Nitroso
Inorganic chemistry,nitrosorefers to afunctional groupin which thenitric oxide(−N=O) group is attached to an organicmoiety.As such, various nitroso groups can be categorized asC-nitroso compounds (e.g., nitrosoalkanes;R−N=O),S-nitroso compounds (nitrosothiols;RS−N=O),N-nitroso compounds (e.g.,nitrosamines,RN(−R’)−N=O), andO-nitroso compounds (alkyl nitrites;RO−N=O).
Synthesis
[edit]Nitroso compounds can be prepared by the reduction ofnitro compounds[1]or by the oxidation ofhydroxylamines.[2] Ortho-nitrosophenols may be produced by theBaudisch reaction.In theFischer–Hepp rearrangementaromatic 4-nitrosoanilines are prepared from the correspondingnitrosamines.
Properties
[edit]
Nitrosoarenes typically participate in amonomer–dimer equilibrium.The azobenzeneN,N'-dioxide (Ar(–O)N+=+N(O–)Ar) dimers, which are often pale yellow, are generally favored in the solid state, whereas the deep-green monomers are favored in dilute solution or at higher temperatures. They exist ascisandtransisomers.[4]The central "double bond" in the dimer in fact has a bond order of about 1.5.[5]
When stored inprotic media,primaryandsecondarynitrosoalkanesisomerizetooximes.[6]Some tertiary nitrosoalkanes also isomerize to oximes through C-C bond fission, particularly if the bond iselectron-poor.[7]Nitrosophenols and naphthols isomerize to the oximequinonein solution, but reversibly; nitrosophenol ethers typically dealkylate to facilitate the isomerization. Nitroso tertiary anilines generally do not dealkylate in that way.[8]
Due to the stability of the nitric oxidefree radical,nitroso organyls tend to have very low C–Nbond dissociation energies:nitrosoalkanes have BDEs on the order of 30–40 kcal/mol (130–170 kJ/mol), while nitrosoarenes have BDEs on the order of 50–60 kcal/mol (210–250 kJ/mol). As a consequence, they are generally heat- and light-sensitive. Compounds containing O–(NO) or N–(NO) bonds generally have even lower bond dissociation energies. For instance,N-nitrosodiphenylamine,Ph2N–N=O, has a N–N bond dissociation energy of only 23 kcal/mol (96 kJ/mol).[9]
Organonitroso compounds serve as aligandsgivingtransition metal nitroso complexes.[10]
Reactions
[edit]Many reaction exists which make use of an intermediate nitroso compound, such as theBarton reactionandDavis–Beirut reaction,as well as in the synthesis ofindoles,for example:Baeyer–Emmerling indole synthesis,Bartoli indole synthesis.In theSaville reaction,mercury is used to replace a nitrosyl from a thiol group.
C-nitroso compounds are used in organic synthesis as synthons in some well-documented chemical reactions such as hetero Diels-Alder (HDA), nitroso-ene and nitroso-aldol reactions.[11]
Nitrosyl in inorganic chemistry
[edit]
Nitrosyls are non-organic compounds containing the NO group, for example directly bound to the metal via the N atom, giving a metal–NO moiety. Alternatively, anonmetalexample is the common reagentnitrosyl chloride(Cl−N=O). Nitric oxide is a stableradical,having an unpaired electron. Reduction of nitric oxide gives the nitrosylanion,NO−:
- NO + e−→ NO−
Oxidation of NO yields thenitrosoniumcation,NO+:
- NO → NO++ e−
Nitric oxide can serve as aligandformingmetal nitrosyl complexesor just metal nitrosyls. These complexes can be viewed as adducts ofNO+,NO−,or some intermediate case.
