Chemistry:Nitrobenzene

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Nitrobenzene is an aromatic nitro compound and the simplest of the nitrobenzenes, 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. As confirmed by X-ray crystallography, nitrobenzene is a planar molecule.[1]

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).[2]

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 by the reaction of nitric acid and an acidic dehydration agent, typically sulfuric acid:

HNO3 + H+ ⇌ NO2+ + H2O

World capacity for nitrobenzene in 1985 was about 1,700,000 tonnes.[2]

Uses

Approximately 95% of nitrobenzene industrially produced is hydrogenated to aniline:[2]

C6H5NO2 + 3 H2 → C6H5NH2 + 2 H2O

Aniline is a precursor to urethane polymers, rubber chemicals, pesticides, dyes (particularly azo dyes), explosives, and pharmaceuticals.

Most aniline is consumed in the production of methylenedianiline, a precursor to polyurethanes.

Specialized applications

Nitrobenzene is used to mask unpleasant odors in shoe and floor polishes, leather dressings, paint solvents, and other materials. Redistilled, as oil of mirbane, nitrobenzene had been used as an inexpensive perfume for soaps. It has been replaced by less toxic chemicals for this purpose.[3] A significant merchant market for nitrobenzene is its use in the production of the analgesic paracetamol (also known as acetaminophen).[4] Nitrobenzene is also used in Kerr cells, as it has an unusually large Kerr constant. Evidence suggests its use in agriculture as a plant growth/flowering stimulant.[5]

Chemical properties

Electrophilic substitution

Nitrobenzene can be further nitrated using a mixture of concentrated HNO3 and H2SO4 to produce 1,3-dinitrobenzene (1,3-DNB) as a major product. Typical byproducts of the reaction are 1,2-dinitrobenzene (1,2-DNB), 1,4-dinitrobenzene (1,4-DNB) and 4-nitrophenol (4-NP).[6]

Sulfonation of nitrobenzene with 65% fuming sulfuric acid gives 3-nitrobenzenesulfonic acid (3-NBSA). Usually 3-NBSA is not isolated in a form of a free acid, the reaction mass is quenched and converted to the sodium salt of 3-NBSA.[7][8]

Nitrobenzene chlorination in the presence of FeCl3 yields a mixture that predominantly contains 3-nitrochlorobenzene (3-NCB) and small amount of the other isomers: 2-nitrochlorobenzene (2-NCB) and 4-nitrochlorobenzene (4-NCB).[9]

Other organic reactions

Aside from its conversion to aniline, nitrobenzene can be selectively reduced to azoxybenzene,[10] azobenzene,[11] nitrosobenzene,[12]Org. Synth. 1945, 25, 80 DOI: 10.15227/orgsyn.025.0080 hydrazobenzene,[13] and phenylhydroxylamine.[14] It has been used as a mild oxidant in reactions like the Skraup quinoline synthesis.[15]

Safety

Nitrobenzene is 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.

Nitrobenzene is considered a likely human carcinogen by the United States Environmental Protection Agency,[16] and is classified by the IARC as a Group 2B carcinogen which is "possibly carcinogenic to humans".[17] It has been shown to cause liver, kidney, and thyroid adenomas and carcinomas in rats.[18]

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.[19]

