View source for 1,4-Dichlorobenzene

{{chembox
| Watchedfields = changed
| verifiedrevid = 322203130
|   Name = 1,4-Dichlorobenzene
|   ImageFileL1 = 1,4-Dichlorobenzene.svg
|   ImageSizeL1 = 120px
|   ImageNameL1 = 1,4-Dichlorobenzene
|   ImageFileR1 = Para-dichlorobenzene-3D-balls.png
|   ImageSizeR1 = 100px
|   ImageNameR1 = Ball-and-stick model of 1,4-dichlorobenzene
|   IUPACName = 1,4-Dichlorobenzene
|   OtherNames = ''para''-Dichlorobenzene<br />''p''-Dichlorobenzene<br />p-DCB<br/>PDB<br/>Paramoth<br/>Para crystals<br/>Paracide
| Section1 = {{Chembox Identifiers
|   SMILES = ClC1=CC=C(Cl)C=C1
|   ChemSpiderID = 4523
| CASNo_Ref = {{cascite}}
| CASNo = 106-46-7
|   RTECS = CZ4550000
  }}
| Section2 = {{Chembox Properties
|   C=6|H=4|Cl=2
|   Density = 1.25&nbsp;g/cm³, solid
|   Solubility = 10.5&nbsp;mg/100&nbsp;mL (20&nbsp;°C)
|   MeltingPtC = 53.5
|   BoilingPtC = 174
  }}
| Section7 = {{Chembox Hazards
|   EUClass = {{Hazchem Xn}}<br />{{Hazchem N}}<br />[[Carcinogen|Carc. Cat. 3]]
|   NFPA-H = 2
|   NFPA-F = 2
|   NFPA-R =
|   RPhrases = {{R36}} {{R40}} {{R50/53}}
|   SPhrases = {{S2}} {{S36/37}} {{S46}} {{S60}} {{S61}}
|   FlashPt = 66&nbsp;°C
  }}
| Section8 = {{Chembox Related
|   OtherCpds = [[1,2-Dichlorobenzene]]<br />[[1,3-Dichlorobenzene]]
  }}
}}

'''1,4-Dichlorobenzene''' (''para''-dichlorobenzene,  ''p''-DCB, PDB) is an [[organic compound]] with the [[chemical formula|formula]] C<sub>6</sub>H<sub>4</sub>Cl<sub>2</sub>. This colourless [[solid]] has a strong [[odour]]. It consists of two [[chlorine]] atoms substituted at opposing sites on a [[benzene]] ring. ''p''-DCB is used a pesticide and a deodorant, most familiarly in [[mothball]]s in which it is a replacement for the more traditional [[naphthalene]].<ref name="orst">{{cite web |url= http://npic.orst.edu/capro/Mothballs1.pdf |title= National Pesticide Information Center - Mothballs Case Profile |accessdate= 2009-08-10 }}</ref> ''p''-DCB is also used as a precursor in the production of the polymer [[poly(p-phenylene sulfide)]].<ref name=Ross>Manfred Rossberg, Wilhelm Lendle, Gerhard Pfleiderer, Adolf Tögel, Eberhard-Ludwig Dreher, Ernst Langer, Heinz Rassaerts, Peter Kleinschmidt, Heinz Strack, Richard Cook, Uwe Beck, Karl-August Lipper, Theodore R. Torkelson, Eckhard Löser, Klaus K. Beutel, “Chlorinated Hydrocarbons” in Ullmann’s Encyclopedia of Industrial Chemistry, 2006 John Wiley-VCH: Weinheim. [[doi:10.1002/14356007.a06 233.pub2]]</ref>

==Production==
''p''-DCB is produced by [[chlorination]] of benzene using [[ferric chloride]] as a catalyst:
:C<sub>6</sub>H<sub>6</sub>  +  2 Cl<sub>2</sub>  →  C<sub>6</sub>H<sub>4</sub>Cl<sub>2</sub>  +  2 [[hydrogen chloride|HCl]]
The chief impurity is the 1,2 isomer. The compound can be purified by fractional crystallisation, taking advantage of its relatively high melting point of 53.5&nbsp;°C; the isomeric [[dichlorobenzene]]s and chlorobenzene melt well below room temperature.<ref name=Ross/>

