nitrite n : the radical -NO2 or any compound containing it (such as a salt or ester of nitrous acid)
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In inorganic chemistry, nitrites are salts of nitrous acid (HNO2). They contain the nitrite ion (NO2−). Nitrites of the alkali and alkaline earth metals can be synthesized by reacting a mixture of nitrogen monoxide (NO) and nitrogen dioxide (NO2) with a corresponding metal hydroxide solution, as well as through the thermal decomposition of the corresponding nitrate. Other nitrites are available through the reduction of the corresponding nitrates.
Sodium nitrite is used for the curing of meat because it prevents bacterial growth and, in a reaction with the meat's myoglobin, gives the product a desirable dark red color. Because of the toxicity of nitrite (the lethal dose of nitrite for humans is about 22 mg per kg body weight), the maximum allowed nitrite concentration in meat products is 200 ppm. Under certain conditions, especially during cooking, nitrites in meat can react with degradation products of amino acids, forming nitrosamines, which are known carcinogens.
Nitrite is detected and analyzed by the Griess Reaction, involving the formation of a deep red-colored azo dye upon treatment of a NO2−-containing sample with sulfanilic acid and naphthyl-1-amine in the presence of acid.
Under hypoxic conditions, nitrite may release nitric oxide, which causes potent vasodilation. Several mechanisms for nitrite conversion to NO have been described including enzymatic reduction by xanthine oxidoreductase, the mitochondria, and NO synthase (NOS), as well as nonenzymatic acidic disproportionation.
Organic nitritesIn organic chemistry, nitrites are esters of nitrous acid and contain the nitrosooxy functional group. They possess the general formula RONO, where R is an aryl or alkyl group. Amyl nitrite is used in medicine for the treatment of heart diseases.
Nitrites should not be confused with nitrates, the salts of nitric acid, or with nitro compounds, though they share the formula RNO2. The nitrite anion NO2− should not be confused with the nitronium cation NO2+.
A classic named reaction for the synthesis of alkyl nitrites is the Meyer synthesis in which alkyl halides react with metallic nitrites to a mixture to nitroalkanes and nitrites.
- ATSDR - Case Studies in Environmental Medicine - Nitrate/Nitrite Toxicity U.S. Department of Health and Human Services (public domain)
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