Nitrobenzene

Nitrobenzene
Names
Other names
Nitrobenzol
Oil of mirbane
Identifiers
98-95-3 YesY
3D model (Jmol) Interactive image
ChEBI CHEBI:27798 YesY
ChEMBL ChEMBL15750 YesY
ChemSpider 7138 YesY
ECHA InfoCard 100.002.469
KEGG C06813 YesY
PubChem 7416
RTECS number DA6475000
UNII E57JCN6SSY N
Properties
C6H5NO2
Molar mass 123.06 g/mol
Appearance yellowish, oily liquid[1]
Odor pungent, like paste shoe polish[1]
Density 1.199 g/cm3
Melting point 5.7 °C (42.3 °F; 278.8 K)
Boiling point 210.9 °C (411.6 °F; 484.0 K)
0.19 g/100 ml at 20 °C
Vapor pressure 0.3 mmHg (25°C)[1]
Hazards
T F N
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 2: Must be moderately heated or exposed to relatively high ambient temperature before ignition can occur. Flash point between 38 and 93 °C (100 and 200 °F). E.g., diesel fuel Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas 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
2
3
1
Flash point 88 °C (190 °F; 361 K)
480 °C (896 °F; 753 K)
Explosive limits 1.8%-?[1]
Lethal dose or concentration (LD, LC):
780 mg/kg (rat, oral)
600 mg/kg (rat, oral)
590 mg/kg (mouse, oral)
[2]
750 mg/kg (dog, oral)[2]
US health exposure limits (NIOSH):
PEL (Permissible)
 TWA 1 ppm (5 mg/m3) [skin][1]
REL (Recommended)
 TWA 1 ppm (5 mg/m3) [skin][1]
IDLH (Immediate danger)
 200 ppm[1]
Related compounds
Related compounds
 Aniline
Benzenediazonium chloride
Nitrosobenzene
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YesYN ?)
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

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).[3]

World capacity for nitrobenzene in 1985 was about 1.7×106 tonnes.[3]

Mechanism of nitration

The nitration process involves formation of 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+ ⇌ NO2+ + H2O

Uses

Approximately 97% of nitrobenzene is consumed in the production of aniline,[3] which is a precursor to rubber chemicals, pesticides, dyes (particularly azo dyes), explosives, and pharmaceuticals.

Specialized applications

Nitrobenzene is also used to mask unpleasant odors in shoe and floor polishes, leather dressings, paint solvents, and other materials. 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).[4] Nitrobenzene is also used in Kerr cells, as it has an unusually large Kerr constant.

Organic reactions

Aside from its conversion to aniline, nitrobenzene is readily converted to related derivatives such as azobenzene,[5] nitrosobenzene,[6] and phenylhydroxylamine.[7] The nitro- group is deactivating, thus substitution tends to occur at the meta-position.

Safety

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,[8] and is classified by the IARC as a Group 2B carcinogen which is "possibly carcinogenic to humans".[9] It has been shown to cause liver, kidney, and thyroid adenomas and carcinomas in rats.[10]

It is classified as an extremely hazardous substance in the United States as defined in Section 302 of the U.S. Emergency Planning and Community Right-to-Know Act (42 U.S.C. 11002), and is subject to strict reporting requirements by facilities which produce, store, or use it in significant quantities.[11]

References

  1. 1 2 3 4 5 6 7 "NIOSH Pocket Guide to Chemical Hazards #0450". National Institute for Occupational Safety and Health (NIOSH).
  2. 1 2 "Nitrobenzene". Immediately Dangerous to Life and Health. National Institute for Occupational Safety and Health (NIOSH).
  3. 1 2 3 Gerald Booth (2007). "Nitro Compounds, Aromatic". In: Ullmann's Encyclopedia of Industrial Chemistry. John Wiley & Sons: New York. doi:10.1002/14356007.a17_411
  4. ↑ 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.
  5. ↑ Bigelow, H. E.; Robinson, D. B. (1955). "Azobenzene". Org. Synth.; Coll. Vol., 3, p. 103
  6. 1 2 G. H. Coleman, C. M. McCloskey, F. A. Stuart. "Nitrosobenzene". Org. Synth.; Coll. Vol., 3, p. 668
  7. ↑ O. Kamm. "β-Phenylhydroxylamine". Org. Synth.; Coll. Vol., 1, p. 445
  8. ↑ http://cfpub.epa.gov/ncea/iris/index.cfm?fuseaction=iris.showQuickView&substance_nmbr=0079
  9. ↑ Agents Classified by the IARC Monographs, International Agency for Research on Cancer
  10. ↑ National Institutes of Health · U.S. Department of Health and Human Services, Nomination: Nitrobenzene Review committee, 02/02/2010
  11. ↑ "40 C.F.R.: Appendix A to Part 355—The List of Extremely Hazardous Substances and Their Threshold Planning Quantities" (PDF) (July 1, 2008 ed.). Government Printing Office. Retrieved October 29, 2011.
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