Nitrobenzene (chemical formula: C6H4NO2) is a yellowish, oily, aromatic nitro-compound. The most important application of nitrobenzene (consuming 95%) is for the manufacturing of aniline, which is an important industrial precursor. Besides aniline, it can also be used to generate related derivatives such as azobenzene, nitrosobenzene and phenylhydroxylamine. Moreover, it can be used for the production of lubricating oils, dyes, drugs, pesticides, and synthetic rubber. Another special application of it is masking unpleasant odors emitting from shoe, floor polisher, and leather as well as paint solvents. In addition, it can sometime used as a solvent, especially for electrophilic reagents in the laboratory. The nitrobenzene is mainly manufactured through the nitration of benzene with the mixture of concentrated sulfuric acid, water and nitric acid. However, the reaction process is quite dangerous due to the exothermicity of the reaction.
Nitrobenzene has a single nitro group attached to a benzene ring. It is an oily yellow liquid with an almond-like odor.It is moderately soluble in water (1.9 g/l at 20 °C) and is soluble in alcohol, acetone, ether, and benzene (IARC, 1996). It has an explosive limit of 1.8% by volume in air, representing a fire hazard.
Nitrobenzene is a synthetic, volatile compound produced primarily for use to manufacture aniline. It is also used as a solvent in refining petroleum and lubricating oils, and in production of dyes, synthetic rubber, pesticides, and drugs including acetaminophen and metoclopramide. Small amounts of nitrobenzene are used as a flavoring agent for soaps and as a solvent for shoe dyes (HSDB, 2009; IARC, 1996). Dinitrobenzene isomers (1, 2-, 1, 3-, and 1, 4-) are used in organic synthesis of dyes, pesticides, and industrial solvents. 1,3-Dinitrobenzene and 1,3,5-trinitrobenzene are chemicals found in the production of explosives.
Nitrobenzene and all isomers (1,2-, 1,3-, and 1,4-) of dinitrobenzene can be absorbed by all routes of exposures and may cause irritation in the respiratory tract and skin. 1,3- Dinitrobenzene and 1,3,5-trinitrobenzene are of severe explosive hazard.
https://pubchem.ncbi.nlm.nih.gov/compound/nitrobenzene#section=Top
https://en.wikipedia.org/wiki/Nitrobenzene
Nitrobenzene is a greenish-yellow crystal or yellow oily liquid, and is slightly soluble in water. The primary hazard of nitrobenzene is toxicity; however, it is also combustible. The boiling point is about 410°F, the flash point is 190°F, and the ignition temperature is 900°F. The specific gravity is 1.2, which is heavier than water, and the material will sink to the bottom. The vapor density is 4.3, which is heavier than air. Nitrobenzene is toxic by ingestion, inhalation, and skin absorption, with a TLV of 1 ppm in air. The four-digit UN identification number is 1652. The NFPA 704 designation is health 3, flammability 2, and reactivity 1. Nitrobenzene is a nitro hydrocarbon derivative, but it is not very explosive. The primary uses are as a solvent, an ingredient of metal polishes and shoe polishes, and in the manufacture of aniline.
Aromatic nitro compounds mixed with nitrobenzene are explosives of high
sensitivity and detonation velocities and are spark detonatable).
Nitrobenzene is a pale yellow to dark brown
oily liquid whose odor resembles bitter almonds (or black
paste shoe polish).
Clear, light yellow to brown, oily liquid with an almond-like or shoe polish odor. May darken on
exposure to air. An experimentally determined odor threshold concentration of 4.7 ppbv was
reported by Leonardos et al. (1969). A detection odor threshold concentration of 9.6 mg/m3 (1.9
ppmv) was determined by Katz and Talbert (1930).
Most nitrobenzene (97%) is used in the manufacture of aniline (IARC 1996, HSDB 2009). Miscellaneous uses include the manufacture of benzidine, quinoline, azobenzene, pyroxylin compounds, isocyanates, pesticides, rubber chemicals, pharmaceuticals, and dyes such as nigrosines and magenta. Nitrobenzene is found in soaps and shoe and metal polishes and is used as a solvent for cellulose ester, in modifying esterification of cellulose acetate, and in refining lubricating oils (HSDB 2009). Nitrobenzene also is used as a solvent in petroleum refining and the synthesis of other organic compounds, such as acetaminophen (ATSDR 1990).