References

  1. ↑ Olga V. Dorofeeva; Yuriy V. Vishnevskiy; Natalja Vogt; Jürgen Vogt; Lyudmila V. Khristenko; Sergey V. Krasnoshchekov; Igor F. Shishkov; István Hargittai et al. (2007). "Molecular Structure and Conformation of Nitrobenzene Reinvestigated by Combined Analysis of Gas-Phase Electron Diffraction, Rotational Constants, and Theoretical Calculations". Structural Chemistry 18 (6): 739–753. doi:10.1007/s11224-007-9186-6. Bibcode: 2007StrCh..18..739D. 
  2. ↑ 2.0 2.1 2.2 Booth, Gerald (2007). "Nitro Compounds, Aromatic". Ullmann's Encyclopedia of Industrial Chemistry (6th ed.). Weinheim: Wiley-VCH. doi:10.1002/14356007.a17_411. ISBN 978-3-527-30385-4. 
  3. ↑ "a case of poisoning by oil of mirbane (nitro-benzol)". British Medical Journal 1 (2665): 183. January 1912. doi:10.1136/bmj.1.2665.183. PMID 20765985. 
  4. ↑ Bhattacharya, Apurba; Purohit, Vikram C.; Suarez, Victor; Tichkule, Ritesh; Parmer, Gaurang; Rinaldi, Frank (March 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. ↑ "Flowering stimulant composition using nitrobenzene". https://patents.google.com/patent/US9113628. 
  6. ↑ Wiley-VCH, ed (2003-03-11) (in en). Ullmann's Encyclopedia of Industrial Chemistry (1 ed.). Wiley. doi:10.1002/14356007.a17_411. ISBN 978-3-527-30385-4. https://onlinelibrary.wiley.com/doi/book/10.1002/14356007. 
  7. ↑ , Arthur Aloysius & Leonard Aaron Rothman"Process for preparing sodium-m-nitrobenzenesulfonate" patent EP0010443B1, issued 1982-10-20
  8. ↑ Chen, Yizheng; Su, Yuanhai; Jiao, Fengjun; Chen, Guangwen (2012-06-13). "A simple and efficient synthesis protocol for sulfonation of nitrobenzene under solvent-free conditions via a microreactor" (in en). RSC Advances 2 (13): 5637–5644. doi:10.1039/C2RA20406A. ISSN 2046-2069. https://pubs.rsc.org/en/content/articlelanding/2012/ra/c2ra20406a. 
  9. ↑ Wiley-VCH, ed (2003-03-11) (in en). Ullmann's Encyclopedia of Industrial Chemistry (1 ed.). Wiley. doi:10.1002/14356007.a17_411. ISBN 978-3-527-30385-4. https://onlinelibrary.wiley.com/doi/book/10.1002/14356007. 
  10. ↑ Bigelow, H. E.; Palmer, Albert (1931). "Azoxybenzene". Organic Syntheses 11: 16. doi:10.15227/orgsyn.011.0016. 
  11. ↑ "Azobenzene". Organic Syntheses. 1955. http://www.orgsyn.org/demo.aspx?prep=CV3P0103. ; Collective Volume, 3, pp. 103 
  12. ↑ "Nitrosobenzene". Organic Syntheses 25: 80. 1945. doi:10.15227/orgsyn.025.0080. 
  13. ↑ Karwa, Shrikant L.; Rajadhyaksha, Rajeev A. (January 1988). "Selective catalytic hydrogenation of nitrobenzene to hydrazobenzene" (in EN). Industrial & Engineering Chemistry Research 27 (1): 21–24. doi:10.1021/ie00073a005. ISSN 0888-5885. 
  14. ↑ "β-Phenylhydroxylamine". Organic Syntheses. http://www.orgsyn.org/demo.aspx?prep=cv1p0445. ; Collective Volume, 1, pp. 445 
  15. ↑ Clarke, HT; Davis, AW. "Quinoline". Organic Syntheses 1: 478. http://www.orgsyn.org/demo.aspx?prep=CV1P0478. 
  16. ↑ Division, US EPA, ORD, Integrated Risk Information System. "Nitrobenzene CASRN 98-95-3 - IRIS - US EPA, ORD". http://cfpub.epa.gov/ncea/iris/index.cfm?fuseaction=iris.showQuickView&substance_nmbr=0079. 
  17. ↑ "Agents Classified by the IARC Monographs, International Agency for Research on Cancer". http://monographs.iarc.fr/ENG/Classification/ClassificationsGroupOrder.pdf. 
  18. ↑ National Institutes of Health · U.S. Department of Health and Human Services, Nomination: Nitrobenzene Review committee, 02/02/2010
  19. ↑ "40 C.F.R.: Appendix A to Part 355—The List of Extremely Hazardous Substances and Their Threshold Planning Quantities". Government Printing Office. http://edocket.access.gpo.gov/cfr_2008/julqtr/pdf/40cfr355AppA.pdf. 



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