- Reactivity of some products formed by the reaction of sorbic acid with sodium nitrite: Decomposition of 1,4-dinitro-2-methylpyrrole and ethylnitrolic acid
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Sorbic acid reacts with nitrite to yield mutagenic products such as 1,4-dinitro-2-methylpyrrole (NMP) and ethylnitrolic acid (ENA). In order to know the stability of these compounds, a kinetic study of their decomposition reactions was performed in the 6.0-9.5 pH range. The conclusions drawn are as follows: (i) The decomposition of NMP occurs through a nucleophilic attack by OH- ions, with the rate equation as follows: r = kdec NMP[OH-][NMP] with kdecNMP (37.5 °C) = 42 ± 1 M-1 s-1. (ii) The rate law for the decomposition of ENA is as follows: r = kdecENA[ENA] Ka/(Ka + [H+]), with Ka being the ENA dissociation constant and kdecENA (37.5 °C) = (7.11 ± 0.04) × 10-5 s-1. (iii) The activation energies for NMP and ENA decomposition reactions are, respectively, Ea = 94 ± 3 and 94 ± 1 kJ mol-1. (iv) The observed values for the decomposition rate constants of NMP and ENA in the pH range of the stomach lining cells, into which these species can diffuse, are so slow that they could be the slow determining step of the alkylation mechanisms by some of the products resulting from NMP and ENA decomposition. Thus, the current kinetic results are consistent with the low mutagenicity of these species.
- Perez-Prior, M. Teresa,Manso, Jose A.,Gomez-Bombarelli, Rafael,Gonzalez-Perez, Marina,Garcia-Santos, M. Pilar,Calle, Emilio,Caballero, M. Cruz,Casado, Julio
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- Mechanism of Reaction of Isomeric Nitrolic Acids to Nitrile Oxides in Aqueous Solution
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Both E and Z isomers of acetonitrolic acids 15 and 16 can be prepared when the OH group is protected by acetylation.Photoisomerization of the E-isomer resulted in quantitative conversion into the pure Z-isomer 16.Hydrolysis of the E-isomer 15 produced the parent nitrolic acid 14 which undergoes loss of NO2(1-) from the conjugate base at high pH.This reaction is however relatively slow suggesting base solubility and acidic reprecipitation as a method of purification of E-nitrolic acids.Deprotection of (Z)-O-acetylacetonitrolic acid by HO(1-) gives a highly reactive Z-nitrolic acid 17 which undergoes loss of NO2(1-) at a rate which precludes its detection; however the subsequent reactions of acetonitrile oxide (CH3CNO) formed were monitored.Rapid loss of NO2(1-) therefore occurs when there is assistance from an antiperiplanar lone pair on the imino nitrogen of the oximate anion.Arylnitrolic acids were also examined; these were in the E configuration 26 and therefore underwent slow loss of NO2(1-).Since NMR and IR data are unreliable for the assignment of configuration of nitrolic acids (relative to other oximes) a single crystal diffraction study was carried out on E-acetonitrolic acid 14.The large difference in reactivity observed for the E- and Z-nitrolic acids now permits strong supporting evidence for structural assignments.
- Egan, Carmel,Clery, Maurice,Hegarty, Anthony F.,Welch, Alan J.
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p. 249 - 256
(2007/10/02)
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- REACTIONS OF NITRILE OXIDES WITH NITROGEN OXIDES. 1. REACTIONS WITH NITROGEN TETROXIDE
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We have studied the reaction of nitrile oxides with nitrogen tetroxide.It was shown that the reaction is selective: acetonitrile oxide yields ethylnitrolic acid, α-oximinophenylacetonitrile oxide gives a mixture of isomers of phenylnitrofuroxan, and aromatic nitrile oxides give aryltrinitromethanes.
- Rakitin, O. A.,Ogurtsov, V. A.,Godovikova, T. I.,Khmel'nitskii, L. I.
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p. 1469 - 1471
(2007/10/02)
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- Kinetics and Mechanism of the Nitrosation of 2-Nitropropane, 1-Nitropropane, and Nitroethane
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The kinetics of the nitrosation of the nitronic acids derived from 2-nitropropane, 1-nitropropane, and nitroethane, in aqueous perchloric acid using nitrous acid, show a first-order dependence upon the and a curved acidity dependence.The results are readily explained by a mechanism in which nitrosation (by H2NO2(1+) or NO(1+)) occurs initially at an oxygen atom, and releasing a proton.The O-nitroso intermediate, which is formed reversibly, then undergoes an internal O- to C-nitroso group rearrangement to give the nitroso nitro product (pseudonitrole) from the secondary nitro compound, and (after tautomerisation) the nitro oxime product (nitrolic acid) from the primary nitro compounds.Neither the first nor the second step is fully rate-limiting, under the conditions used, but the first step is probably close to the diffusion-controlled limit.The reactions are strongly catalysed by Cl(1-), Br(1-), and SCN(1-), but the measured rate constants show a curved dependence on and , suggesting that the intermediates are formed reversibly.However, the reactions are first-order in , so that reaction now occurs via ClNO, BrNO, and ONSCN at the carbon atom of the nitronic acid.The results are discussed, together with those in the literature which describe nitrosation reaction where different nitrosating agents attack the same molecule at different sites.In all three cases studied a further, much slower reaction occurs, which results in the formation of more of the same products (when 0 0).This reaction which is first-order in and , but is not chloride or bromide ion-catalysed, also occurs when no nitrous acid is added.The product is formed by the slow hydrolysis of the protonated form of the nitronic acid, releasing nitrous acid, which reacts further with the unchanged nitronic acid.
- Iglesias, Emilia,Williams, D. Lyn H.
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p. 1035 - 1040
(2007/10/02)
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- Mutagen Formation in the Reaction of Nitrite with the Food Components Analogous to Sorbic Acid
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Mutagen formation by the reaction of sodium nitrite with some sorbic acid analogs was investigated by using the microbial mutagenicity tests (rec-assay and Ames test) together with chemical examination using TLC, and it became clear that the conjugated dienoic carbonyl structure is essential for mutagen formation by the reaction with nitrite.By a large scale reaction of sodium nitrite with sorbic acid methyl ester, 5-nitro-2,4-hexadienoic acid methyl ester and ethylnitrolic acid were isolated and identified as the main mutagens.The results led to the assumption that a nitro group adjacent to the double bond is an important factor to develop mutagenicity.
- Osawa, Toshihiko,Namiki, Mitsuo
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p. 2299 - 2304
(2007/10/02)
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