Нитробензол

Описание

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.

Химические свойства

Nitrobenzene is a pale yellow to dark brown oily liquid whose odor resembles bitter almonds (or black paste shoe polish).

Физические свойства

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 ppb_v 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).

Использование

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.

Определение

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.

Методы производства

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.

Подготовка

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.

Реакции воздуха и воды

Very slightly soluble in water.

Профиль реактивности

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].

Опасность

Toxic by ingestion, inhalation, and skin absorption. Methemoglobinemia. Possible carcinogen.

Угроза здоровью

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.

Пожароопасность

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.

Промышленное использование

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).

Профиль безопасности

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.

Возможный контакт

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.

Канцерогенность

Nitrobenzene is reasonably anticipated to be a human carcinogenbased on sufficient evidence of carcinogenicity from studies in experimental animals.

Перевозки

UN1662 Nitrobenzene, Hazard Class: 6.1; Labels: 6.1-Poisonous materials.

Методы очистки

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.]

Несовместимости

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.

Утилизация отходов

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.