1,1,1-Trichloroethane

1,1,1-Trichloroethane
Skeletal formula of 1,1,1-trichloroethane	Space-filling model of 1,1,1-trichloroethane
IUPAC name 1,1,1-trichloroethane
Other names methyl chloroform, chlorothene, Solvent 111, Genklene
style="background: #F8EABA; text-align: center;" colspan="2" | Identifiers
CAS number	71-55-6 Y
SMILES
style="background: #F8EABA; text-align: center;" colspan="2" | Properties
Molecular formula	C2H3Cl3 or CH3CCl3
Molar mass	133.40 g/mol
Appearance	Colorless liquid
Density	1.32 g/cm3
Melting point	-33 °C, 240 K, -27 °F
Boiling point	74 °C, 347 K, 165 °F
Solubility in water	insoluble in water
style="background: #F8EABA; text-align: center;" colspan="2" | Hazards
R-phrases	R19 R20 R40 R59 R66
S-phrases	S9 S16 S24 S25 S46 S59 S61
NFPA 704	75px 1 3 1
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

The organic compound 1,1,1-trichloroethane is a chloroalkane. This colourless, sweet-smelling liquid was produced industrially in large quantities for use as a solvent. It is regulated by the Montreal Protocol as an ozone depleting substance and its use is being rapidly phased out.

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 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 vinylidene chloride and hydrogen chloride in the presence of an iron(III) chloride catalyst:

CH₂=CCl₂ + HCl → CH₃CCl₃

1,1,1-Trichloroethane is marketed with stabilizers since the pure liquid is unstable with respect to dehydrochlorination and attacks some metals. Stabilizers comprise up to 8% of the formulation, include acid accepts (epoxides, amines) and complexants.

Uses

1,1,1-Trichloroethane is an excellent solvent for many organic materials and also one of the least toxic of the chlorinated hydrocarbons. 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.

It was also the standard cleaner for photographic film (movie/slide/negatives, etc.). Other commonly available solvents damage emulsion, 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 applications for 1,1,1-trichloroethane (including film cleaning) were previously done with carbon tetrachloride, which was banned in 1970.

The Montreal Protocol targeted 1,1,1-trichloroethane as one of those compounds responsible for ozone depletion and banned its use beginning in 1996. Since then, its manufacture and use has been phased out throughout most of the world.

1,1,1-Trichloroethane is generally considered as a non-polar solvent, but since all three electronegative chlorine atoms lie on the same side of the molecule, it is slightly polar, making it a good solvent for organic matters that do not dissolve into totally non-polar substances such as hexane. 1,1,1-Trichloroethane in laboratory analytics has been replaced by other solvents.

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 intoxication, including dizziness, confusion, and in sufficiently high concentrations, unconsciousness and death.

Fatal poisonings have been reported. and illness linked to trichloroethane from intentional inhalation in the 1980s. The removal of the chemical from correction fluid commenced due to Proposition 65 declaring it hazardous and toxic

Prolonged skin contact with the liquid can result in the removal of fats from the skin, resulting in chronic skin irritation. Studies on laboratory animals have shown that 1,1,1-trichloroethane is not retained in the body for long periods of time. However, chronic exposure has been linked to abnormalities in the liver, kidneys, and heart. Pregnant women should avoid exposure, as the compound has been linked to birth defects in laboratory animals (see teratogenesis).

The substance is deadly to insects.

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, Journal of Environmental Forensics (2000) 1, 83-93.de:1,1,1-Trichlorethan

zh:1,1,1-三氯乙烷