''p''-xylene occupy the diametrically opposite substituent positions 1 and 4. It is in the positions of the two methyl groups, their [[arene substitution pattern]], that it differs from the other isomers, [[o-Xylene|''o''-xylene]] and [[m-Xylene|''m''-xylene]]. All have the same chemical formula C₆H₄(CH₃)₂. All xylene isomers are colorless and highly flammable. The odor threshold of ''p''-xylene is 0.62 [[parts per million]] (ppm).<ref name=MSDS>{{cite web|title=p-Xylene MSDS|publisher=ScienceLab.com}}</ref>

==Production==

The production of ''p''-xylene is industrially significant, with annual demand estimated at 37 million tons in 2014, and still on the increase.<ref name="Ullmann">{{cite book |url= |title=Ullmann's Encyclopedia of Industrial Chemistry |last1=Fabri |first1=Jörg |last2=Graeser |first2=Ulrich |last3=Simo |first3=Thomas A. |publisher=Wiley Online Library |year=2000 |doi=10.1002/14356007 |isbn=9783527303854 }}</ref><ref>Nature 532,435–437 (28 April 2016) doi:10.1038/532435a</ref> ''p''-Xylene is produced by [[catalytic reforming]] of petroleum [[naphtha]] as part of the [[BTX (chemistry)|BTX]] aromatics (benzene, toluene and the xylene isomers) extracted from the catalytic reformate. The ''p''-xylene is then separated out in a series of distillation, adsorption or crystallization and reaction processes from the ''m''-xylene, ''o''-xylene, and [[ethylbenzene]]. Its melting point is the highest among this series of isomers, but simple crystallization does not allow easy purification due to the formation of [[Eutectic system|eutectic]] mixtures.

Such separation procedures are major cost factors in the production of ''p''-xylene, and the search for alternative methods continues. For example, a reverse-osmosis technique has been proposed to improve various aspects of the processes.<ref>{{cite journal|journal=Science|year=2016|volume=353|issue=6301|pages=804–7|doi=10.1126/science.aaf1343|pmid=27540170|title=Reverse osmosis molecular differentiation of organic liquids using carbon molecular sieve membrane|author1=Koh, D. Y.|author2=McCool, B. A.|author3=Deckman, H. W.|author4=Lively, R. P.|bibcode=2016Sci...353..804K|s2cid=9480478}}</ref>

==Industrial applications==

''p''-Xylene is an important chemical [[feedstock]]. Among other industrial applications, it is a raw material in the large scale synthesis of various [[polymer]]s. In particular it is a component in the production of [[terephthalic acid]] for [[polyester]]s such as [[polyethylene terephthalate]] (generally known as PET). It also may be polymerised directly to produce [[parylene]].

:[[Image:Oxidation p xylene.svg|200px|Terephthalic acid]]

==Toxicity and exposure==

Xylenes are not acutely toxic, for example the [[LD50|LD₅₀]] (rat, oral) is 4300 mg/kg. Effects vary with animal and xylene isomer.

Concerns with xylenes focus on narcotic effects. Overexposure of ''p''-xylene in humans can cause headache, fatigue, dizziness, listlessness, confusion, irritability, gastrointestinal disturbances including nausea and loss of appetite, flushing of the face, and a feeling of increased body heat. ''p''-Xylene vapor exposure over the recommended exposure limit of 100 parts per million (ppm) can cause irritation to eye, nose, and throat and possible chest tightening and an abnormal gait.<ref name=properties>{{cite web|title=Material Safety Data Sheet – Para-Xylene|url=http://siri.org/msds/mf/amoco/files/01263000.html|publisher=Amoco|access-date=13 February 2013|archive-url=https://web.archive.org/web/20160304000856/http://siri.org/msds/mf/amoco/files/01263000.html|archive-date=4 March 2016|url-status=dead}}</ref>

''p''-Xylene occurs naturally in petroleum and coal tar. It is emitted by most combustion sources, including automobile exhaust and [[tobacco smoke]].<ref>EPA-454/R-93-048

[https://www3.epa.gov/ttnchie1/le/xylene.pdf 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</ref>

===Inhalation===

Inhaling ''p''-xylene can cause dizziness, headache, drowsiness, and nausea. If exposure through inhalation occurs, first aid includes fresh air, rest and possible medical attention. Through the use of ventilation or breathing protection, exposure to ''p''-xylene through inhalation can be prevented.<ref name="Exposure">{{cite web|url=https://www.cdc.gov/niosh/ipcsneng/neng0086.html|title=para-Xylene|publisher=National Institute for Occupational Safety and Health|access-date=12 February 2013}}</ref>

===Skin===

Exposure of ''p''-xylene through the skin can cause dry skin and redness. If skin exposure occurs, first aid includes rinsing and then washing the affected area with soap and water as well as removing any contaminated clothing and thoroughly cleaning and drying before reuse. Exposure can be prevented through the use of protective gloves.<ref name=Exposure/>

===Eyes===

Exposure of ''p''-xylene to eyes can cause redness and pain. If eyes are exposed, first aid includes rinsing of the eyes with water for several minutes, removal of contact lenses if applicable, and medical attention. Eye exposure can be prevented through the use of safety glasses or safety goggles.<ref name=Exposure/>

===Ingestion===

Ingestion of ''p''-xylene can result in a burning sensation, abdominal pain, dizziness, drowsiness, headache, and nausea. If ''p''-xylene is ingested one's mouth should be rinsed and vomiting should not be induced. Further medical attention should be sought. Ingestion can be prevented by not eating, drinking, or smoking when working with ''p''-xylene.<ref name=Exposure/>

===Short-term exposure===

''p''-Xylene can cause issues with the central nervous system and if swallowed could cause chemical pneumonitis when breathed into the lungs.<ref name=Exposure />

===Long-term exposure===

Liquid ''p''-xylene exposure to the skin over long periods of time can remove the fat from the skin. The substance may also have effects on the [[central nervous system]]. Exposure can enhance hearing loss caused by noise exposure. Animal tests suggest that this substance could cause damage to human development and reproductive systems.<ref name=Exposure />

{{reflist}}

{{Hydrocarbons}}

[[Category:Alkylbenzenes]]

[[Category:C2-Benzenes]]

[[Category:IARC Group 3 carcinogens]]