Nitrobenzene

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Nitrobenzene
Nitrobenzene Nitrobenzene
Sample of Nitrobenzene.jpg
Identifiers
CAS number 98-95-3 YesY
PubChem 7416
ChemSpider 7138 YesY
UNII E57JCN6SSY N
KEGG C06813 YesY
ChEBI CHEBI:27798 YesY
ChEMBL CHEMBL15750 YesY
RTECS number DA6475000
Jmol-3D images Image 1
Properties
Molecular formula C6H5NO2
Molar mass 123.06 g/mol
Appearance yellowish liquid
Density 1.199 g/cm3
Melting point 5.7 °C
Boiling point 210.9 °C
Solubility in water 0.19 g/100 ml at 20 °C
Hazards
EU classification Toxic (T)
Carc. Cat. 3
Repr. Cat. 3
Dangerous for the environment (N)
Flammable(F)
R-phrases R10, R23/24/25, R40,
R48/23/24, R51/53, R62
S-phrases (S1/2), S28, S36/37,
S45, 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 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g., calcium Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point 88 °C (190 °F; 361 K)
Related compounds
Related compounds Aniline
Benzenediazonium chloride
Nitrosobenzene
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N (verify) (what is: YesY/N?)
Infobox references

Nitrobenzene is an organic compound with the chemical formula C6H5NO2. It is a water-insoluble pale yellow oil with an almond-like odor. It freezes to give greenish-yellow crystals. It is produced on a large scale from benzene as a precursor to aniline. In the laboratory, it is occasionally used as a solvent, especially for electrophilic reagents.

Production[edit]

Nitrobenzene is prepared by nitration of benzene with a mixture of concentrated sulfuric acid, water, and nitric acid. This mixture is sometimes called "mixed acid." The production of nitrobenzene is one of the most dangerous processes conducted in the chemical industry because of the exothermicity of the reaction (ΔH = −117 kJ/mol).[1]

NitrationofPh.png

World capacity for nitrobenzene in 1985 was about 1.7×106 tonnes.[1]

Mechanism of nitration[edit]

The nitration process involves formation the nitronium ion (NO2+), followed by an electrophilic aromatic substitution reaction of it with benzene. The nitronium ion is generated in situ by the reaction of nitric acid and an acidic dehydration agent, typically sulfuric acid:

HNO3 + H+ is in equilibrium with NO2+ + H2O

Uses[edit]

Approximately 95% of nitrobenzene is consumed in the production of aniline,[1] which is a precursor to rubber chemicals, pesticides, dyes (particularly azo dyes), explosives, and pharmaceuticals.

Specialized applications[edit]

Nitrobenzene is also used in shoe and floor polishes, leather dressings, paint solvents, and other materials to mask unpleasant odors. Redistilled, as oil of mirbane, nitrobenzene has been used as an inexpensive perfume for soaps. A significant merchant market for nitrobenzene is its use in the production of the analgesic paracetamol (also known as acetaminophen) (Mannsville 1991).[2] Nitrobenzene is also used in Kerr cells, as it has an unusually large Kerr constant.

Organic reactions[edit]

Aside from its conversion to aniline, nitrobenzene is readily converted to related derivatives such as azobenzene,[3] nitrosobenzene,[4] and phenylhydroxylamine.[5] The nitro- group is deactivating, thus substitution tends to occur at the meta-position.

Safety[edit]

Nitrobenzene is highly toxic (Threshold Limit Value 5 mg/m3) and readily absorbed through the skin.

Prolonged exposure may cause serious damage to the central nervous system, impair vision, cause liver or kidney damage, anemia and lung irritation. Inhalation of vapors may induce headache, nausea, fatigue, dizziness, cyanosis, weakness in the arms and legs, and in rare cases may be fatal. The oil is readily absorbed through the skin and may increase heart rate, cause convulsions or rarely death. Ingestion may similarly cause headaches, dizziness, nausea, vomiting and gastrointestinal irritation, loss of sensation/use in limbs and also causes internal bleeding.[6]

Nitrobenzene is considered a likely human carcinogen by the United States Environmental Protection Agency,[7] and is classified by the IARC as a Group 2B carcinogen which is "possibly carcinogenic to humans".[8] It has been shown to cause liver, kidney, and thyroid adenomas and carcinomas in rats.[9]

References[edit]

  1. ^ a b c Gerald Booth (2007). "Nitro Compounds, Aromatic". In: Ullmann's Encyclopedia of Industrial Chemistry. John Wiley & Sons: New York. doi:10.1002/14356007.a17_411
  2. ^ Bhattacharya A.; Purohit V. C.; Suarez, V.; Tichkule, R; Parmer, G.; Rinaldi, F. (2006). "One-step reductive amidation of nitro arenes: application in the synthesis of Acetaminophen". Tetrahedron Letters 47 (11): 1861–1864. doi:10.1016/j.tetlet.2005.09.196. 
  3. ^ Bigelow, H. E.; Robinson, D. B. (1955), "Azobenzene", Org. Synth. ; Coll. Vol. 3: 103 
  4. ^ G. H. Coleman, C. M. McCloskey, F. A. Stuart, "Nitrosobenzene", Org. Synth. ; Coll. Vol. 3: 668 
  5. ^ O. Kamm, "β-Phenylhydroxylamine", Org. Synth. ; Coll. Vol. 1: 445 
  6. ^ G. H. Coleman, C. M. McCloskey, F. A. Stuart, "Nitrosobenzene", Org. Synth. ; Coll. Vol. 3: 668 
  7. ^ http://cfpub.epa.gov/ncea/iris/index.cfm?fuseaction=iris.showQuickView&substance_nmbr=0079
  8. ^ Agents Classified by the IARC Monographs, International Agency for Research on Cancer
  9. ^ National Institutes of Health · U.S. Department of Health and Human Services, Nomination: Nitrobenzene Review committee, 02/02/2010

External links[edit]