1,4-Dichlorobenzene

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1,4-Dichlorobenzene
1,4-Dichlorobenzene 1,4-dichlorobenzene.svg
1,4-Dichlorobenzene
Ball-and-stick model of 1,4-dichlorobenzene P-Dichlorobenzene-3D-balls.png
Ball-and-stick model of 1,4-dichlorobenzene
1,4 dichlorobenzene crystallised.jpg
1,4-dichlorobenzene crystallised on paper from DCM solution
Names
Preferred IUPAC name
1,4-Dichlorobenzene
Other names
1,4-DCB
para-Dichlorobenzene
p-Dichlorobenzene
p-DCB
PDCB
Paramoth
Para crystals
Paracide
Dichlorocide
Identifiers
3D model (JSmol)
1680023
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.003.092 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 203-400-5
49722
KEGG
PubChem CID
RTECS number
  • CZ4550000
UNII
UN number 3077
  • InChI=1S/C6H4Cl2/c7-5-1-2-6(8)4-3-5/h1-4H X mark.svgN
    Key: OCJBOOLMMGQPQU-UHFFFAOYSA-N X mark.svgN
  • ClC1=CC=C(Cl)C=C1
Properties
C6H4Cl2
Molar mass 147.00 g·mol−1
AppearanceColorless/white crystals [1]
Odor mothball-like [1]
Density 1.25 g/cm3, solid
Melting point 53.5 °C (128.3 °F; 326.6 K)
Boiling point 174 °C (345 °F; 447 K)
10.5 mg/100 mL (20 °C)
Vapor pressure 1.3 mmHg (20 °C) [1]
−82.93·10−6 cm3/mol
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
Suspected carcinogen
GHS labelling:
GHS-pictogram-exclam.svg GHS-pictogram-silhouette.svg GHS-pictogram-pollu.svg
Warning
H302, H315, H317, H319, H332, H335, H351, H410
P201, P202, P261, P264, P270, P271, P272, P273, P280, P281, P301+P312, P302+P352, P304+P312, P304+P340, P305+P351+P338, P308+P313, P312, P321, P330, P332+P313, P333+P313, P337+P313, P362, P363, P391, P403+P233, P405, P501
NFPA 704 (fire diamond)
NFPA 704.svgHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 2: Must be moderately heated or exposed to relatively high ambient temperature before ignition can occur. Flash point between 38 and 93 °C (100 and 200 °F). E.g. diesel fuelInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
2
2
0
Flash point 66 °C (151 °F; 339 K)
Explosive limits 2.5%-? [1]
Lethal dose or concentration (LD, LC):
500 mg/kg (rat, oral)
2950 mg/kg (mouse, oral)
2512 mg/kg (rat, oral)
2830 mg/kg (rabbit, oral) [2]
857 mg/kg (human, oral)
4000 mg/kg (rat, oral)
2800 mg/kg (guinea pig, oral) [2]
NIOSH (US health exposure limits):
PEL (Permissible)
TWA 75 ppm (450 mg/m3) [1]
REL (Recommended)
Ca [1]
IDLH (Immediate danger)
Ca [150 ppm] [1]
Related compounds
Related compounds
 1,2-Dichlorobenzene
1,3-Dichlorobenzene
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

1,4-Dichlorobenzene (1,4-DCB, p-DCB, or para-dichlorobenzene, sometimes abbreviated as PDCB or para) is an aryl chloride and isomer of dichlorobenzene with the formula C6H4Cl2. This colorless solid has a strong odor. The molecule consists of a benzene ring with two chlorine atoms (replacing hydrogen atoms) on opposing sites of the ring.

It is used as a disinfectant, pesticide, and deodorant, most familiarly in mothballs in which it is a replacement for the more traditional naphthalene because of naphthalene's greater flammability (though both chemicals have the same NFPA 704 rating). It is also used as a precursor in the production of the chemically and thermally resistant polymer poly(p-phenylene sulfide). [3]

Production

p-DCB is produced by chlorination of benzene using ferric chloride as a catalyst:

C6H6 + 2 Cl2 → C6H4Cl2 + 2 HCl

The chief impurity is the 1,2 isomer. The compound can be purified by fractional crystallization, taking advantage of its relatively high melting point of 53.5 °C; the isomeric dichlorobenzenes and chlorobenzene melt well below room temperature. [3]

Uses

Disinfectant, deodorant, and pesticide

1,4-dichlorobenzene balls sold as urinal disinfectant 1,4 dichlorobenzene balls.jpg
1,4-dichlorobenzene balls sold as urinal disinfectant

p-DCB is used to control moths, molds, and mildew. [4] It also finds use as a disinfectant [3] in waste containers and restrooms and is the characteristic smell associated with urinal cakes. Its usefulness for these applications arises from p-DCB's low solubility in water and its relatively high volatility: it sublimes readily near room temperature. [3]

Precursor to other chemicals

Nitration gives 1,4-dichloronitrobenzene, a precursor to commercial dyes and pigments. [5] The chloride sites on p-DCB can be substituted with hydroxylamine and sulfide groups. In a growing application, p-DCB is the precursor to the high performance polymer poly(p-phenylene sulfide): [6]

Synthesis Poly(p-phenylene sulfide).svg

As ceruminolytic agent

2% Paradichlorobenzene used as a ceruminolytic agent for the treatment of impacted wax. [7]

Environmental and health 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 fatty tissues if consumed by a person or animal.

