Бромоформ

Химические свойства

Bromoform is a colorless to pale yellow liquid with a high refractive index, very high density, and sweetish odor is similar to that of chloroform. It is slightly soluble in water and is nonflammable. Bromoform can form in drinking water as a by-product from the reaction of chlorine with dissolved organic matter and bromide ions.

Физические свойства

Clear, colorless to yellow liquid with a chloroform-like odor. Odor threshold concentration in water is 0.3 mg/kg (Verschueren, 1982).

Определение

ChEBI: Bromoform is a member of bromomethanes and a bromohydrocarbon.

прикладной

In separating mixtures of minerals. Bromoform is used as a fluid for mineral ore separation in geological tests, as a laboratory reagent, and in the electronics industry in quality assurance programs.
Bromoform was formerly used as a solvent for waxes, greases, and oils, as an ingredient in fire-resistant chemicals and in fluid gauges. It was also used in the early part of this century as a medicine to help children with whooping cough get to sleep. Currently, bromoform is only produced in small amounts for use in laboratories and in geological and electronics testing.

Подготовка

Bromoform can be prepared by reacting chloroform (see IAC, 1987) with aluminium tribromide at less th an or equal to 60°C; by reacting ethanol with sodium hypobromite; or by the redistribution reaction between chloroform and ethyl bromide (Harlow & Ross, 1932; Soroos & Hinkamp, 1945; Sherman & Kavasmaneck, 1980).

Общее описание

Bromoform appears as a colorless liquid with a chloroform-like odor. Denser than water (density: 2.9 g / cm3 ) and slightly soluble in water. Hence sinks in water. Nonflammable. Toxic by ingestion, inhalation and skin absorption. A lachrymator. Used as a solvent and to make pharmaceuticals. Often stabilized with 1 to 3% ethanol.

Реакции воздуха и воды

Slightly soluble in water.

Профиль реактивности

Heating Bromoform to decomposition produces highly toxic fumes of carbon oxybromide (carbonyl bromide) and hydrogen bromide [Sax, 9th ed., 1996, p. 519]. Reaction with powdered potassium or sodium hydroxide, Li or Na/K alloys, is violently exothermic [Weizmann, C. et al., J. Am Chem. Soc., 1948, 70, p. 1189]. Explosive reaction with crown ethers in the presence of potassium hydroxide [Le Goaller, R. et al., Synth. Comm., 1982, 12, p. 1163].

Опасность

A questionable carcinogen. By ingestion, inhalation, and skin absorption. Liver damage, eye and upper respiratory tract irritant.

Угроза здоровью

Probable routes of human exposure to bromoform are inhalation, ingestion, and dermal contact.
Harmful if inhaled, swallowed, contacts skin or eyes or is absorbed through skin. It is a lachrymator, respiratory irritant, a narcotic and an hepatotoxin. Prolonged exposure may cause dermatitis. Inhalation causes irritation of nose and throat; provokes the flow of tears and saliva and reddening of the face. Ingestion may cause dizziness, disorientation and slurred speech, unconsciousness and death.
Non-Cancer: Bromoform is a central nervous system depressant, and its vapors are highly irritating to the eyes and respiratory tract. Limited observations in humans and animal studies indicate that acute inhalation or oral exposure to high levels of bromoform may cause liver and kidney injury. Chronic effects of bromoform exposure in humans have not been studied, although animal studies indicate adverse effects on the liver, kidney, and central nervous system (U.S. EPA, 1994a).

Пожароопасность

Behavior in Fire: May decompose to produce toxic gases and vapor such as hydrogen bromide and bromine.

Профиль безопасности

Suspected carcinogen with experimental neoplastigenic data. A human poison by ingestion. Moderately toxic by intraperitoneal and subcutaneous routes. Human mutation data reported. A lachrymator. It can damage the liver to a serious degree and cause death. It has anesthetic properties simdar to those of chloroform, but is not sufficiently volatile for inhalation purposes and is far too toxic for human use. As a sedative and antitussive its medicinal application has resulted in numerous poisonings. Inhalation of small amounts causes irritation, provoking the flow of tears and saliva, and reddening of the face. Abuse can lead to adhction and serious consequences. Explosive reaction with crown ethers or potassium hydroxide. Violent reaction with acetone or bases. Incompatible with Li or NaK alloys. When heated to decomposition it emits hghly toxic fumes of Br-. See also BROMIDES.

Экологическая судьба

Biological. Bromoform showed significant degradation with gradual adaptation in a staticculture flask-screening test (settled domestic wastewater inoculum) conducted at 25 °C. At concentrations of 5 and 10 mg/L, percent losses after 4 wk of incubation were 48 and 35, respectively (Tabak et al., 1981).
Surface Water. Kaczmar et al. (1984) estimated the volatilization half-life of bromoform from rivers and streams to be 65.6 d.
Chemical/Physical. The estimated hydrolysis half-life in water at 25 °C and pH 7 is 686 yr (Mabey and Mill, 1978). Products of hydrolysis include carbon monoxide and hydrobromic acid (Kollig, 1993). When an aqueous solution containing bromoform was purged with hydrogen for 24 h, only 5% of the bromoform reacted to form methane and minor traces of ethane. In the presence of colloidal platinum catalyst, the reaction proceeded at a much faster rate forming the same end products (Wang et al., 1988). In an earlier study, water containing 2,000 ng/μL of bromoform and colloidal platinum catalyst was irradiated with UV light. After 20 h, about 50% of the bromoform had reacted. A duplicate experiment was performed but the concentration of bromoform was increased to 3,000 ng/μL and 0.1 g zinc was added. After 14 h, only 0.1 ng/μL bromoform remained. Anticipated transformation products include methane and bromide ions (Wang and Tan, 1988).
At influent concentrations of 1.0, 0.1, 0.01, and 0.001 mg/L, the adsorption capacities of the GAC used were 19.6, 5.9, 1.8, and 0.52 mg/g, respectively (Dobbs and Cohen, 1980).

Методы очистки

The storage and stability of bromoform and chloroform are similar. Ethanol, added as a stabilizer, is removed by washing with H2O or with saturated CaCl2 solution, and the CHBr3, after drying with CaCl2 or K2CO3, is fractionally distilled. Prior to distillation, CHBr3 has also been washed with conc H2SO4 until the acid layer is no longer coloured, then dilute NaOH or NaHCO3, and H2O. A further purification step is fractional crystallisation by partial freezing. [Beilstein 1 IV 82.]