In human health
[edit]Nitrosocompounds react withprimary aminesin acidic environments to formnitrosamines,which human metabolism converts to mutagenicdiazo compounds.Small amounts of nitro and nitroso compounds form during meatcuring;the toxicity of these compoundspreservesthe meat againstbacterial infection.After curing completes, the concentration of these compounds appears to degrade over time. Their presence in finished products has been tightly regulated since several food-poisoning cases in the early 20th century,[12]but consumption of large quantities of processed meats can still cause a slight elevation ingastricandoesophageal cancerrisk today.[13][14][15][16]
For example, during the 1970s, certainNorwegianfarm animals began exhibiting elevated levels ofliver cancer.These animals had been fedherringmealpreserved withsodium nitrite.The sodium nitrite had reacted withdimethylaminein the fish and produceddimethylnitrosamine.[17]
The effects of nitroso compounds vary dramatically across the gastrointestinal tract, and with diet. Nitroso compounds present in stool do not induce nitrosamine formation, because stool has neutralpH.[18][19]Stomach aciddoes cause nitrosamine compound formation, but the process is inhibited when amine concentration is low (e.g. a low-protein diet or no fermented food). The process may also be inhibited in the case of highvitamin C (ascorbic acid)concentration (e.g. high-fruit diet).[20][21][22]However, when 10% of the meal is fat, the effect reverses, and ascorbic acid markedly increases nitrosamine formation.[23][24]
See also
[edit]- Nitrosamine,the functional group with the NO attached to an amine, such as R2N–NO
- Nitrosobenzene
- Nitric oxide
- Nitroxyl
References
[edit]- ^G. H. Coleman; C. M. McCloskey; F. A. Stuart (1945). "Nitrosobenzene".Org. Synth.25:80.doi:10.15227/orgsyn.025.0080.
- ^Calder, A.; Forrester, A. R.; Hepburn, S. P."2-Methyl-2-nitrosopropane and Its Dimer".Organic Syntheses.52:77;Collected Volumes,vol. 6, p. 803.
- ^E.Bosch (2014). "Structural Analysis of Methyl-Substituted Nitrosobenzenes and Nitrosoanisoles".J. Chem. Cryst.98(2): 44.doi:10.1007/s10870-013-0489-8.S2CID95291018.
- ^Beaudoin, D.; Wuest, J. D. (2016). "Dimerization of AromaticC-Nitroso Compounds ".Chemical Reviews.116(1): 258–286.doi:10.1021/cr500520s.PMID26730505.
- ^Williams, D. L. H. (1988).Nitrosation.Cambridge, UK:Cambridge University.p. 36.ISBN0-521-26796-X.
- ^Kirby, G. W. (1977). "Electrophilic C-nitroso-compounds".Chemical Society Reviews.6:2.doi:10.1039/CS9770600001(Tilden lecture).
- ^Williams 1988,p. 36.
- ^Williams 1988,pp. 59–61.
- ^Luo, Yu-Ran (2007).Comprehensive Handbook of Chemical Bond Energies.Boca Raton, FL: Taylor and Francis.ISBN9781420007282.
- ^Lee, Jonghyuk; Chen, Li; West, Ann H.; Richter-Addo, George B. (2002). "Interactions of Organic Nitroso Compounds with Metals".Chemical Reviews.102(4): 1019–1066.doi:10.1021/cr0000731.PMID11942786.
- ^Bianchi, P.; Monbaliu, J. C. M. (2022). "Three decades of unveiling the complex chemistry ofC-nitroso species with computational chemistry ".Organic Chemistry Frontiers.9:223–264.doi:10.1039/d1qo01415c.
- ^Honikel, K. O. (2008)."The use an control of nitrate and nitrite for the processing of meat products"(PDF).Meat Science.78(1–2): 68–76.doi:10.1016/j.meatsci.2007.05.030.PMID22062097.
- ^Lunn, J.C.; Kuhnle, G.; Mai, V.; Frankenfeld, C.; Shuker, D.E.G.; Glen, R. C.; Goodman, J.M.; Pollock, J.R.A.; Bingham, S.A. (2006)."The effect of haem in red and processed meat on the endogenous formation of N-nitroso compounds in the upper gastrointestinal tract".Carcinogenesis.28(3): 685–690.doi:10.1093/carcin/bgl192.PMID17052997.
