Хлоруксусной кислоты

Описание

Chloroacetic acid (CAA) is a monohalogenated acetic acid (m-HAA) that is used as a photosensitizing agent and in industrial synthesis of certain organic chemicals such as indigoid dyes. The m-HAAs are a major class of drinking water disinfection by-products during chlorination of drinking water.

Химические свойства

Chloroacetic acid is a colorless to white crystalline solid. It has a strong vinegar-like odor and an Odor Threshold of 0.15 milligram per cubic meter.

Использование

Chloroacetic acid behaves as a very strong monobasic acid and is used as a strong acid catalyst for diverse reactions. The Cl function can be displaced in base-catalyzed reactions.

Определение

A colorless crystalline solid made by substituting one of the hydrogen atoms of the methyl group of ethanoic acid with chlorine, using red phosphorus. It is a stronger acid than ethanoic acid because of the electron-withdrawing effect of the chlorine atom. Dichloroethanoic acid (dichloroacetic acid, CHCl₂COOH) and trichloroethanoic acid (trichloroacetic acid,CCl₃COOH) are made in the same way. The acid strength increases with the number of chlorine atoms present.

Методы производства

Chloroacetic acid can be synthesized by the radical chlorination of acetic acid, treatment of trichloroethylene with concentrated H2SO4, oxidation of 1,2-dichloroethane or chloroacetaldehyde, amine displacement from glycine, or chlorination of ketene.

Общее описание

Chloroacetic acid, solution is a colorless solution of the white crystalline solid. The acid concentration can be up to 80%.It is used in manufacturing dyes and in medicine. Chloroacetic acid is toxic by inhalation, ingestion and skin contact. Chloroacetic acid is corrosive to metals and tissue. Chloroacetic acid is used as an herbicide, preservative and bacteriostat.

Реакции воздуха и воды

Water soluble.

Опасность

Use in foods prohibited by FDA. Irritating and corrosive to skin. Upper respiratory tract irritant. Questionable carcinogen.

Угроза здоровью

Inhalation causes mucous membrane irritation. Contact with liquid causes severe irritation and burns of the eyes and irritation and burns of skin. Ingestion causes burns of mouth and stomach.

Пожароопасность

Special Hazards of Combustion Products: Toxic gases, such as hydrogen chloride, phosgene and carbon monoxide, may be generated.

Профиль безопасности

Poison by ingestion, inhalation, subcutaneous, and intravenous routes. A corrosive skin, eye, and mucous membrane irritant. Questionable carcinogen with experimental tumorigenic data. Mutation data reported. Combustible liquid when exposed to heat or flame. To fight fire, use water spray, fog, mist, dry chemical, foam. When heated to decomposition it emits toxic fumes of Cl-. See also CHLORIDES.

Возможный контакт

This haloacetic acid can be a byproduct of drinking water disinfection and may increase the risk of cancer. Monochloracetic acid is used primarily as a chemical intermediate in the synthesis of sodium carboxymethyl cellulose; and such other diverse substances as ethyl chloroacetate, glycine, synthetic caffeine, sarcosine, thioglycolic acid, and various dyes. Hence, workers in these areas are affected. It is also used as an herbicide. Therefore, formulators and applicators of such herbicides are affected.

Экологическая судьба

CCA by inhibition of the pyruvate-dehydrogenase, aconitase, and a-ketoglutarate dehydrogenase that contribute in tricarboxylic acid cycle and also inhibition of glyceraldehyde- 3-phosphate dehydrogenase can impair production of cellular energy and conversion to anaerobic glycolysis, resulting in increasing acidosis with accumulation of glycolic acid, oxalate, and lactate production. CCA can also affect cellular components via sulfhydryl groups. Both of these effects may contribute to central nervous system (CNS), cardiovascular, renal, and hepatic effects. The metabolites glycolic acid and oxalate may contribute to CNS and renal toxicity (myoglobin and oxalate precipitation in the tubuli). Binding of calcium to oxalates probably causes the hypocalcemia, but hypocalcemia can be secondary to rhabdomyolysis. CAA by reduction of cellular glutathione can cause oxidative stress. Inhibition of mitochondrial aconitase causes hypoglycemia.

Перевозки

UN1750 (liquid) & UN1751 (solid) Chloroacetic acid, solid or liquid, Hazard class: 6.1; Labels: 6.1-Poison Inhalation Hazard, 8-Corrosive material.

Методы очистки

Crystallise the acid from CHCl3, CCl4, *benzene or water. Dry it over P2O5 or conc H2SO4 in a vacuum desiccator. Further purification is by distillation from MgSO4, and by fractional crystallisation from the melt. Store it under vacuum or under dry N2. [Bernasconi et al. J Am Chem Soc 107 3621 1985, Beilstein 2 IV 474.]

Несовместимости

Compounds of the carboxyl group react with all bases, both inorganic and organic (i.e., amines) releasing substantial heat, water, and a salt that may be harmful. Incompatible with arsenic compounds (releases hydrogen cyanide gas), diazo compounds, dithiocarbamates, isocyanates, mercaptans, nitrides, sulfides (releasing heat, toxic, and possibly flammable gases), thiosulfates, and dithionites (releasing hydrogen sulfate and oxides of sulfur). The solution in water is a strong acid. Contact with strong oxidizers, strong bases; and strong reducing agents such as hydrides can cause violent reactions. Chloracetic acid decomposes on heating, producing toxic and corrosive hydrogen chloride, phosgene, and carbon monoxide gases. Attacks metals in the presence of moisture.

Утилизация отходов

Incineration, preferably after mixing with another combustible fuel; care must be exercised to assure complete combustion to prevent the formation of phosgene; an acid scrubber is necessary to remove the halo acids produced.