1,1,1-Trichloroethane

1,1,1-Trichloroethane

Skeletal formula of 1,1,1-trichloroethane Space-filling model of 1,1,1-trichloroethane
Names
Preferred IUPAC name 1,1,1-Trichloroethane
Other names 1,1,1-TCA, Methyl chloroform, Chlorothene, Solvent 111, R-140a, Genklene, monochlorethylidene chloride (archaic)
Identifiers
CAS Number	71-55-6 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:36015 Y
ChEMBL	ChEMBL16080 Y
ChemSpider	6042 Y
ECHA InfoCard	100.000.688
EC Number	200-756-3
Gmelin Reference	82076
IUPHAR/BPS	5482
KEGG	C18246 Y
PubChem CID	6278
RTECS number	KJ2975000
UNII	113C650IR1 Y
UN number	2831
CompTox Dashboard (EPA)	DTXSID0021381
InChI InChI=1S/C2H3Cl3/c1-2(3,4)5/h1H3 Y Key: UOCLXMDMGBRAIB-UHFFFAOYSA-N Y InChI=1/C2H3Cl3/c1-2(3,4)5/h1H3 Key: UOCLXMDMGBRAIB-UHFFFAOYAP
SMILES ClC(Cl)(Cl)C
Properties
Chemical formula	C2H3Cl3 or CH3CCl3
Molar mass	133.40 g/mol
Appearance	Colourless liquid
Odor	mild, chloroform-like
Density	1.32 g/cm3
Melting point	−33 °C (−27 °F; 240 K)
Boiling point	74 °C (165 °F; 347 K)
Solubility in water	0.4% (20°C) 0.480 g/litre at 20 °C
Vapor pressure	100 mmHg (20°C)
Refractive index (nD)	1.437
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	Ozone layer impact. Irritant to the upper respiratory tract. Causes severe irritation and swelling to eyes.
GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H332, H420
Precautionary statements	P261, P271, P304+P312, P304+P340, P312, P502
NFPA 704 (fire diamond)	2 1 0
Explosive limits	7.5%-12.5%
Lethal dose or concentration (LD, LC):
LD50 (median dose)	9600 mg/kg (oral, rat) 6000 mg/kg (oral, mouse) 5660 mg/kg (oral, rabbit)
LC50 (median concentration)	3911 ppm (mouse, 2 hr) 18000 ppm (rat, 4 hr)
NIOSH (US health exposure limits):
PEL (Permissible)	TWA 350 ppm (1900 mg/m3)
REL (Recommended)	C 350 ppm (1900 mg/m3) [15-minute]
IDLH (Immediate danger)	700 ppm
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

The organic compound 1,1,1-trichloroethane, also known as methyl chloroform and chlorothene, is a chloroalkane with the chemical formula CH₃CCl₃. It is an isomer of 1,1,2-trichloroethane. A colourless and sweet-smelling liquid, it was once produced industrially in large quantities for use as a solvent. It is regulated by the Montreal Protocol as an ozone-depleting substance and as such use has declined since 1996. Trichloroethane should not be confused with the similar-sounding trichloroethene which is also commonly used as a solvent.

Production

1,1,1-Trichloroethane was first reported by Henri Victor Regnault in 1840. Industrially, it is usually produced in a two-step process from vinyl chloride. In the first step, vinyl chloride reacts with hydrogen chloride at 20-50 °C to produce 1,1-dichloroethane:

CH₂=CHCl + HCl → CH₃CHCl₂

This reaction is catalyzed by a variety of Lewis acids, mainly aluminium chloride, iron(III) chloride, or zinc chloride. The 1,1-dichloroethane is then converted to 1,1,1-trichloroethane by reaction with chlorine under ultraviolet irradiation:

CH₃CHCl₂ + Cl₂ → CH₃CCl₃ + HCl

This reaction proceeds at 80-90% yield, and the hydrogen chloride byproduct can be recycled to the first step in the process. The major side-product is the related compound 1,1,2-trichloroethane, from which the 1,1,1-trichloroethane can be separated by distillation.

