What Is Carbon Tetrachloride?
Carbon tetrachloride (CCl4) is a colorless, dense, and volatile liquid with a characteristic sweet odor resembling chloroform. It is a valuable feedstock for the synthesis of many important commercial chemicals, particularly chlorinated propanes used to produce hydrofluoroolefins (HFOs).
Compositions of Carbon Tetrachloride
Chemical Composition and Structure
Carbon tetrachloride (CCl4) is a covalent compound composed of one carbon atom and four chlorine atoms. It has a tetrahedral molecular geometry with the carbon atom at the center and the four chlorine atoms at the vertices, forming four C-Cl bonds. The molecular formula is CCl4, and its molar mass is 153.82 g/mol.
Physical Properties
It has a boiling point of 76.8°C, a melting point of -22.6°C, and a density of 1.594 g/cm3 at 20°C. It is non-flammable, non-explosive, and relatively stable under normal conditions.
Reactivity
Carbon tetrachloride (CCl4) is generally inert and unreactive under normal conditions due to the stability of the carbon-chlorine bonds. However, it can undergo certain reactions, such as photochemical dissociation, thermal decomposition, and reactions with strong reducing agents or bases.
Uses & Benefits of Carbon Tetrachloride
Applications of Carbon Tetrachloride
Chemical Synthesis
- Carbon tetrachloride is widely used as a solvent and reagent in organic synthesis, particularly for chlorination reactions.
- It serves as a feedstock for the production of chlorinated propanes, which are precursors for hydrofluoroolefins (HFOs).
Pharmaceutical Industry
- Carbon tetrachloride finds applications in the synthesis of various pharmaceutical intermediates and active ingredients.
- It is employed as a solvent in certain pharmaceutical processes.
Refrigerants and Aerosols
- Historically, carbon tetrachloride was used as a refrigerant and in the manufacturing of aerosol sprays.
- However, its use in these applications has been phased out due to its ozone-depleting potential.
Benefits of Carbon Tetrachloride
Versatile Solvent
- Carbon tetrachloride is an excellent non-polar solvent, capable of dissolving a wide range of organic compounds.
- Its inert nature and low reactivity make it suitable for various chemical processes.
Feedstock for Chemical Production
- As a valuable feedstock, carbon tetrachloride enables the synthesis of important commercial chemicals, such as chlorinated propanes and HFOs.
Educational and Research Applications
- Carbon tetrachloride finds applications in chemical experiments and demonstrations due to its unique properties, providing educational benefits.
Synthesis of Carbon Tetrachloride
Chlorination Reactions
The most common industrial method involves the chlorination of hydrocarbons or chlorinated hydrocarbons, often using chlorine gas:
- Chlorination of methane: CH4 + 4Cl2 → CCl4 + 4HCl
- Chlorination of carbon disulfide: CS2 + 3Cl2 → CCl4 + S2Cl2
Photochemical Synthesis
Carbon tetrachloride can be produced through the oxidative photolysis of chlorinated hydrocarbons in the presence of oxygen, followed by reaction with an alcohol and the addition of a base.
Other Methods
- Halogen exchange reactions with fluorinated or brominated reagents
- Hydrolysis of chlorinated hydrocarbons
- Reactions of metal carbides with hydrogen chloride
Safety Information of Carbon Tetrachloride
Toxicity and Health Hazards
Carbon tetrachloride (CCl4) is highly toxic and poses severe health risks. Inhalation or ingestion can cause liver and kidney damage, as well as depression of the central nervous system. Prolonged exposure may lead to coma or death. It is classified as a potential carcinogen and is regulated as a hazardous substance. Proper protective equipment and handling procedures are essential when working with carbon tetrachloride.
Environmental Impacts
Carbon tetrachloride is an ozone-depleting substance and is regulated under the Montreal Protocol. Its release into the environment contributes to the depletion of the ozone layer, which protects the Earth from harmful ultraviolet radiation. It is also toxic to aquatic organisms and can persist in the environment for an extended period.
Disposal and Treatment
Due to its hazardous nature, carbon tetrachloride waste must be properly disposed of or treated. Common methods include incineration, hydrolysis, and chemical reactions with methanol, methane, hydrogen, or other reactants. These processes aim to convert carbon tetrachloride into less harmful substances or recover valuable byproducts. Proper waste management practices are crucial to minimize environmental and health risks.
Regulations and Guidelines
Carbon tetrachloride is subject to various federal and state regulations due to its toxicity and environmental impacts. These regulations govern its production, use, storage, transportation, and disposal. Exposure limits and safety guidelines have been established by organizations such as OSHA and NIOSH to protect workers and the general public. Compliance with these regulations is mandatory to ensure safe handling and minimize risks.
In summary, carbon tetrachloride poses significant health and environmental hazards, necessitating strict safety measures, proper disposal methods, and adherence to regulations during its production, use, and handling. Its phase-out and replacement with safer alternatives are ongoing efforts to mitigate its negative impacts.
Latest innovations of Carbon Tetrachloride
Continuous Preparation Methods
Continuous preparation methods have been developed for producing chlorohydrocarbons from carbon tetrachloride and olefins. These methods isolate the ferrous complex catalyst preparation and chlorohydrocarbon synthesis reactions to prevent olefin autopolymerization and catalyst deactivation. By controlling reaction parameters like temperature, time, and pressure, higher reaction efficiency, yield, and selectivity can be achieved.
Hydrodechlorination Processes
Liquid-phase hydrodechlorination of carbon tetrachloride on Pd/carbon catalysts has been studied for selective conversion to chloroform. The reaction follows a zero-order kinetics up to 60% conversion at 413 K, with chloroform selectivity >90% even at high conversions. A reaction pathway involving parallel paths for chloroform, hexachloroethane, and methane formation has been proposed. Gas-phase hydrodechlorination using Pt-Ir binary catalysts, optionally promoted with Sn, Ti, Ge, Re, etc., reduces by-product formation and extends catalytic activity.
Chlorine-Hydrogen Exchange
A chlorine-hydrogen exchange method has been developed for converting carbon tetrachloride into chloroform under mild conditions using a phase transfer catalyst (e.g., tetrabutylammonium fluoride) and hydrogen donors like trichloroethylene, acetylene, or succinimide. This noble metal-free process exhibits high conversion and selectivity, enabling recycling and valorization of carbon tetrachloride.
Plasma-Assisted Conversion
Non-equilibrium plasma at atmospheric pressure has been explored for converting carbon tetrachloride into a non-hazardous, potentially valuable commodity by reacting it with methane. This non-oxidative process forms a chlorinated polymer, with the reaction pathways elucidated through experimental results and quantum chemical calculations.
Microwave-Assisted Carbohydrochlorination
Microwave-assisted carbohydrochlorination reactions between hydrogen chloride and element oxides (e.g., SiO2, B2O3, Al2O3, Fe2O3, P2O5, TiO2) in the presence of carbon sources have been developed for direct synthesis of element chlorides like SiCl4, BCl3, AlCl3, FeCl2, PCl3, and TiCl4. This one-step process occurs at lower temperatures, shorter reaction times, and higher yields compared to conventional methods.
To get detailed scientific explanations of carbon tetrachloride, try Patsnap Eureka.
