What Is Trichloroethane?
Trichloroethane is an organic halogen compound with the molecular formula C2H3Cl3.
It is classified into two types, 1,1,1-trichloroethane, and 1,1,2-trichloroethane, based on the position of the chlorine atom. 1,1,1-trichloroethane, also known as chlorotene or methyl chloroform, exists as a colorless liquid at room temperature.
It irritates human skin and eyes and is designated as a hazardous substance to be labeled or notified by name under various laws.
Uses of Trichloroethane
1,1,1-trichloroethane, due to its ability to dissolve various organic compounds, was extensively used as an organic solvent for cleaning electronic components and as a paint solvent. However, its use has been largely discontinued worldwide since its classification as an ozone-depleting substance under the Montreal Protocol.
Properties of Trichloroethane
1,1,1-trichloroethane has a melting point of -30°C and a boiling point of 74°C. It is volatile and possesses excellent cleaning capabilities.
While generally classified as a nonpolar solvent, it exhibits a slight degree of polarity due to the presence of three chlorine atoms with high electronegativity, which are biased to one side of the molecule.
Structure of Trichloroethane
1,1,1-trichloroethane and 1,1,2-trichloroethane are structurally related isomers, both featuring three of the four hydrogen atoms attached to the carbon atom of ethane replaced by a chlorine atom.
The molecular formula of 1,1,1-trichloroethane is CH3CCl3, with a molecular weight of 133.40 and a density of 1.34g/cm3.
Other Information on Trichloroethane
1. Synthesis of 1,1,1-Trichloroethane
1,1,1-trichloroethane can be industrially synthesized in two steps from the raw material chloroethylene. First, chloroethylene reacts with hydrogen chloride at 20-50°C, using catalysts like aluminum chloride, iron (III) chloride, or zinc chloride, to produce 1,1-dichloroethane. Subsequently, 1,1-dichloroethane reacts with chlorine under UV irradiation to yield 1,1,1-trichloroethane.
The yield is approximately 80-90%, with the generated hydrogen chloride being reusable. Although the main byproduct is the structural isomer 1,1,2-trichloroethane, it can be separated by distillation.
A small amount of 1,1,1-trichloroethane can also be obtained from the reaction of 1,1-dichloroethene (vinylidene chloride) with hydrogen chloride using iron (III) chloride as a catalyst.
2. Presence of 1,1,1-Trichloroethane in the Atmosphere
The Montreal Protocol identified 1,1,1-trichloroethane as one of the compounds contributing to ozone layer depletion, leading to its global prohibition starting in 1996. Consequently, its atmospheric concentration is rapidly declining due to its relatively short lifespan of 5 years.
3. Characteristics of 1,1,2-Trichloroethane
Also known as trichloroethane, 1,1,2-trichloroethane has a melting point of -6°C and a boiling point of 114°C. With a molecular weight of 133.40 and a density of 1.44g/cm3, it appears as a colorless liquid at room temperature, emitting a sweet aroma. Its specific formula is C2H3Cl3.
It exhibits a central nervous system depressant effect, with inhalation leading to symptoms such as headache and nausea. Unlike 1,1,1-trichloroethane, 1,1,2-trichloroethane is not designated as an ozone-depleting substance. Therefore, it continues to be utilized as an organic solvent and serves as a synthetic intermediate of 1,1-dichloroethane.