==Uses==
=== Disinfectant, deodorant, and pesticide===
''p''-DCB is used to control [[moth]]s, [[mould]]s, and [[mildew]]. It finds use as a disinfectant<ref name=Ross/> in waste containers and restrooms and is the characteristic smell associated with [[urinal cake]]s. Its usefulness in these arises from ''p''-DCB's low solubility in water and its relatively high volatility: it [[sublimation (chemistry)|sublimes]] readily near room temperature.<ref name=Ross/>

===Precursor to other chemicals===
The chlorides on ''p''-DCB can be [[nucleophilic substitution|substituted]] with hydroxyl, amine, and sulfide groups. In a growing application, ''p''-DCB is the precursor to the high performance polymer [[poly(p-phenylene sulfide)]]:
:C<sub>6</sub>H<sub>4</sub>Cl<sub>2</sub>  +  Na<sub>2</sub>S   →  1/n [C<sub>6</sub>H<sub>4</sub>S]<sub>n</sub>  +  2 NaCl

==Environmental effects==
''p''-DCB is poorly soluble in water and is not easily broken down by soil organisms. Like many hydrocarbons, ''p''-DCB is lipophilic and will accumulate in the fatty tissues.

==Health effects==
The US [[Department of Health and Human Services]] (DHHS) and the [[International Agency for Research on Cancer]] (IARC) have determined that ''p''-DCB may reasonably be anticipated to be a [[carcinogen]], although there is no direct evidence.<ref>[http://monographs.iarc.fr/ENG/Classification/crthgr02b.php Group 2B: Possibly carcinogenic to humans], [[International Agency for Research on Cancer]]</ref> Animals given very high levels in water developed [[liver]] and [[kidney]] [[tumor]]s {{Citation needed|date=August 2009}}. The [[United States Environmental Protection Agency]] (EPA) has set a target maximum contaminant level of 75 micrograms of ''p''-DCB per liter of [[drinking water]] (75&nbsp;μg/L).<ref name="epa-water">{{cite web |url= http://www.epa.gov/ogwdw000/contaminants/dw_contamfs/p-dichlo.html |title= Consumer Factsheet on: PARA-DICHLOROBENZENE (p-DCB) |date= November 28, 2006 |accessdate= 2009-08-10 }}</ref> ''p''-DCB is also an EPA-registered pesticide.<ref name="epa-rereg">{{cite web |url= http://www.epa.gov/oppsrrd1/REDs/para-dichlorobenzene-red-revised.pdf |title= Reregistration Eligibility Decision for Para-dichlorobenzene |date= December 2008 |accessdate= 2009-08-10 }}</ref> The US [[Occupational Safety and Health Administration]] (OSHA) has set a maximum level of 75 parts of ''p''-DCB per million parts air in the workplace (75&nbsp;ppm) for an 8-hour day, 40-hour [[workweek]].{{Citation needed|date=June 2008}}

Little information is available on how children react to ''p''-DCB exposure; however, consumption of ''p''-DCB can cause vomiting in adults.<ref>[http://www.japantoday.com/category/national/view/woman-becomes-sick-after-eating-cup-noodle-chemical-found-in-soup Woman Sickened by Chemical-Tainted Cup Noodle], ''Japan Today''</ref>

Under California's [[Proposition 65]], ''p''-DCB is listed as "known to the State to cause cancer".<ref>[http://www.oehha.org/prop65.html Proposition 65], Office of Environmental Health Hazard Assessment</ref>

== See also ==
* [[Camphor]]
* [[Dichlorobenzene]]

==References==
{{reflist}}

==External links==
*{{ICSC|0037|00}}
*[http://news.bbc.co.uk/2/hi/health/5219646.stm Mothball sniffing warning issued], ''BBC News'', 27 July 2006

{{DEFAULTSORT:Dichlorobenzene, 1,4-}}
[[Category:Organochlorides]]
[[Category:Organochloride insecticides]]
[[Category:IARC Group 2B carcinogens]]

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