1,1,1-Trichloroethane

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Not to be confused with 1,1,1-Trifluoroethane.
1,1,1-Trichloroethane
Skeletal formula of 1,1,1-trichloroethane Space-filling model of 1,1,1-trichloroethane
Identifiers
CAS number 71-55-6 YesY
PubChem 6278
ChemSpider 6042 YesY
UNII 113C650IR1 YesY
KEGG C18246 YesY
ChEBI CHEBI:36015 YesY
ChEMBL CHEMBL16080 YesY
Jmol-3D images Image 1
Properties
Molecular formula C2H3Cl3 or CH3CCl3
Molar mass 133.40 g/mol
Appearance Colorless liquid
Density 1.32 g/cm3
Melting point −33 °C (−27 °F; 240 K)
Boiling point 74 °C (165 °F; 347 K)
Solubility in water insoluble in water
Hazards
R-phrases R19 R20 R40 R59 R66
S-phrases S9 S16 S24 S25 S46 S59 S61
Main hazards Irritant to the upper respiratory tract. Causes severe irritation and swelling to eyes.
NFPA 704
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g., canola oil Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g., calcium Special hazards (white): no codeNFPA 704 four-colored diamond
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 YesY (verify) (what is: YesY/N?)
Infobox references

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

Production[edit]

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 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 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. 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.

Uses[edit]

1,1,1-trichloroethane is generally considered a polar solvent. Owing to its asymmetrical structure, it is a superior solvent for organic compounds that do not dissolve well in hydrocarbons such as hexane. It 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. 1,1,1-trichloroethane is also used as an insecticidal fumigant.[2]

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 of its applications previously used carbon tetrachloride (which was banned in 1970). In turn, 1,1,1-trichloroethane itself is now being replaced by other solvents in the laboratory.[3]

Safety[edit]

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.[4] Fatal poisonings and illnesses linked to intentional inhalation of trichloroethane have been reported.[5][6][7][8] The removal of the chemical from correction fluid commenced due to Proposition 65 declaring it hazardous and toxic[9][10]

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).

References[edit]

  1. ^ Manfred Rossberg, Wilhelm Lendle, Gerhard Pfleiderer, Adolf Tögel, Eberhard-Ludwig Dreher, Ernst Langer, Heinz Rassaerts, Peter Kleinschmidt, Heinz Strack, Richard Cook, Uwe Beck, Karl-August Lipper, Theodore R. Torkelson, Eckhard Löser, Klaus K. Beutel, Trevor Mann “Chlorinated Hydrocarbons” in Ullmann's Encyclopedia of Industrial Chemistry 2006, Wiley-VCH, Weinheim. doi:10.1002/14356007.a06_233.pub2.
  2. ^ Methylchloroform data sheet, alanwood.net
  3. ^ Use of Ozone Depleting Substances in Laboratories. TemaNord 516/2003
  4. ^ Toxicological Profile for 1,1,1-Trichloroethane, Agency for Toxic Substances and Disease Registry (ATSDR). 2006
  5. ^ King, Gregory S.; Smialek, John E.; Troutman, William G. (15 March 1985). "Sudden Death in Adolescents Resulting From the Inhalation of Typewriter Correction Fluid". JAMA : the Journal of the American Medical Association 253 (11): 1604–1606. doi:10.1001/jama.253.11.1604. PMID 3974043. Archived from the original on 2009-07-25. Retrieved 2010-01-05. "We describe four cases of sudden death in adolescents associated with recreational sniffing of typewriter correction fluid occurring during the period 1979 through mid-1984." 
  6. ^ D'costa, DF; Gunasekera, NP (August 1990). "Fatal cerebral oedema following trichloroethane abuse". Journal of the Royal Society of Medicine 83 (8): 533–534. PMC 1292788. PMID 2231588. 
  7. ^ Winekab, Charles L.; Wahba, Wagdy W.; Huston, Robert; Rozin, Leon (6 June 1997). "Fatal inhalation of 1,1,1-trichloroethane". Forensic Science International 87 (2): 161–165. doi:10.1016/S0379-0738(97)00040-6. PMID 9237378. Archived from the original on 2009-07-25. Retrieved 2010-01-05. "A 13-year-old male was found dead in the woods subsequent to 1,1,1-trichloroethane (TCE) inhalation." 
  8. ^ Wodka, Richard M.; Jeong, Erwin W. S. (1 January 1989). "Cardiac Effects of Inhaled Typewriter Correction Fluid". Annals of Internal Medicine 110 (1): 91–92. doi:10.1059/0003-4819-110-1-91_2. PMID 2908837. Archived from the original on 2009-07-25. Retrieved 2010-01-05. 
  9. ^ Paddock, Richard C. (29 September 1989). "Gillette Agrees to Remove Toxics From Its Paper Correction Fluid". Los Angeles Times (Sacramento). Archived from the original on 22 July 2009. Retrieved 5 January 2010. 
  10. ^ Estrin, Norman F.; Akerson, James M. (2000). "Proposition 65". Cosmetic regulation in a competitive environment. New York, New York: Marcel Dekker. p. 138. ISBN 0-8247-7516-3. Retrieved 5 January 2010. "Gillette agreed to reformulate the product so that it would not pose a risk requiring a Proposition 65 warning" 

Further reading[edit]