Nitrobenzene is an organic compound used a standard for detection and analyses as well as its removal from the environment. The compound’s cytotoxic effects have been studied in a hepatocarcinoma cell line.
For the manufacture of aniline; in soaps, shoe polishes; for refining lubricating oils; manufacture of pyroxylin Compounds.
The primary use of nitrobenzene is in the captive production of aniline, with about 97.5% of nitrobenzene production consumed in this process. The major use of aniline is in the manufacture of polyurethanes. Nitrobenzene is also used as a solvent in petroleum refining, in the manufacture of cellulose ethers and acetate, and in Friedel-Crafts reactions to hold the catalyst in solution. It is also used in the synthesis of other organic compounds including acetaminophen, which is an over-the-counter analgesic commonly known as Tylenol.
Nitrobenzene is used as a flavoring agent, a perfume for soaps and as a solvent for shoe dyes.
A yellow organic oil obtained
by refluxing benzene with a mixture
of concentrated nitric and sulfuric acids.
The reaction is a typical electrophilic substitution
on the benzene ring by the nitryl
cation (NO2+).
ChEBI: A nitroarene consisting of benzene carrying a single nitro substituent. An industrial chemical used widely in the production of aniline.
nitrobenzene: A yellow oily liquid,C6H5NO2; r.d. 1.2; m.p. 6°C; b.p.211°C. It is made by the nitration ofbenzene using a mixture of nitricand sulphuric acids.
Nitrobenzene is produced by the direct nitration of benzene with a mixture of
sulfuric and nitric acids. U.S. capacity for nitrobenzene production is approximately
1.5 billion pounds . The most important use for
nitrobenzene is in the production of aniline. Nearly 98% of the nitrobenzene
produced in the U.S. is converted to aniline.
Nitrobenzene is produced commercially by the exothermic nitration of benzene with fuming nitric acid in the presence of a sulfuric acid catalyst at 50 to 65℃. The crude nitrobenzene is passed through washer-separators to remove residual acid and is then distilled to remove benzene and water.
Very slightly soluble in water.
Aluminum chloride added to Nitrobenzene containing about 5% phenol caused a violent explosion [Chem. Eng. News 31:4915. 1953]. Heating a mixture of Nitrobenzene, flake sodium hydroxide and a little water led to an explosion, discussed in [Bretherick's 5th ed. 1995]. Mixed with oxidants, i.e. dinitrogen tetraoxide, fluorodinitromethane, nitric acid, peroxodisulfuric acid, sodium chlorate, tetranitromethane, uranium perchlorate, etc., forms highly sensitive explosive, [Bretherick 5th ed, 1995]. Heated mixtures of Nitrobenzene and tin(IV) chloride produce exothermic decomposition with gas production [Bretherick, 5th Ed., 1995].
Toxic by ingestion, inhalation, and skin
absorption. Methemoglobinemia. Possible carcinogen.
The routes of entry of nitrobenzene intothe body are the inhalation of its vaporsor absorption of the liquid or the vaporthrough the skin and, to a much lesserextent, ingestion. The target organs are theblood, liver, kidneys, and cardiovascular system. Piotrowski (1967) estimated that in anexposure period of 6 hours to a concentration of 5 mg/m3, 18 mg of nitrobenzene wasabsorbed through the lungs and 7 mg throughthe skin in humans. Furthermore, about 80%of inhaled vapor is retained in the respiratorytract. The dermal absorption rate at this concentration level is reported as 1 mg/h, whilethe subcutaneous absorption of the liquidis between 0.2 and 0.3 mg/cm3/h (ACGIH1986).
The symptoms of acute toxicity are headache, dizziness, nausea, vomiting, and dyspnea. Subacute and chronic exposure cancause anemia. Nitrobenzene effects the conversion of hemoglobin to methemoglobin. Itis metabolized to aminophenols and nitrophenols to about 30%, which are excreted.
