| |||
 1,4-dichlorobenzene crystallised on paper fromDCM 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 | ||
| EC Number |
| ||
| 49722 | |||
| KEGG |
| ||
| RTECS number |
| ||
| UNII | |||
| UN number | 3077 | ||
| |||
| |||
| Properties | |||
| C6H4Cl2 | |||
| Molar mass | 147.00 g·mol−1 | ||
| Appearance | Colorless/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 | Suspectedcarcinogen | ||
| GHS labelling: | |||
   | |||
| 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) | |||
| Flash point | 66 °C (151 °F; 339 K) | ||
| Explosive limits | 2.5%-?[1] | ||
| Lethal dose or concentration (LD, LC): | |||
LD50 (median dose) | 500 mg/kg (rat, oral) 2950 mg/kg (mouse, oral) 2512 mg/kg (rat, oral) 2830 mg/kg (rabbit, oral)[2] | ||
LDLo (lowest published) | 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 theirstandard state (at 25 °C [77 °F], 100 kPa). | |||
1,4-Dichlorobenzene (1,4-DCB,p-DCB, orpara-dichlorobenzene, sometimes abbreviated asPDCB orpara) is anaryl chloride and isomer ofdichlorobenzene with theformula C6H4Cl2. This colorless solid has a strongodor. The molecule consists of abenzene ring with twochlorine atoms (replacing hydrogen atoms) on opposing sites of the ring.
It is used as adisinfectant,pesticide, anddeodorant, most familiarly inmothballs in which it is a replacement for the more traditionalnaphthalene because of naphthalene's greaterflammability (though both chemicals have the sameNFPA 704 rating). It is also used as aprecursor in the production of the chemically and thermally resistant polymerpoly(p-phenylene sulfide).[3]
p-DCB is produced bychlorination of benzene usingferric chloride as a catalyst:
The chief impurity is the 1,2isomer. The compound can be purified byfractional crystallization, taking advantage of its relatively highmelting point of 53.5 °C; the isomericdichlorobenzenes andchlorobenzene melt well below room temperature.[3]
p-DCB is used to controlmoths,molds, andmildew.[4] It also finds use as a disinfectant[3] in waste containers and restrooms and is the characteristic smell associated withurinal cakes. Its usefulness for these applications arises fromp-DCB's lowsolubility in water and its relatively highvolatility: itsublimes readily near room temperature.[3]
Nitration gives1,4-dichloronitrobenzene, a precursor to commercialdyes and pigments.[5] The chloride sites onp-DCB can besubstituted with hydroxylamine and sulfide groups. In a growing application,p-DCB is the precursor to the high performance polymer poly(p-phenylene sulfide):[6]
.svg)
2% Paradichlorobenzene used as aceruminolytic agent for the treatment of impactedearwax.[7]
p-DCB is poorly soluble in water and is not easily broken down bysoil organisms. Like manyhydrocarbons,p-DCB islipophilic and will accumulate in fatty tissues if consumed by a person or animal.
The United StatesDepartment of Health and Human Services (DHHS) and theInternational Agency for Research on Cancer (IARC) have determined thatp-DCB may reasonably be anticipated to be acarcinogen.[8] This has been indicated by animal studies, although a full-scale human study has not been done.[9]
TheUnited States Environmental Protection Agency (EPA) has set a target maximumcontaminant level of 75micrograms ofp-DCB per liter ofdrinking water (75 μg/L),[10] but publishes no information on the cancer risk.[11]p-DCB is also anEPA-registeredpesticide.[12] The United StatesOccupational Safety and Health Administration (OSHA) has set a maximum level of 75 parts ofp-DCB per million parts air in the workplace (75 ppm) for an 8-hour day, 40-hourworkweek.[13][14]
A mechanism for the carcinogenic effects of mothballs and some types of air fresheners containingp-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).
Rhodococcus phenolicus is abacterium species able to degrade dichlorobenzene as its solecarbon source.[16]
