ПЕНТАХЛОРЭТАН

Химические свойства

colourless liquid with a camphor-like smell.Pentachloroethane is incompatible and very reactive in contact with sodium potassium (alloy + bromoform), alkalis, metals, and water. On hydrolysis, pentachloroethane produces dichloroacetic acid and the reaction with alkalis and metals produces chloroacetylenes, which becomes spontaneously explosive. Pentachloroethane is a colourless stable liquid with a camphor-like smell and non-flammable. Pentachloroethane is incompatible with strong oxidising agents and reacts violently with alkalis or metals.

Физические свойства

Clear, colorless liquid with a sweetish, chloroform-like odor

Использование

Pentachloroethane has been used as a solvent and chemical intermediate but has had little commercial utilization. Pentachloroethane is used as a solvent for oil and grease in metal cleaning; in the separation of cola from impurities by density difference; as a chemical intermediate in the manufacture of tetrachloroethylene and dichloroacetic acid; as a solvent for cellulose acetate, certain cellulose ethers, resins, and gums; as a drying agent for timber by immersion at temperatures greater than 100
C; in dry cleaning and soil sterilizing.

Общее описание

A colorless liquid with a chloroform-like odor. Insoluble in water and denser than water. Toxic by inhalation and ingestion. May irritate skin and eyes. Used as a solvent.

Реакции воздуха и воды

Insoluble in water.

Профиль реактивности

A mixture of PENTACHLOROETHANE with potassium may explode after a short delay. Reaction with alkalis or metals will produce a violent reaction. PENTACHLOROETHANE also reacts violently with NaK alloy + bromoform. PENTACHLOROETHANE is incompatible with strong oxidizing agents.

Угроза здоровью

Irritation of skin, lungs, eyes, and mucous membrane; depression of central nervous system; and toxicity similar to tetrachloroethanes.

Профиль безопасности

Poison by inhalation and intravenous routes. Moderately toxic by ingestion and subcutaneous routes. An irritant. Questionable carcinogen with experimental carcinogenic data. Flammable when exposed to heat or flame. Moderately explosive by spontaneous chemical reaction. To fight fire, use water, CO2, dry chemical. Dehalogenation by reaction with alkalies, metals, etc., wdl produce spontaneously explosive chloroacetylenes. Violent reaction with NaK alloy + bromoform. Mixtures with potassium are very shock-sensitive explosives. When heated to decomposition it emits highly toxic fumes of Cl-. See also CHLORINATED HYDROCARBONS, ALIPHATIC.

Канцерогенность

The NTP performed a carcinogenesis/ general toxicity bioassay with F344/N rats and B6C3F1 mice. Chronic inflammation of the kidney and interstitial inflammation of lung were observed in male rats with a positive dose–response relationship. A Frank effect level of 54 for male rats was observed. NTP concluded that “Under the conditions of this bioassay, technical grade pentachlorethane containing 4.2% hexachlorethane (known carcinogen in mice) was not carcinogenic in F344/N rats. The decreased survival of dosed rats was confounding. Pentachloroethane was nephrotoxic to male rats. Technical grade pentachloroethane was carcinogenic for B6CeF1 mice, causing hepatocellular carcinomas in males and females and adenomas in females. This study was cited by IARC as a limited evidence for the carcinogenicity of pentachloroethane in experimental animals. Combined with the lack of epidemiological data for exposure, IARC stated that pentachloroethane was not classifiable as carcinogenic to humans. There is concern for the possibility of a-2 m-globulin nephropathy occurring. However, considering that the pathological sequence of lesions has not been fully established, this cannot be verified. When fed 5 days/week to male rats for 104 weeks at doses of 75 and 150 mg/kg/day, mortality was excessive and body weight gain was below controls starting at 76 weeks. Weight gain was decreased in female rats at both levels starting at 42 weeks, but mortality in both sexes was increased only at 150 mg/kg/day.No increase in tumors was found, but there was a dose-related increase in the incidence of chronic renal inflammation of male rats and mineralization of renal papillae.
Survival of mice similarly treated with 250–500 mg/kg/ day was significantly shortened, and hepatocellular carcinomas were increased. The only other tumor showing an increase was in female mice, where there was a dose-related increase in hepatocellular adenoma. The cause of death did not appear to be either the renal lesions in male rats or the liver tumors in mice, and no other target organs were found to explain the deaths.

Экологическая судьба

Chemical/Physical. At various pHs, pentachloroethane hydrolyzed to tetrachloroethylene (Jeffers et al., 1989; Roberts and Gschwend, 1991). Dichloroacetic acid was also reported as a hydrolysis product. Reacts with alkalies and metals producing explosive chloroacetylenes (NIOSH, 1997). The reported hydrolysis half-life at 25 °C and pH 7 is 3.6 d (Jeffers et al., 1989).
In anoxic hypolimnion samples collected from Lower Mystic Lake, MA, pentachloroethane was abiotically transformed within days to tetrachloroethylene via dehydrohalogenation pathway and to trichloroethylene via reductive elimination. After 10 d, mass balances of 91 and 86% were reported for unaltered and filter-sterilized samples, respectively. A disappearance rate constant of 0.26/d was reported for pentachloroethane for both the unaltered and filter-sterilized samples. The disappearance of pentachloroethane was abiotic in origin due to the reactions with naturally occurring aqueous polysulfides, H2S and Sn^-2 (Miller et al., 1998a).
The evaporation half-life of pentachloroethane (1 mg/L) from water at 25 °C using a shallowpitch propeller stirrer at 200 rpm at an average depth of 6.5 cm was 46.5 min (Dilling, 1977).

Методы очистки

Usual impurities include trichloroethylene. It partially decomposes if it is distilled at atmospheric pressure. Drying it with CaO, KOH or sodium is unsatisfactory because of the elimination of the elements of HCl. It can be purified by steam distillation, or by washing with conc H2SO4, water, and then aqueous K2CO3, drying with solid K2CO3 or CaSO4, and fractionally distilling under reduced pressure. [Beilstein 2 IV 147.]