Moderate explosion hazard when exposed to heat or flame. Reacts violently with nitric acid, aluminum trichloride plus phenol, aniline plus glycerine, silver perchlorate and nitrogen tetroxide. Avoid aluminum trichloride; aniline; gycerol; sulfuric acid; oxidants; phosphorus pentachloride; potassium; potassium hydroxide. Avoid sunlight, physical damage to container, freezing, and intense heat.
Nitrobenzene is mainly utilized for aniline production. The aniline is used primarily
for the manufacture of 4,4'-methylenebis (phenyl isocyanate) and polymers
thereof (50%). The second largest use of aniline is in the manufacture of chemicals
for rubber production (30%). Dyes and dye intermediates, hydroquinone and drugs
account for about 8% of the aniline produced, while 10% of the aniline is
converted to agricultural products such as pesticides and defoliants (Northcott
1978). It also is used as a solvent for cellulose ethers and an ingredient in polishes
for metals and shoes (HSDB 1988).
Confirmed carcinogen.
Human poison by an unspecified route.
Poison experimentally by subcutaneous and
intravenous routes. Moderately toxic by
ingestion, skin contact, and intraperitoneal
routes. Human systemic effects by ingestion:
general anesthetic, respiratory stimulation,
and vascular changes. An experimental
teratogen. Experimental reproductive
effects. Mutation data reported. An eye and
skin irritant. Can cause cyanosis due to
formation of methemoglobin. It is absorbed
rapidly through the skin. The vapors are
hazardous.
to heat and flame. Moderate explosion
hazard when exposed to heat or flame.
Explosive reaction with solid or
concentrated alkali + heat (e.g., sodium
hydroxide or potassium hydroxide),
aluminum chloride + phenol (at 12O°C),
aniline + glycerol + sulfuric acid, nitric +
sulfuric acid + heat. Forms explosive
mixtures with aluminum chloride, oxidants
(e.g., fluorodinitromethane, uranium
perchlorate, tetranitromethane, sodium
chlorate, nitric acid, nitric acid + water,
peroxodsulfuric acid, dinitrogen
tetraoxide), phosphorus pentachloride,
potassium, sulfuric acid. Reacts violently
with aniline + glycerin, N20, AgCLO4. To
fight fne, use water, foam, CO2, dry
chemical. Incompatible with potassium
hydroxide. When heated to decomposition it
emits toxic fumes of NOx. See also NITRO
COMPOUNDS OF AROMATIC
HYDROCARBONS.
Nitrobenzene is used in the manufacture
of explosives and aniline dyes and as solvent and intermediate.
It is also used in floor polishes; leather dressings
and polished; and paint solvents, and to mask other
unpleasant odors. Substitution reactions with nitrobenzene
are used to form m-derivatives. Pregnant women may be
especially at risk with respect to nitrobenzene as with many
other chemical compounds, due to transplacental passage
of the agent. Individuals with glucose-6-phosphate dehydrogenase
deficiency may also be special risk groups.
Additionally, because alcohol ingestion or chronic alcoholism
can lower the lethal or toxic dose of nitrobenzene,
individuals consuming alcoholic beverages may be at risk.
Nitrobenzene is reasonably anticipated to be a human carcinogenbased on sufficient evidence of carcinogenicity from studies in experimental animals.
Biological. In activated sludge, 0.4% of the applied nitrobenzene mineralized to carbon dioxide
after 5 d (Freitag et al., 1985). Under anaerobic conditions using a sewage inoculum, nitrobenzene
degraded to aniline (Hallas and Alexander, 1983). When nitrobenzene (5 and 10 mg/L) was
statically incubated in the dark at 25 °C with yeast extract and settled domestic wastewater
inoculum, complete biodegradation with rapid acclimation was observed after 7 to 14 d (Tabak et
al., 1981). In activated sludge inoculum, 98.0% COD removal was achieved in 5 d. The average
rate of biodegradation was 14.0 mg COD/gh (Pitter, 1976).
