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nitrite

 
Dictionary: ni·trite   (nī'trīt') pronunciation
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n.
The univalent radical NO2 or a compound containing it, such as a salt or an ester of nitrous acid.


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Chemistry Dictionary: nitrite
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A salt or ester of nitrous acid. The salts contain the dioxonitrate (III) ion, NO2 −, which has a bond angle of 115°.


Britannica Concise Encyclopedia: nitrite
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Any salt or ester of nitrous acid (HNO2). The salts are inorganic compounds with ionic bonds, containing the nitrite ion (NO2-) and any cation. The esters are organic compounds with covalent bonds, having the structure R-O-N-O, in which R represents a carbon-containing combining group and the bonding is from carbon to oxygen. These covalent nitrites are constitutional isomers (see isomerism) of the nitro compounds, nitric acid derivatives (R-NO2), in which the bonding is from carbon to nitrogen. Nitrites are used as food preservatives and color enhancers, though they are so toxic they have caused deaths and combine with amines to produce carcinogens. They are used in medicine to dilate blood vessels.

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Food and Nutrition: nitrites
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Found in many plant foods, since they are rapidly formed by the reduction of naturally occurring nitrate. Nitrite is the essential agent in preserving meat by pickling, since it inhibits the growth of clostridia; it also combines with the myoglobin of meat to form the characteristic red nitrosomyoglobin. See also nitrosamines.

Veterinary Dictionary: nitrite
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Any salt of nitrous acid; organic nitrites are used in the treatment of angina pectoris in humans.

  • n. poisoning — causes methemoglobinemia and anemic anoxia. Signs are dyspnea and coffee color of mucosae and blood. Pregnant cows may abort several weeks later. Nitrite may come preformed in feed contaminated by a chemical agent, or in nitrate-rich food in which the nitrate is converted to nitrite during processing, e.g. low temperature cooking, heating of hay in a stack or moldering. Most cases are in ruminants which convert nitrate to nitrite in the rumen, the source being nitrate-rich plants. See also nitrate.
  • n.-treated fish meal — used as a preservative and color-preservation agent the nitrite is converted biologically to a toxic nitrosamine, dimethylnitrosamine.
Wikipedia: Nitrite
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A resonance hybrid, showing the N-O bonds in the nitrite ion have a bond order of about 1.5, leaving most of the single negative charge shared between the terminal oxygen atoms
Space-filling model of NO2−

The nitrite ion is NO2−. The anion is bent, being isoelectronic with ozone. More generally, a nitrite compound is either a salt or an 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.

The two canonical structures of NO2− which contribute to the resonance hybrid shown at the top of the article

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.[1]

Nitrite can be reduced to nitric oxide or ammonia by many species of bacteria.

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 nitrites

Structure of the nitrosooxy functional group

In 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. Nitro compounds share the formula RNO2, but in these compounds the R group attaches to the nitrogen rather than oxygen. 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[2][3][4][5][6][7][8] in which alkyl halides react with metallic nitrites to a mixture to nitroalkanes and nitrites.

External links

References

  1. ^ V. M. Ivanov (2004). "The 125th Anniversary of the Griess Reagent". Journal of Analytical Chemistry 59 (10): 1002 – 1005. doi:10.1023/B:JANC.0000043920.77446.d7.  Translated from V. M. Ivanov (2004). Zhurnal Analiticheskoi Khimii 59 (10): 1109 – 1112. 
  2. ^ Victor Meyer (1872). "Ueber die Nitroverbindungen der Fettreihe". Justus Liebig's Annalen der Chemie 171 (1): 1–56. doi:10.1002/jlac.18741710102. 
  3. ^ Victor Meyer, J. Locher (1876). "Ueber die Pseudonitrole, die Isomeren der Nitrolsäuren". Justus Liebig's Annalen der Chemie 180 (1-2): 133–155. doi:10.1002/jlac.18761800113. 
  4. ^ V. Meyer and Stüber (1872). "Vorläufige Mittheilung". Chemische Berichte 5: 203–205. doi:10.1002/cber.18720050165. 
  5. ^ Victor Meyer, O. Stüber (1872). "Ueber die Nitroverbindungen der Fettreihe". Chemische Berichte 5: 399. doi:10.1002/cber.187200501121. 
  6. ^ Victor Meyer, A. Rilliet (1872). "Ueber die Nitroverbindungen der Fettreiche. Dritte Mittheilung". Chemische Berichte 5: 1029–1034. doi:10.1002/cber.187200502133. 
  7. ^ Victor Meyer, C. Chojnacki (1872). "Ueber die Nitroverbindungen der Fettreihe. Vierte Mittheilung". Chemische Berichte 5: 1034–1038. doi:10.1002/cber.187200502134. 
  8. ^ Robert B. Reynolds, Homer Adkins (1929). "The Relationship of the Constitution of Certain Alky Halides to the Formation of Nitroparaffins and Alkyl Nitrites". Journal of the American Chemical Society 51 (1): 279–287. doi:10.1021/ja01376a037. 

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Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.  Read more
Chemistry Dictionary. A Dictionary of Chemistry. Sixth Edition. Copyright © Market House Books Ltd, 2008. All rights reserved.  Read more
Britannica Concise Encyclopedia. Britannica Concise Encyclopedia. © 2006 Encyclopædia Britannica, Inc. All rights reserved.  Read more
Food and Nutrition. A Dictionary of Food and Nutrition. Copyright © 1995, 2003, 2005 by A. E. Bender and D. A. Bender. All rights reserved.  Read more
Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved.  Read more
Wikipedia. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article "Nitrite".  Read more