CID 6344

CH₂Cl₂

Dichloromethane

C 1
H 2
Cl 2

Ball-and-stick Stick Space-filling

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5 atoms, 4 single bonds, tetrahedral.

IUPAC name: dichloromethane
Molar mass: 84.927(22) g/mol
Atoms: 5
Shape: tetrahedral
SMILES: C(Cl)Cl
InChIKey: YMWUJEATGCHHMB-UHFFFAOYSA-N
PubChem CID: 6344

Made of

C H Cl

Structural formula of dichloromethane. Each unlabelled corner is a carbon atom, and the two hydrogens on carbon are not drawn. It shows which atoms are joined to which, not the shape. The model above shows the shape.

In US regulation it goes by methylene chloride, but its systematic name, dichloromethane, describes the molecule exactly. ChEBI, the Chemical Entities of Biological Interest database, files it among the chloromethanes: methane with two of its four hydrogen atoms exchanged for chlorine. The International Chemical Safety Cards (ICSC) describe a very volatile, colourless liquid, and HSDB, the Hazardous Substances Data Bank, gives its boiling point as 39.75 °C. Its sweet odour is likened to that of chloroform.

The liquid is heavy: at 20 °C its density is 1.3255 times water’s, on HSDB’s figure, and CAMEO Chemicals notes that it sinks in water. A litre of water dissolves 13,200 mg of it at 25 °C according to HSDB, ICSC rates the solubility as moderate, and ChEBI calls the two liquids immiscible. Alcohol and ether, by contrast, mix with it in any proportion.

Structure and bonding

Two chlorines and two hydrogens surround dichloromethane’s carbon at the corners of a tetrahedron. With all the carbon’s electron pairs shared and no lone pair left, the bond arrangement is the molecule’s shape, Chem1 explains. The article on molecular shapes uses this very molecule as evidence for that tetrahedron.

The model’s tetrahedron is not quite regular. In its computed geometry the chlorines open to 111.2° and the hydrogens to 109.7°. Its bonds differ more, 1.767 Å for C–Cl against 1.093 Å for C–H, and the Stick view shows two long rods and two stubs. In Space-filling, two large chlorine spheres crowd the carbon, the hydrogens small bumps opposite them.

Electronegativity, an atom’s hold on the electrons of a bond it shares, is 3.16 for chlorine and 2.55 for carbon. By Chem1’s rule the shared electrons shift towards chlorine, which predicts polar C–Cl bonds, though the viewer draws no charges. Kept dry at ordinary temperatures, it is relatively stable compared with carbon tetrachloride and chloroform, according to HSDB.

Where it turns up

Spray paints, car cleaners, and aerosol and pesticide products have contained it, reports ATSDR, the US Agency for Toxic Substances and Disease Registry, and photographic film is made with it. Aerosol hairsprays once used it to help the product out of the can. The US Food and Drug Administration judged that a significant cancer risk, on the evidence of mouse tumours, and banned it from cosmetics. None of it forms naturally, ATSDR holds, though LOTUS, a record of natural products, lists it from Garcinia mangostana and Biflustra perfragilis.

Because it evaporates readily, most of what is released ends up in the air. Sunlight and other chemicals there break it down, over 90 per cent of it to carbon dioxide, ATSDR reports. In 1987 it ranked sixth by detection frequency among organic contaminants in groundwater at hazardous-waste sites, according to the National Toxicology Program (NTP).

Why it matters

On HSDB’s account, most is made from methanol and hydrogen chloride, which give methyl chloride; chlorine then turns that into dichloromethane, with chloroform and carbon tetrachloride as coproducts. Because one plant can make more than one chlorinated hydrocarbon, its output can be shifted between them. Paint strippers and removers were its main use, according to the US Environmental Protection Agency (EPA), and other uses ranged from drug manufacture to metal cleaning and urethane foam. HSDB names it the preferred starting material for the hydrofluorocarbon HFC-32, and the NTP lists it as a low-pressure refrigerant.