Razo-Flores et al. (1999) studied the fate of nitrobenzene (50 mg/L) in an upward-flow
anaerobic sludge bed reactor containing a mixture of volatile fatty acids and/or glucose as electron
donors. The nitrobenzene loading rate and hydraulic retention time for this experiment were 43
mg/Ld and 28 h, respectively. Nitrobenzene was effectively reduced (>99.9%) to aniline (92%
molar yield) in stoichiometric amounts for the 100-d experiment.
Photolytic. Irradiation of nitrobenzene in the vapor phase produced nitrosobenzene and 4-
nitrophenol (HSDB, 1989). Titanium dioxide suspended in an aqueous solution and irradiated with
UV light (λ = 365 nm) converted nitrobenzene to carbon dioxide at a significant rate (Matthews,
1986). A carbon dioxide yield of 6.7% was achieved when nitrobenzene adsorbed on silica gel
was irradiated with light (λ >290 nm) for 17 h (Freitag et al., 1985).
Chemical/Physical. In an aqueous solution, nitrobenzene (100 μM) reacted with Fenton’s
reagent (35 μM). After 15 min, 2-, 3-, and 4-nitrophenol were identified as products. After 6 h,
about 50% of the nitrobenzene was destroyed. The pH of the solution decreased due to the
formation of nitric acid (Lipczynska-Kochany, 1991). Augusti et al. (1998) conducted kinetic
studies for the reaction of nitrobenzene (0.2 mM) and other monocyclic aromatics with Fenton’s
reagent (8 mM hydrogen peroxide; [Fe+2] = 0.1 mM) at 25 °C. They reported a reaction rate
constant of 0.0260/min.
Nitrobenzene vapor is readily absorbed through the skin and lungs. At an airborne
nitrobenzene concentration of 10 mg/m3 humans may absorb 18 to 25 mg in 6 h
through the lungs and from 8 to 19 mg
through the skin in the same length of time
.
Urine is the major route of excretion of nitrobenzene metabolites in rabbits
, rats
and mice . The most abundant metabolite in earlier studies in
rabbits and rats was p-aminophenol. This compound, or its glucuronide or sulfate
conjugates, accounted for 19% to 31% of the
dose. In a later study in rats in which the acid hydrolysis step employed by earlier
workers to cleave conjugates was replaced by enzyme hydrolysis, no p-aminophenol
was found in the urine of male Fischer-344 or CD rats .
About 9% of a nitrobenzene dose was excreted by B6C3F1 mice as the sulfate
conjugate. The major metabolites found in Fischer-344 rat urine were p-hydroxyacetanilide
sulfate (19% of the dose), p-nitrophenol sulfate (20% of the dose) and
m-nitrophenol sulfate (10% of the dose) .
In addition, an unidentified metabolite accounted for about 10% of the dose
.
Male CD rats excreted the same metabolites after an oral dose of nitrobenzene,
but in slightly different proportions. They excreted about half
as much of the dose as the glucuronide or sulfate conjugates of P-hydroxyacetanilide
(9% of the dose) and P-nitrophenol (13% of the dose), approximately the
same amount of m-nitrophenol (8% of the dose), and about twice as much as the
unidentified metabolite. Interestingly, whereas Fischer-344 rats excreted the phenolic
metabolites of nitrobenzene exclusively as sulfates, CD rats excreted the
same metabolites in the free form (15-17% of the total metabolite) and as
glucuronides (4-20% of the total metabolite).
Approximately 4% of the dose also was excreted as p-hydroxyacetanilide by
B6C3F1 mice and as p- and m-nitrophenol (7% and 6% of the dose, respectively)
sulfates, glucuronides and free metabolites .
Clearly, ring hydroxylation and reduction are important metabolic steps in the
biotransformation of nitrobenzene in rabbits, rats, mice and humans .