A somewhat smaller amount of 1,1,1-trichloroethane is produced from the reaction of 1,1-dichloroethene and hydrogen chloride in the presence of an iron(III) chloride catalyst:

CH₂=CCl₂ + HCl → CH₃CCl₃

1,1,1-Trichloroethane is sold with stabilizers because it is unstable with respect to dehydrochlorination and attacks some metals. Stabilizers comprise up to 8% of the formulation, including acid scavengers (epoxides, amines) and complexants.

Uses

1,1,1-Trichloroethane is an excellent solvent for many organic compounds and also one of the least toxic of the chlorinated hydrocarbons. It is generally considered non-polar, but owing to the good polarizability of the chlorine atoms, it is a superior solvent for organic compounds that do not dissolve well in hydrocarbons such as hexane. Prior to the Montreal Protocol, it was widely used for cleaning metal parts and circuit boards, as a photoresist solvent in the electronics industry, as an aerosol propellant, as a cutting fluid additive, and as a solvent for inks, paints, adhesives, and other coatings. 1,1,1-Trichloroethane was used to dry-clean leather and suede. 1,1,1-Trichloroethane is also used as an insecticidal fumigant.

It was also the standard cleaner for photographic film (movie/slide/negatives, etc.). Other commonly available solvents damage emulsion and base (acetone will severely damage triacetate base on most films), and thus are not suitable for this application. The standard replacement, Forane 141 is much less effective, and tends to leave a residue. 1,1,1-Trichloroethane was used as a thinner in correction fluid products such as liquid paper. Many of its applications previously used carbon tetrachloride (which was banned in US consumer products in 1970). In turn, 1,1,1-trichloroethane itself is now being replaced by other solvents in the laboratory.

Anaesthetic research

1,1,1-Trichloroethane was one of the volatile organochlorides that have been tried as alternatives to chloroform in anaesthesia. In the 1880s, it was found to be a safe and strong substitute for chloroform but its production was too expensive and difficult for the era.

In 1880, 1,1,1-Trichloroethane was suggested as an anaesthetic. It was first referred to as "methyl-chloroform" in the same year. At the time, the narcotic effects of chloral hydrate were owed to a hypothetical metabolic pathway to chloroform in "alkaline blood". Trichloroethane was studied for its structural similarity to chloral and potential anaesthetic effects. However, trichloroethane did not exhibit any conversion to chloroform in laboratory experiments. The 1,1,2-trichloroethane isomer, which lacked a trichloromethyl group, exhibited anaesthetic effects even stronger than the 1,1,1 isomer.

Safety

Although not as toxic as many similar compounds, inhaled or ingested 1,1,1-trichloroethane does act as a central nervous system depressant and can cause effects similar to those of ethanol intoxication, including dizziness, confusion, and, in sufficiently high concentrations, unconsciousness and death. Fatal poisonings and illnesses linked to intentional inhalation of trichloroethane have been reported.

Prolonged skin contact with the liquid can result in the removal of fats from the skin, resulting in skin irritation.

The International Agency for Research on Cancer places 1,1,1-trichloroethane in Group 2A as a probable carcinogen.

Atmospheric concentration

1,1,1-Trichloroethane (Methyl chloroform, CH₃CCl₃) measured by the Advanced Global Atmospheric Gases Experiment (AGAGE) in the lower atmosphere (troposphere) at stations around the world. Abundances are given as pollution free monthly mean mole fractions in parts-per-trillion.

1,1,1-Trichloroethane timeseries at various latitudes.

1,1,1-Trichloroethane is a fairly potent greenhouse gas with a 100-year global warming potential of 169 relative to carbon dioxide. This is nonetheless less than a tenth that of carbon tetrachloride — which it replaced as a solvent — due to its relatively short atmospheric lifetime of about 5 years.

The Montreal Protocol targeted 1,1,1-trichloroethane as a compound responsible for ozone depletion and banned its use beginning in 1996. Since then, its manufacture and use have been phased out throughout most of the world, and its atmospheric concentration has declined substantially.

Further reading

• Doherty, R.E. (2000). "A History of the Production and Use of Carbon Tetrachloride, Tetrachloroethylene, Trichloroethylene and 1,1,1-Trichloroethane in the United States: Part 2 - Trichloroethylene and 1,1,1-Trichloroethane". Environmental Forensics. 1 (2): 83–93. Bibcode:2000EnvFo...1...83D. doi:10.1006/enfo.2000.0011. S2CID 97370778.