1,2-Dichlorobenzene

1,2-Dichlorobenzene, or orthodichlorobenzene (ODCB), is an aryl chloride and isomer of dichlorobenzene with the formula C₆H₄Cl₂. This colourless liquid is poorly soluble in water but miscible with most organic solvents. It is a derivative of benzene, consisting of two adjacent chlorine atoms.

1,2-Dichlorobenzene^[1]

Skeletal structure of 1,2-Dichlorobenzene
Ball-and-stick model of the 1,2-dichlorobenzene molecule Space-filling model of the 1,2-dichlorobenzene molecule
Names
Preferred IUPAC name 1,2-Dichlorobenzene
Other names ortho-Dichlorobenzene, o-Dichlorobenzene, odcb, o-Dichlorobenzol
Identifiers
CAS Number	95-50-1 Y
3D model (JSmol)	Interactive image Interactive image
ChEBI	CHEBI:35290 Y
ChEMBL	ChEMBL298461 Y
ChemSpider	13837988 Y
ECHA InfoCard	100.002.206
EC Number	202-425-9
KEGG	C14328 Y
PubChem CID	7239
UNII	6PJ93I88XL Y
CompTox Dashboard (EPA)	DTXSID6020430
InChI InChI=1S/C6H4Cl2/c7-5-3-1-2-4-6(5)8/h1-4H Y Key: RFFLAFLAYFXFSW-UHFFFAOYSA-N Y InChI=1/C6H4Cl2/c7-5-3-1-2-4-6(5)8/h1-4H Key: RFFLAFLAYFXFSW-UHFFFAOYAE
SMILES c1ccc(c(c1)Cl)Cl c1ccc(c(c1)Cl)Cl
Properties
Chemical formula	C6H4Cl2
Molar mass	147.01 g/mol
Appearance	colourless liquid
Odor	Naphthalene-like
Density	1.30 g/cm3
Melting point	−17.03 °C (1.35 °F; 256.12 K)
Boiling point	180.19 °C (356.34 °F; 453.34 K)[2]
Solubility in water	0.01%[3]
Vapor pressure	1 mmHg (20°C)
Magnetic susceptibility (χ)	−84.26·10−6 cm3/mol
Refractive index (nD)	1.54920
Viscosity	1.0656 (20 °C)
Hazards
Occupational safety and health (OHS/OSH):
Ingestion hazards	Mildly toxic
Inhalation hazards	Causes respiratory tract irritation
Eye hazards	Causes eye irritation
Skin hazards	Causes skin irritation
Flash point	66 °C (151 °F; 339 K)
Explosive limits	2.2%–9.2%[3]
Lethal dose or concentration (LD, LC):
LD50 (median dose)	500 mg/kg (oral, rat, rabbit) 200 mg/kg (oral, guinea pig) 436 mg/kg (oral, mouse)[4]
LCLo (lowest published)	1000 ppm (guinea pig, 20 hr) 800 ppm (guinea pig, 24 hr) 821 ppm (rat, 7 hr)[4]
NIOSH (US health exposure limits):
PEL (Permissible)	C 50 ppm (300 mg/m3)[3]
REL (Recommended)	C 50 ppm (300 mg/m3)[3]
IDLH (Immediate danger)	200 ppm[3]
Safety data sheet (SDS)	External MSDS
Related compounds
Related compounds	1,2-Difluorobenzene 1,2-Dibromobenzene
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

It is mainly used as a precursor chemical in the synthesis of agrochemicals, as a preferred solvent for dissolving and working with fullerenes, as an insecticide, and in softening and removing carbon-based contamination on metal surfaces.

Production and uses

1,2-Dichlorobenzene is obtained as a side-product of the production of chlorobenzene:

C
₆H
₅Cl + Cl
₂ → C
₆H
₄Cl
₂ + HCl

The reaction also affords the 1,4- and small amounts of the 1,3-isomer. The 1,4- isomer is preferred over the 1,2- isomer due to steric hindrance. The 1,3- isomer is uncommon because it is a meta- compound, while chlorine, like all halogens, is an ortho/para- director in terms of electrophilic aromatic substitution.

It is mainly used as a precursor to 1,2-dichloro-4-nitrobenzene, an intermediate in the synthesis of agrochemicals.^[5] In terms of niche applications, 1,2-dichlorobenzene is a versatile, high-boiling solvent. It is a preferred solvent for dissolving and working with fullerenes. It is an insecticide for termites and locust borers, historically used by the United States Forest Service to combat widespread bark beetle outbreaks.^[6]

1,2-Dichlorobenzene is also used in softening and removing carbon-based contamination on metal surfaces.^[7]

Safety

Data from human exposure to 1,2-dichlorobenzene shows that concentrations of 100 ppm have been reported to cause sporadic irritation of the eyes and respiratory tract.^[8] The Occupational Safety and Health Administration and the National Institute for Occupational Safety and Health have set occupational exposure limits at a ceiling of 50 ppm, over an eight-hour workday.^[9]

See also

• Chlorobenzenes—different numbers of chlorine substituents and isomeric forms