Since no significant isotope effect was found in the metabolism of deuterated
nitrobenzene to these products in rats in vivo , the o- and
p-nitrophenols may be formed through an arene oxide intermediate. A significant isotope effect was noted in the formation of m-nitrophenol from deuterated
nitrobenzene in the same rats, leading to the conclusion that m-nitrophenol is
formed by a direct oxygen insertion mechanism or by some other mechanism
which does not involve an arene oxide intermediate. The reduction of nitrobenzene
in vivo is largely, if not exclusively, due to the action of anaerobic intestinal
microflora. Treatment with antibiotics totally eliminated the ability of cecal
contents of Fischer-344 rats to reduce nitrobenzene in vitro, and rats treated with
antibiotics eliminated p-hydroxyacetanilide as 0.9% of an oral dose of nitro-benzene. Normal rats excreted 16.2% of an oral dose of nitrobenzene as that
metabolite .
The reduction of most nitro compounds by hepatic microsomes is not detectable
under aerobic conditions, but is readily observable under anaerobic conditions.
Mason and Holtzman proposed that the first intermediate in the microsomal
reduction of nitroaromatic compounds is the nitro anion radical, the product
of a one electron transfer to nitrobenzene or other nitroaromatic compound.
Oxygen would rapidly oxidize the radical to yield the parent nitro compound and
Superoxide anion. Both the nitro anion radical and Superoxide anion are potentially
toxic compounds.
Both P-nitrophenol and P-aminophenol have been detected in human urine after
exposure to nitrobenzene. p-Aminophenol has been found only after large accidental
exposures and acid hydrolysis of
urine. Since acid conditions convert p-acetamidophenol to P-aminophenol, the identity of the metabolite actually excreted is in doubt. P-Nitrophenol
has been found in the urine of volunteers exposed to low inhalation doses of
nitrobenzene, and Kuzelova and Popler have suggested that urinary P-nitrophenol
be used to monitor exposure to nitrobenzene.
UN1662 Nitrobenzene, Hazard Class: 6.1;
Labels: 6.1-Poisonous materials.
Common impurities include nitrotoluene, dinitrothiophene, dinitrobenzene and aniline. Most impurities can be removed by steam distillation in the presence of dilute H2SO4, followed by drying with CaCl2, and shaking with, then distilling at low pressure from BaO, P2O5, AlCl3 or activated alumina. It can also be purified by fractional crystallisation from absolute EtOH (by refrigeration). Another purification process includes extraction with aqueous 2M NaOH, then water, dilute HCl, and water, followed by drying (CaCl2, MgSO4 or CaSO4) and fractional distillation under reduced pressure. The pure material is stored in a brown bottle, in contact with silica gel or CaH2. It is very hygroscopic. [Beilstein 5 H 233, 5 I 124, 5 II 171, 5 III 591, 5 IV 708.]
The intermediates and products of nitrobenzene reduction
can cause methemoglobinemia (a condition in which the
blood’s ability to carry oxygen is reduced) by accelerating the
oxidation of hemoglobin to methemoglobin. Three primary
metabolic mechanisms have been identified: reduction of
nitrobenzene to aniline by intestinal microflora, its reduction
to aniline occurring in hepatic microsomes and erythrocytes,
and nitrobenzene oxidative metabolism to the nitrophenols
by hepatic microsomes. Many of the toxicological effects are
likely triggered by metabolites of nitrobenzene. For example,
methemoglobinemia is caused by the interaction of hemoglobin
with the products of nitrobenzene reduction (i.e.,
nitrosobenzene, phenylhydroxylamine, and aniline). The
anaerobic metabolism occurring in the gastrointestinal track is
much faster than reduction by the hepatic microsomal fraction;
therefore, the action of bacteria normally present in the
small intestine is an important element in the formation of
methemoglobin.
Concentrated nitric acid, nitrogen tetroxide;
caustics; phosphorus pentachloride; chemically-active
metals, such as tin or zinc. Violent reaction with strong oxidizers
and reducing agents. Attacks many plastics. Forms
thermally unstable compounds with many organic and inorganic
compounds.
The current initial threshold screening level (ITSL) for nitrobenzene is 0.9 μg/m3 based on an annual averaging time.
Incineration (982℃, 2.0 seconds
minimum) with scrubbing for nitrogen oxides abatement
. Consult with environmental regulatory agencies
for guidance on acceptable disposal practices. Generators
of waste containing this contaminant (≥100 kg/mo) must
conform with EPA regulations governing storage, transportation,
treatment, and waste disposal.