- ^Bastide, Nadia M.; Pierre, Fabrice H.F.; Corpet, Denis E. (2011)."Heme Iron from Meat and Risk of Colorectal Cancer: A Meta-analysis and a Review of the Mechanisms Involved".Cancer Prevention Research.4(2): 177–184.doi:10.1158/1940-6207.CAPR-10-0113.PMID21209396.S2CID4951579.
- ^Bastide, Nadia M.; Chenni, Fatima; Audebert, Marc; Santarelli, Raphaelle L.; Taché, Sylviane; Naud, Nathalie; Baradat, Maryse; Jouanin, Isabelle; Surya, Reggie; Hobbs, Ditte A.; Kuhnle, Gunter G.; Raymond-Letron, Isabelle; Gueraud, Françoise; Corpet, Denis E.; Pierre, Fabrice H.F. (2015)."A Central Role for Heme Iron in Colon Carcinogenesis Associated with Red Meat Intake".Cancer Research.75(5): 870–879.doi:10.1158/0008-5472.CAN-14-2554.PMID25592152.S2CID13274953.
- ^Jakszyn, P; Gonzalez, CA (2006)."Nitrosamine and related food intake and gastric and oesophageal cancer risk: A systematic review of the epidemiological evidence".World Journal of Gastroenterology.12(27): 4296–4303.doi:10.3748/wjg.v12.i27.4296.PMC4087738.PMID16865769.
- ^Joyce I. Boye; Yves Arcand (2012-01-10).Green Technologies in Food Production and Processing.Springer Science & Business Media. p. 573.ISBN978-1-4614-1586-2.
- ^Lee, L; Archer, MC; Bruce, WR (October 1981). "Absence of volatile nitrosamines in human feces".Cancer Res.41(10): 3992–4.PMID7285009.
- ^Kuhnle, GG; Story, GW; Reda, T; et al. (October 2007). "Diet-induced endogenous formation of nitroso compounds in the GI tract".Free Radic. Biol. Med.43(7): 1040–7.doi:10.1016/j.freeradbiomed.2007.03.011.PMID17761300.
- ^Mirvish, SS; Wallcave, L; Eagen, M; Shubik, P (July 1972). "Ascorbate–nitrite reaction: possible means of blocking the formation of carcinogenicN-nitroso compounds ".Science.177(4043): 65–8.Bibcode:1972Sci...177...65M.doi:10.1126/science.177.4043.65.PMID5041776.S2CID26275960.
- ^Mirvish, SS (October 1986). "Effects of vitamins C and E onN-nitroso compound formation, carcinogenesis, and cancer ".Cancer.58(8 Suppl): 1842–50.doi:10.1002/1097-0142(19861015)58:8+<1842::aid-cncr2820581410>3.0.co;2-#.PMID3756808.S2CID196379002.
- ^Tannenbaum SR, Wishnok JS, Leaf CD (1991)."Inhibition of nitrosamine formation by ascorbic acid".The American Journal of Clinical Nutrition.53(1 Suppl): 247S–250S.Bibcode:1987NYASA.498..354T.doi:10.1111/j.1749-6632.1987.tb23774.x.PMID1985394.S2CID41045030.Retrieved2015-06-06.
Evidence now exists that ascorbic acid is a limiting factor in nitrosation reactions in people.
- ^Combet, E.; Paterson, S; Iijima, K; Winter, J; Mullen, W; Crozier, A; Preston, T; McColl, K. E. (2007)."Fat transforms ascorbic acid from inhibiting to promoting acid-catalysedN-nitrosation ".Gut.56(12): 1678–1684.doi:10.1136/gut.2007.128587.PMC2095705.PMID17785370.
- ^Combet, E; El Mesmari, A; Preston, T; Crozier, A; McColl, K. E. (2010). "Dietary phenolic acids and ascorbic acid: Influence on acid-catalyzed nitrosative chemistry in the presence and absence of lipids".Free Radical Biology and Medicine.48(6): 763–771.doi:10.1016/j.freeradbiomed.2009.12.011.PMID20026204.