In March 2019 the EPA banned its manufacture, import, processing and distribution for consumer paint and coating removal, citing acute fatalities from that use. An April 2024 rule under the Toxic Substances Control Act (TSCA) ended all consumer uses and most industrial and commercial ones, paint removal included. Production of separators for electric-vehicle batteries continues, as do laboratory use and plastic and rubber manufacture, polycarbonate production among it. The European Union lists it as a restricted substance.

Properties

Properties of dichloromethane Molar mass summed from IUPAC/CIAAW 2024 standard atomic weights; formula, atom and bond counts and PubChem's molecular weight from PubChem CID 6344.
Property	Value	Unit	Source
Molecular formula (Hill order)	CH₂Cl₂
Molar mass	84.927(22) g/mol	g/mol	IUPAC/CIAAW 2024
Carbon atoms	1
Hydrogen atoms	2
Chlorine atoms	2
Bonds	4
PubChem molecular weight	84.93 g/mol	g/mol	PubChem

Safety

Dichloromethane is suspected of causing cancer under EU classification, and NIOSH, the US National Institute for Occupational Safety and Health, treats it as a potential occupational carcinogen. NIOSH lists the eyes, skin, cardiovascular system and central nervous system as its targets, and ICSC warns that exposure could cause carbon monoxide poisoning. Strong heat breaks it down into highly toxic phosgene and hydrogen chloride fumes. The PubChem Laboratory Chemical Safety Summary and the NIOSH card for methylene chloride set out the hazards and workplace limits.

Questions

Is dichloromethane tetrahedral?

Yes, built round a single carbon atom. That carbon holds two chlorine atoms and two hydrogen atoms by single bonds and keeps no lone pair. With four bonding partners and nothing else round the centre, the bond arrangement and the molecular shape coincide, on Chem1's account. The 3D model draws atoms and bonds only, and its computed geometry is a little uneven: 111.2° between the chlorines against 109.7° between the hydrogens.

Is dichloromethane used to decaffeinate coffee?

It has been used to strip caffeine from coffee and, according to ChEBI, from tea. US Food and Drug Administration rules permit it as an extraction solvent for coffee, hop extract and spice extracts, within prescribed limitations. Most decaffeinators no longer use it, according to the US Environmental Protection Agency, and the National Toxicology Program reports that health concerns have sharply reduced its use as an extraction solvent in food and coffee.

Does dichloromethane cause cancer?

In mice it causes lung and liver tumours. The International Agency for Research on Cancer placed it in Group 2A, probable human carcinogens, in 2014, and the National Toxicology Program reasonably anticipates it to be a human carcinogen. Whether it causes cancer in people is not known, says the US Agency for Toxic Substances and Disease Registry. One study in the Hazardous Substances Data Bank traces the mouse tumours to an enzyme route more active in mice; another doubts it.

What happens to dichloromethane in the body?

Most of it travels to the liver, kidneys, brain, lungs and fat, according to the US Agency for Toxic Substances and Disease Registry. Part is broken down to formic acid and to carbon monoxide, a gas the body also makes when it breaks down haemoglobin. Changed or unchanged, it leaves mainly in exhaled breath and stays in the blood only briefly. Dichloromethane itself also lowers haemoglobin's affinity for oxygen, according to the Hazardous Substances Data Bank.

Made of the same elements

CHCl₃ Chloroform 5 atoms, 4 single bonds, tetrahedral.
C₂H₃Cl Vinyl chloride 6 atoms, 5 bonds.

Same shape (tetrahedral)

CCl₄ Carbon tetrachloride 5 atoms, 4 single bonds, tetrahedral.
CHCl₃ Chloroform 5 atoms, 4 single bonds, tetrahedral.
CCl₂F₂ Dichlorodifluoromethane 5 atoms, 4 single bonds, tetrahedral.
CH₄ Methane 5 atoms, 4 single bonds, tetrahedral.
H₂SO₄ Sulfuric acid 7 atoms, 6 bonds, tetrahedral.