The United States 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. [8] This has been indicated by animal studies, although a full-scale human study has not been done. [9]

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 μg/L), [10] but publishes no information on the cancer risk. [11] p-DCB is also an EPA-registered pesticide. [12] The United States 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 ppm) for an 8-hour day, 40-hour workweek. [13] [14]

A mechanism for the carcinogenic effects of mothballs and some types of air fresheners containing p-DCB has been identified in roundworms. [15]

Due to its carcinogenic nature, use of paradichlorobenzene in the European Union is forbidden as an air freshener (since 2005) and in mothballs (since 2008).

Biodegradation

Rhodococcus phenolicus is a bacterium species able to degrade dichlorobenzene as its sole carbon source. [16]

See also

References

  1. 1 2 3 4 5 6 7 NIOSH Pocket Guide to Chemical Hazards. "#0190". National Institute for Occupational Safety and Health (NIOSH).
  2. 1 2 "p-Dichlorobenzene". National Institute for Occupational Safety and Health (NIOSH). 4 December 2014. Retrieved 6 March 2015.
  3. 1 2 3 4 Rossberg, M.; Lendle, W.; Pfleiderer, G.; Tögel, A.; Dreher, E. L.; Langer, E.; Rassaerts, H.; Kleinschmidt, P.; Strack, H.; Cook, R.; Beck, U.; Lipper, K.-A.; Torkelson, T.R.; Löser, E.; Beutel, K.K.; Mann, T. (2006). "Chlorinated Hydrocarbons". Ullmann's Encyclopedia of Industrial Chemistry . Weinheim: Wiley-VCH. doi:10.1002/14356007.a06_233.pub2. ISBN   978-3-527-30673-2.
  4. ↑ "National Pesticide Information Center – Mothballs Case Profile" (PDF). Archived from the original (PDF) on 22 June 2010. Retrieved 10 August 2009.
  5. ↑ K. Hunger. W. Herbst "Pigments, Organic" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2012. doi : 10.1002/14356007.a20_371
  6. ↑ Fahey, D. R.; Ash, C. E. (1991). "Mechanism of poly(p-phenylene sulfide) growth from p-dichlorobenzene and sodium sulfide". Macromolecules. 24 (15): 4242. Bibcode:1991MaMol..24.4242F. doi:10.1021/ma00015a003.
  7. ↑ https://pmc.ncbi.nlm.nih.gov/articles/PMC3449978
  8. ↑ Preamble to the IARC Monographs Archived 9 August 2016 at the Wayback Machine definition of "Group 2B: Possibly carcinogenic to humans", the International Agency for Research on Cancer classification of this chemical
  9. ↑ "ToxFAQs for Dichlorobenzenes". Toxic Substances Portal. Agency for Toxic Substances and Disease Registry. Retrieved 24 May 2013.
  10. ↑ "Consumer Factsheet on: PARA-DICHLOROBENZENE (p-DCB)". 28 November 2006. Archived from the original on 6 October 2009. Retrieved 10 August 2009.
  11. ↑ "1,4-Dichlorobenzene (para-Dichlorobenzene)". US Environmental Protection Agency. Archived from the original on 4 April 2016. Retrieved 24 March 2016.
  12. ↑ "Reregistration Eligibility Decision for Para-dichlorobenzene" (PDF). December 2008. Archived from the original (PDF) on 26 September 2009. Retrieved 10 August 2009.
  13. ↑ "Chemical Sampling – p-Diclorobenzine". United States Department of Labor. Occupational Safety & Health Administration. Archived from the original on 31 July 2017. Retrieved 23 March 2016.
  14. ↑ "Common Name: 1,4-DICHLOROBENZENE" (PDF). New Jersey Department of Health and Senior Services. December 2005. Retrieved 24 March 2016.
  15. ↑ Kokel, David (14 May 2006). "The nongenotoxic carcinogens naphthalene and para-dichlorobenzene suppress apoptosis in Caenorhabditis elegans". Nature Chemical Biology. 2 (6): 338–345. doi:10.1038/nchembio791. PMID   16699520. S2CID   18402091.
  16. ↑ Rehfuss, M.; Urban, J. (2005). "Rhodococcus phenolicus sp. nov., a novel bioprocessor isolated actinomycete with the ability to degrade chlorobenzene, dichlorobenzene and phenol as sole carbon sources". Systematic and Applied Microbiology. 28 (8): 695–701. doi:10.1016/j.syapm.2005.05.011. PMID   16261859.
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