Chlorobenzene

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Chlorobenzene
Chlorobenzene2.svg
Chlorobenzene
Chlorobenzene.png
Names
IUPAC name
chlorobenzene
Other names
benzene chloride
monochlorobenzene
Phenyl chloride
Chlorobenzol
MCB
Identifiers
108-90-7 YesY
ChEBI CHEBI:28097 YesY
ChEMBL ChEMBL16200 YesY
ChemSpider 7676 YesY
Jmol-3D images Image
KEGG C06990 YesY
PubChem 7964
RTECS number CZ0175000
UNII K18102WN1G YesY
Properties
C6H5Cl
Molar mass 112.56 g/mol
Appearance colorless liquid
Odor almond-like[1]
Density 1.11 g/cm³, liquid
Melting point −45 °C (−49 °F; 228 K)
Boiling point 131 °C (268 °F; 404 K)
0.5 g l−1 in water at 20 °C
Solubility in other solvents soluble in most organic solvents
Vapor pressure 9 mmHg[1]
Hazards
MSDS External MSDS
R-phrases R10 R20 R51/53
S-phrases S24/25 S61
NFPA 704
Flammability code 3: Liquids and solids that can be ignited under almost all ambient temperature conditions. Flash point between 23 and 38 °C (73 and 100 °F). E.g., gasoline) Health code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroform Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point 29 °C (84 °F; 302 K)
Explosive limits 1.3%-9.6%[1]
US health exposure limits (NIOSH):
TWA 75 ppm (350 mg/m3)[1]
none[1]
1000 ppm[1]
Related compounds
Related Halobenzenes
Fluorobenzene
Bromobenzene
Iodobenzene
Related compounds
benzene
1,4-dichlorobenzene
Supplementary data page
Refractive index (n),
Dielectric constantr), etc.
Thermodynamic
data
Phase behaviour
solid–liquid–gas
UV, IR, NMR, MS
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

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.[2]

Uses[edit]

Historical[edit]

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.[3] Chlorobenzene is nitrated on a large scale to give a mixture of 2-nitrochlorobenzene and 4-nitrochlorobenzene , which are separated. These mononitrochlorobenzenes are converted to related 2-nitrophenol, 2-nitroanisole, bis(2-nitrophenyl)disulfide, and 2-nitroaniline by nucleophilic displacement of the chloride, with respectively sodium hydroxide, sodium methoxide, sodium disulfide, and ammonia. The conversions of the 4-nitro derivative are similar.[4]

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:[5]

C6H5Cl + NaOH → C6H5OH + NaCl

Production[edit]

It was first described in 1851. Chlorobenzene is manufactured by chlorination of benzene in the presence of a catalytic amount of Lewis acid such as ferric chloride, sulfur dichloride, and anhydrous aluminium chloride:[2]

Chlorination benzene.svg

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.

Laboratory routes[edit]

Chlorobenzene can be produced by from aniline via benzenediazonium chloride, the route being known as the Sandmeyer reaction.

Safety[edit]

Chlorobenzene exhibits "low to moderate" toxicity as indicated by its LD50 of 2.9 g/kg.[3] The Occupational Safety and Health Administration has set a permissible exposure limit at 75 ppm (350 mg/m3) over an eight hour time-weighted average for workers handling chlorobenzene.[6]

Toxicology and biodegradation[edit]

Chlorobenzene 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. The bacterium Rhodococcus phenolicus degrades chlorobenzene as sole carbon sources.[7]

Upon entering the body, typically via contaminated air, chlorobenzene is excreted both via the lungs and the urinary system.

On other planets[edit]

In December 2014, a team of scientists announced that the Curiosity rover reported evidence of higher concentrations of chlorobenzene in a rock, named "Cumberland", on Mars. The team speculated that the chlorobenzene might have been produced by Martian life, or by other chemical reactions, resulting from the heating of the rock and outgassing.[8][9]

Comparison of Organics in Martian rocks - Chlorobenzene levels were much higher in the "Cumberland" rock sample.
Detection of Organics in the "Cumberland" rock sample.
Spectral Analysis (SAM) of "Cumberland" rock.

References[edit]

  1. ^ a b c d e f "NIOSH Pocket Guide to Chemical Hazards #0121". National Institute for Occupational Safety and Health (NIOSH). 
  2. ^ a b U. Beck, E. Löser "Chlorinated Benzenes and other Nucleus-Chlorinated Aromatic Hydrocarbons" Ullmann's Encyclopedia of Industrial Chemistry, 2012, Wiley-VCH, Weinheim. doi:10.1002/14356007.o06_o03
  3. ^ a b Rossberg, Manfred; Lendle, Wilhelm; Pfleiderer, Gerhard; Tögel, Adolf; Dreher, Eberhard-Ludwig; Langer, Ernst; Rassaerts, Heinz; Kleinschmidt, Peter; Strack, Heinz; Cook, Richard; Beck, Uwe; Lipper, Karl-August; Torkelson, Theodore R.; Löser, Eckhard; Beutel, Klaus K.; Mann, Trevor (2006). "Ullmann's Encyclopedia of Industrial Chemistry - Chlorinated Hydrocarbons". doi:10.1002/14356007.a06_233.pub2. ISBN 3527306730. 
  4. ^ Booth, Gerald (2000). "Ullmann's Encyclopedia of Industrial Chemistry - Nitro Compounds, Aromatic". doi:10.1002/14356007.a17_411. ISBN 3527306730. 
  5. ^ Weber, Manfred; Weber, Markus; Kleine-Boymann, Michael (2004). "Ullmann's Encyclopedia of Industrial Chemistry - Phenol". doi:10.1002/14356007.a19_299.pub2. ISBN 3527306730. 
  6. ^ CDC - NIOSH Pocket Guide to Chemical Hazards
  7. ^ Rehfuss, M.; Urban, J. (2005). "Rhodococcus phenolicus sp. nov., a novel bioprocessor isolated actinomycete with the ability to degrade chlorobenzene, dichlorobenzene and phenol as sole carbon sources". Systematic and Applied Microbiology 28 (8): 695–701. doi:10.1016/j.syapm.2005.05.011. PMID 16261859.  edit Erratum: Rehfuss, M. (2006). "Erratum to "Rhodococcus phenolicus sp. nov., a novel bioprocessor isolated actinomycete with the ability to degrade chlorobenzene, dichlorobenzene and phenol as sole carbon sources" [Systematic and Applied Microbiology 28 (2005) 695–701]". Systematic and Applied Microbiology 29 (2): 182–110. doi:10.1016/j.syapm.2005.11.005.  edit
  8. ^ Webster, Guy; Jones, Nancy Neal; Brown, Dwayne (December 16, 2014). "NASA Rover Finds Active and Ancient Organic Chemistry on Mars". NASA. Retrieved December 16, 2014. 
  9. ^ Chang, Kenneth (December 16, 2014). "‘A Great Moment’: Rover Finds Clue That Mars May Harbor Life". New York Times. Retrieved December 16, 2014.