Utente:Grasso Luigi/sanbox1/Nitriti alchilici
I nitriti alchilici sono un gruppo di composti chimici basati sulla struttura molecolare R-ONO. Formalmente sono esteri alchilici dell'acido nitroso. Sono diversi dai nitrocomposti (R-NO2).
I primi cinque membri della serie sono liquidi volatili; il nitrito di metile e il nitrito di etile sono gassosi a pressione e temperatura ambiente. Tali composti hanno un odore distintivo di frutta. Un'altro nitrito molto conosciuto è il nitrito di amile (nome IUPAC: 3-metilbutil nitrito).
I nitriti alchilici erano inizialmente, e in gran parte ancora usati come farmaci e reagenti chimici, una pratica che è iniziata nel tardo 19esimo secolo. Nell'uso della medicina, sono spesso inalati per il sollievo dall'angina e altri sintomi cardiaci della malattia. Tuttavia, quando indicati come "poppers", i nitriti alchilici rappresentano droghe ricreative.
Sintesi e proprieta[modifica | modifica wikitesto]
Organic nitrites are prepared from alcohols and sodium nitrite in sulfuric acid solution. They decompose slowly on standing, the decomposition products being oxides of nitrogen, water, the alcohol, and polymerization products of the aldehyde.[2] They are also prone to undergo homolytic cleavage to form alkyl radicals, the nitrite C-O bond being very weak (on the order of 40-50 kcal mol−1).
Reazioni[modifica | modifica wikitesto]
- tert-Butyl nitrite has been shown to be an effective reagent for the selective nitration of phenols [3] and aryl sulfonamides [4]
- n-Butyl nitrite and ammonia convert phenylhydroxylamine to its nitrosamine derivative cupferron.[5] Likewise pyrrolidine is a substrate for ethyl nitrite.[6]
- Alkyl nitrites are also used in the formation of oximes with the stronger carbon acids and acid or base catalysis for example in the reaction of 2-butanone, ethyl nitrite and hydrochloric acid forming the oxime,[7] the similar reaction with phenacyl chloride,[8] or the reaction of phenylacetonitrile with methyl nitrite and sodium hydroxide.[9]
An isolated but classic example of the use of alkyl nitrites can be found in Woodward and Doering's quinine total synthesis:[10]
for which they proposed this reaction mechanism:
Uso medico[modifica | modifica wikitesto]
Antidoto all'avvelenamento da cianuro[modifica | modifica wikitesto]
Amyl nitrite is used medically as an antidote to cyanide poisoning,[11] The light alkyl nitrites cause the formation of methemoglobin wherein, as an effective antidote to cyanide poisoning, the methemoglobin combines with the cyanide to form nontoxic cyanmethemoglobin.[senza fonte] First responders typically carry a cyanide poison kit containing amyl nitrite.
Note[modifica | modifica wikitesto]
- ^ Development of a rational scale to assess the harm of drugs of potential misuse., in Lancet, vol. 369, n. 9566, 24 March 2007, pp. 1047–53, DOI:10.1016/s0140-6736(07)60464-4.
- ^ n-butyl nitrite Organic Syntheses, Coll. Vol. 2, p.108 (1943); Vol. 16, p.7 (1936). http://www.orgsynth.org/orgsyn/prep.asp?prep=cv2p0108 Link
- ^ Chemoselective Nitration of Phenols with tert-Butyl Nitrite in Solution and on Solid Support Organic Letters, Coll. Vol 11, p.4172-4175 (2009)
- ^ Chemoselective Nitration of Aromatic Sulfonamides with tert-Butyl Nitrite Chemical Communications, DOI: 10.1039/C2CC37481A
- ^ Cupferron Organic Syntheses, Coll. Vol. 1, p.177 (1941); Vol. 4, p.19 (1925) Link
- ^ 2-Pyrrolidinemethanol, α,α-diphenyl-, (±)- Organic Syntheses, Coll. Vol. 6, p.542 (1988); Vol. 58, p.113 (1978) Link
- ^ Dimethylglyoxime Organic Syntheses, Coll. Vol. 2, p.204 (1943); Vol. 10, p.22 (1930) Link
- ^ Glyoxylyl chloride, phenyl-, oxime Organic Syntheses, Coll. Vol. 3, p.191 (1955); Vol. 24, p.25 (1944) Link
- ^ [Benzeneacetonitrile, α-(1,1-dimethylethoxy)carbonylcarbonyl]oxy]imino]-] Organic Syntheses, Coll. Vol. 6, p.199 (1988); Vol. 59, p.95 (1979) Link
- ^ The Total Synthesis of Quinine R. B. Woodward and W. E. Doering J. Am. Chem. Soc.; 1945; 67(5) pp 860 - 874; DOI: 10.1021/ja01221a051
- ^ Amyl Nitrite, in Medsafe, New Zealand Medicines and Medical Devices Safety Authority, 18 maggio 2000. URL consultato il 15 marzo 2007 (archiviato dall'url originale l'11 novembre 2006).