1,4-Dichlorobenzene

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1,4-Dichlorobenzene
1,4-Dichlorobenzene Ball-and-stick model of 1,4-dichlorobenzene
Identifiers
CAS number 106-46-7 YesY
ChemSpider 13866817 N
UNII D149TYB5MK YesY
KEGG C07092 YesY
ChEBI CHEBI:28618 N
ChEMBL CHEMBL190982 N
RTECS number CZ4550000
Jmol-3D images Image 1
Properties
Molecular formula C6H4Cl2
Molar mass 147.00 g mol−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)
Solubility in water 10.5 mg/100 mL (20 °C)
Hazards
EU classification Harmful Xn
Dangerous for the Environment (Nature) N
Carc. Cat. 3
R-phrases R36 R40 R50/53
S-phrases (S2) S36/37 S46 S60 S61
Main hazards Suspected carcinogen
NFPA 704
Flammability code 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 fuel Health code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroform Reactivity (yellow): no hazard code Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point 66 °C (151 °F; 339 K)
Related compounds
Related compounds 1,2-Dichlorobenzene
1,3-Dichlorobenzene
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N (verify) (what is: YesY/N?)
Infobox references

1,4-Dichlorobenzene (p-DCB or para-dichlorobenzene, sometimes abbreviated as PDB or para) is an organic compound with the formula C6H4Cl2. This colorless solid has a strong odor. In terms of its structure, the molecule consists of two chlorine atoms substituted for hydrogen at opposing sites on a benzene ring. p-DCB is used as a pesticide and a deodorant, most familiarly in mothballs in which it is a replacement for the more traditional naphthalene. p-DCB is also used as a precursor in the production of the polymer poly(p-phenylene sulfide).[1]

Production[edit]

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 crystallisation, taking advantage of its relatively high melting point of 53.5 °C; the isomeric dichlorobenzenes and chlorobenzene melt well below room temperature.[1]

Uses[edit]

Disinfectant, deodorant, and pesticide[edit]

p-DCB is used to control moths, moulds, and mildew.[2] It also finds use as a disinfectant[1] 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.[1]

Precursor to other chemicals[edit]

The chloride centres 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):[3]

Synthesis of Polyphenylensulfide

Environmental and health effects[edit]

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.

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.[4] This has been indicated by animal studies, although a full-scale human study has not been done.[5] Animals given very high levels in water developed liver and kidney tumors.[citation needed]

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).[6] p-DCB is also an EPA-registered pesticide.[7] 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.[citation needed]

Under California's Proposition 65, p-DCB is listed as "known to the State to cause cancer".[8] A probable mechanism for the carcinogenic effects of mothballs and some types of air fresheners containing p-DCB has been identified.[9][10]

See also[edit]

References[edit]

  1. ^ a b c d 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. doi:10.1002/14356007.a06_233.pub2. ISBN 3527306730. 
  2. ^ "National Pesticide Information Center – Mothballs Case Profile". Retrieved 10 August 2009. 
  3. ^ Fahey, D. R.; Ash, C. E. (1991). "Mechanism of poly(p-phenylene sulfide) growth from p-dichlorobenzene and sodium sulfide". Macromolecules 24 (15): 4242. doi:10.1021/ma00015a003. 
  4. ^ Preamble to the IARC Monographs definition of "Group 2B: Possibly carcinogenic to humans", the International Agency for Research on Cancer classification of this chemical
  5. ^ "ToxFAQs™ for Dichlorobenzenes". Toxic Substances Portal. Agency for Toxic Substances and Disease Registry. Retrieved 24 May 2013. 
  6. ^ "Consumer Factsheet on: PARA-DICHLOROBENZENE (p-DCB)". 28 November 2006. Archived from the original on 6 October 2009. Retrieved 10 August 2009. 
  7. ^ "Reregistration Eligibility Decision for Para-dichlorobenzene". December 2008. Archived from the original on 26 September 2009. Retrieved 10 August 2009. 
  8. ^ Proposition 65, Office of Environmental Health Hazard Assessment
  9. ^ "Scientists May Have Solved Mystery Of Carcinogenic Mothballs", Physorg.com, 20 June 2006.
  10. ^ "Mothballs, air fresheners and cancer". Environmental Health Association of Nova Scotia. Environmental Health Association of Nova Scotia. Retrieved 24 May 2013. 

External links[edit]