1,2-Dichloroethylene

1,2-Dichloroethylene or 1,2-DCE is the name for a pair of organochlorine compounds with the molecular formula C₂H₂Cl₂. The two compounds are isomers, each being colorless liquids with a sweet odor. It can exist as either of two geometric isomers, cis-1,2-dichloroethene or trans-1,2-dichloroethene, but is often used as a mixture of the two. They have modest solubility in water. These compounds have some applications as a degreasing solvent.^[1] In contrast to most cis-trans compounds, the Z isomer (cis) is more stable than the E isomer (trans) by 0.4 kcal/mol.^[4]

1,2-Dichloroethylene

Skeletal formula of cis-1,2-dichloroethene Skeletal formula of trans-1,2-dichloroethene
Ball-and-stick model of cis-1,2-dichloroethene cis-1,2-Dichloroethene (Z) Ball-and-stick model of trans-1,2-dichloroethene trans-1,2-Dichloroethene (E)
Names
Preferred IUPAC name 1,2-Dichloroethene
Other names 1,2-Dichloroethene 1,2-DCE Acetylene dichloride sym-Dichloroethylene
Identifiers
CAS Number	156-59-2 (Z) Y 156-60-5 (E) Y 540-59-0 (E/Z) Y
3D model (JSmol)	Interactive image Interactive image
ChEBI	CHEBI:18882 Y
ChemSpider	10438 Y
ECHA InfoCard	100.007.956
EC Number	208-750-2
KEGG	C06792 Y
PubChem CID	643833 (Z) 638186 (E) 10900 (E/Z)
UNII	FYO9G15JYD (Z) Y 41799BI61U (E) Y XU9RUA6YUT (E/Z) Y
CompTox Dashboard (EPA)	DTXSID8024991
InChI InChI=1S/C2H2Cl2/c3-1-2-4/h1-2H Y Key: KFUSEUYYWQURPO-UHFFFAOYSA-N Y InChI=1/C2H2Cl2/c3-1-2-4/h1-2H/b2-1- Key: KFUSEUYYWQURPO-UPHRSURJBI InChI=1/C2H2Cl2/c3-1-2-4/h1-2H Key: KFUSEUYYWQURPO-UHFFFAOYAW
SMILES Cl[C@H]=CCl ClC=CCl
Properties
Chemical formula	C2H2Cl2
Molar mass	96.95 g/mol
Appearance	colorless liquid
Odor	sweet[1]
Density	Z: 1.28 g/cm3 E: 1.26 g/cm3
Melting point	Z: −81.47 °C E: −49.44 °C
Boiling point	Z: 60.2 °C E: 48.5 °C
Magnetic susceptibility (χ)	−51.0·10−6 cm3/mol (cis) −48.9·10−6 cm3/mol (trans)
Dipole moment	Z: 1.9 D E: 0 D
Hazards
Flash point	2–4 °C; 36–39 °F; 275–277 K
Explosive limits	5.6–12.8%[2]
Lethal dose or concentration (LD, LC):
LD50 (median dose)	770 mg/kg (oral, rat) 1275 mg/kg (oral, rat, trans-isomer)[3]
LC50 (median concentration)	21,273 ppm (mouse, 6 hr, trans-isomer)[3]
LCLo (lowest published)	16,000 ppm (rat, 6 hr, cis-isomer)[3]
NIOSH (US health exposure limits):
PEL (Permissible)	TWA 200 ppm (790 mg/m3)[2]
REL (Recommended)	TWA 200 ppm (790 mg/m3)[2]
IDLH (Immediate danger)	1000 ppm[2]
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

Production, uses and reactions

cis-DCE, the Z isomer, is obtainable by the controlled chlorination of acetylene:

C₂H₂ + Cl₂ → C₂H₂Cl₂

Industrially both isomers arise as byproducts of the production of vinyl chloride, which is produced on a vast scale. Unlike 1,1-dichloroethylene, the 1,2-dichloroethylene isomers do not polymerize.^[1]

trans-1,2-DCE has applications including electronics cleaning, precision cleaning, and certain metal cleaning applications.^[5]

Both isomers participate in Kumada coupling reactions. trans-1,2-Dichloroethylene participates in cycloaddition reactions.^[6]

Safety and environmental concerns

These compounds have "moderate oral toxicity to rats".^[1]

The dichloroethylene isomers occur in some polluted waters and soils, as the decomposition products of trichloroethylene. Significant attention has been paid to their further degradation, e.g. by iron particles.^[7][8]

See also

• 1,1-Dichloroethene
• 1,2-Dichloroethane, which is also often abbreviated as 1,2-DCE