Mono Chloro Benzene(CAS: 108-90-7)
Colorless, transparentvolatile liquid
Chlorobenzene is an aromatic organic compound with the chemical formula C6H5Cl. This colorless, flammable liquid is a common solvent and a widely used intermediate in the manufacture of other chemicals.
Chlorobenzene once was used in the manufacture of certain pesticides, most notably DDT by reaction with chloral (trichloroacetaldehyde), but this application has declined with the diminished use of DDT. At one time, chlorobenzene was the main precursor for the manufacture of phenol:
C6H5Cl + NaOH → C6H5OH + NaCl
The major use of chlorobenzene is as an intermediate in the production of commodities such as herbicides, dyestuffs, and rubber. Chlorobenzene is also used as a high-boiling solvent in many industrial applications as well as in the laboratory. Chlorobenzene is nitrated on a large scale to give a mixture of 2- and 4-nitrochlorobenzenes, which can be separated by fractional crystallization followed by distillation. 2-Nitrochlorobenzene (CAS#88-73-3) is converted to related 2-nitrophenol, 2-nitroanisole, bis(2-nitrophenyl)disulfide, and 2-nitroaniline by nucleophilic displacement of the chloride with sodium hydroxide, sodium methoxide, sodium disulfide and ammonia. The conversion of the 4-nitrochlorobenzene (CAS#100-00-5) are similar.
Chlorobenzene was first described in 1851. Presently it is manufactured by chlorination of benzene in the presence of a catalytic amount of Lewis acidsuch as ferric chloride, sulfur dichloride, and anhydrous aluminium chloride:
The catalyst enhances the electrophilicity of the chlorine. Because chlorine is electronegative, C6H5Cl exhibits somewhat decreased susceptibility to further chlorination. Industrially the reaction is conducted as a continuous process to minimize the formation of dichlorobenzenes.
Rhodococcus phenolicus is a bacterium species able to degrade chlorobenzene as sole carbon sources.
Chlorobenzene exhibits "low to moderate" toxicity as indicated by its LD50 of 2.9 g/kg. The Occupational Safety and Health Administration has set apermissible exposure limit at 75 ppm (350 mg/m3) over an eight hour time-weighted average for workers handling chlorobenzene.
Chlorobenzene is not a naturally occurring compound, but because of its manufacture, can persist in soil for several months, in air for about 3.5 days, and in water for less than one day. Humans may be exposed to this agent via breathing contaminated air (primarily via occupational exposure), eating contaminated food or water, or by coming into contact with contaminated soil (typically near hazardous waste sites). However, because it has only been found at 97 out of 1,177 NPL hazardous waste sites, it is not considered a widespread environmental contaminant.
Upon entering the body, typically via contaminated air, chlorobenzene is excreted both via the lungs and the urinary system.