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1,4-Dichlorobenzene

1,4-Dichlorobenzene
1,4-Dichlorobenzene
Ball-and-stick model of 1,4-dichlorobenzene
Names
Preferred IUPAC name
1,4-Dichlorobenzene
Other names
para-Dichlorobenzene
p-Dichlorobenzene
p-DCB
PDB
Paramoth
Para crystals
Paracide
Dichlorocide
Identifiers
106-46-7 YesY
3D model (Jmol) Interactive image
ChEBI CHEBI:28618 N
ChEMBL ChEMBL190982 N
ChemSpider 13866817 N
ECHA InfoCard 100.003.092
KEGG C07092 YesY
RTECS number CZ4550000
UNII D149TYB5MK YesY
Properties
C6H4Cl2
Molar mass 147.00 g·mol−1
Appearance Colorless/white crystals
Odor mothball-like
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)
-82.93·10−6 cm3/mol
Hazards
Main hazards Suspected carcinogen
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
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 code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point 66 °C (151 °F; 339 K)
Explosive limits 2.5%-?
Lethal dose or concentration (LD, LC):
LD50 (median dose)
 500 mg/kg (oral, rat)
2950 mg/kg (oral, mouse)
2512 mg/kg (oral, rat)
2830 mg/kg (oral, rabbit)
857 mg/kg (human, oral)
4000 mg/kg (rat, oral)
2800 mg/kg (guinea pig, oral)
US health exposure limits (NIOSH):
PEL (Permissible)
 TWA 75 ppm (450 mg/m3)
REL (Recommended)
 Ca
IDLH (Immediate danger)
 Ca [150 ppm]
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).
N  (what is YesYN ?)
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. 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 pesticide and a 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 polymer poly(p-phenylene sulfide).

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

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.

p-DCB is used to control moths, molds, and mildew. It also finds use as a disinfectant 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.


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