Nitrobenzene
From Wikipedia, the free encyclopedia
| Nitrobenzene | |
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| Other names | Nitrobenzol Oil of mirbane |
| Identifiers | |
| CAS number | [98-95-3] |
| RTECS number | QJ0525000 |
| SMILES | C1=CC=C(C=C1)[N+](=O)[O-] |
| Properties | |
| Molecular formula | C6H5NO2 |
| Molar mass | 123.06 g/mol |
| Appearance | yellowish liquid |
| Density | 1.199 g/cm3 |
| Melting point |
5.85 °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) |
| R-phrases | R23/24/25, R40, R48/23/24, R51/53, R62 |
| S-phrases | (S1/2), S28, S36/37, S45, S61 |
| Flash point | 88 °C |
| Autoignition temperature |
525 °C |
| Related compounds | |
| Related compounds | Aniline Benzenediazonium Nitrosobenzene |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references |
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Nitrobenzene, also known as nitrobenzol or oil of mirbane, is an organic compound with the chemical formula C6H5NO2. This oily water-insoluble liquid, which is quite toxic, is mainly produced as a precursor to aniline. In the laboratory it finds occasional use as a solvent, especially for electrophilic reagents.
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[edit] Uses
Approximately 95% of nitrobenzene is consumed in the production of aniline.[1]
[edit] Specialized applications
More specialized applications include the use of nitrobenzene as a precursor to rubber chemicals, pesticides, dyes, and pharmaceuticals. 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)[citation needed]. Nitrobenzene is also used in Kerr cells, as it has an unusually large Kerr constant.
[edit] Organic reactions
Aside from its conversion to aniline, nitrobenzene is readily converted to related derivatives such as azobenzene,[2] nitrosobenzene,[3] and phenylhydroxylamine.[4] Substitution reactions with nitrobenzene characteristically form meta-derivatives (Mannsville 1991; Sittig 1991).
[edit] Production
Nitrobenzene is prepared by nitration of benzene with a mixture of concentrated sulfuric acid, water, and nitric acid, called "mixed acid." Its production is one of the more dangerous processes conducted in the chemical industry due to the exothermicity of the reaction (ΔH = −117 kJ/mol).[1]
There were four producers of nitrobenzene in the United States in 1991: First Chemicals Corporation, Mobay, DuPont Chemicals, and Rubicon Inc. World capacity for nitrobenzene in 1985 was ca. 1.7×106 tonnes.[1]
[edit] Mechanism of nitration
The reaction pathway entails formation of an adduct between the Lewis acidic nitronium ion, NO2+, and benzene. The nitronium ion is generated in situ via the reaction of nitric acid and an acidic dehydration agent, typically sulfuric acid:
- HNO3 + H+ ⇌ NO2+ + H2O
[edit] Safety
Nitrobenzene is highly toxic (TLV 5 mg/m3) and readily absorbed through the skin.[1]
[edit] References
- ^ a b c d Gerald Booth "Nitro Compounds, Aromatic" in "Ullmann's Encyclopedia of Industrial Chemistry" 2007; John Wiley & Sons: New York.
- ^ Bigelow, H. E.; Robinson, D. B. (1955). "Azobenzene". Org. Synth.; Coll. Vol. 3: 103.
- ^ G. H. Coleman, C. M. McCloskey, F. A. Stuart. "Nitrosobenzene". Org. Synth.; Coll. Vol. 3: 668.
- ^ O. Kamm. "Β-Phenylhydroxylamine". Org. Synth.; Coll. Vol. 1: 445.
