Carbon tetrabromide

Carbon tetrabromide, also known as tetrabromomethane, is a chemical compound with the formula CBr₄. This compound is a heavy, colorless solid that is soluble in organic solvents. It has been used in the past as a solvent for greases, waxes, and oils, in fire extinguishers, and in the manufacture of other chemicals. Due to its high density and non-polarity, carbon tetrabromide has also found use in mineral separation processes.

Properties

Carbon tetrabromide is a tetrahedral molecule, similar in structure to carbon tetrachloride. It has a molecular weight of 331.63 g/mol and a density of 3.42 g/cm³, making it one of the heavier organic compounds. Its melting point is 91°C (195.8°F), and it boils at 190°C (374°F) under standard atmospheric pressure. Carbon tetrabromide is non-flammable and exhibits low reactivity under normal conditions.

Synthesis

The synthesis of carbon tetrabromide typically involves the reaction of bromine with methane or carbon tetrachloride. The reaction with methane requires a radical initiator, such as light or heat, to proceed:

CH₄ + 4Br₂ → CBr₄ + 4HBr

When carbon tetrachloride is used, the reaction can proceed in the presence of a suitable catalyst:

CCl₄ + 4Br₂ → CBr₄ + 4Cl₂

Applications

Historically, carbon tetrabromide was used in fire extinguishers designed for electrical fires, as it is non-conductive and does not damage electrical equipment. However, its use has declined due to environmental and health concerns associated with halogenated compounds.

In the laboratory, carbon tetrabromide is used as a reagent in the preparation of certain organic compounds. It serves as a source of bromine in various bromination reactions. Additionally, its high density makes it useful for separating mineral ores through a process known as heavy liquid separation.

Safety and Environmental Concerns

Carbon tetrabromide is considered to be a potential health hazard. Exposure to this compound can cause irritation to the skin, eyes, and respiratory system. Prolonged or repeated exposure may lead to more severe health effects, including liver and kidney damage.

Environmental concerns associated with carbon tetrabromide primarily relate to its persistence in the environment and potential to bioaccumulate. As with other halogenated compounds, carbon tetrabromide can undergo long-range atmospheric transport, leading to its deposition in remote areas.

Regulation

Due to its environmental and health impacts, the use and production of carbon tetrabromide are regulated under various international agreements and national regulations. Efforts are ongoing to find safer alternatives for applications that have traditionally relied on this compound.

See Also

• Halogenation
• Organobromine compound
• Heavy liquid separation
• Environmental impact of halogenated compounds