- Alkylating potential of N-phenyl-N-nitrosourea
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Alkylating agents are considered to be archetypical carcinogens. Since the decomposition of alkylnitrosoureas gives rise to alkyldiazonium ions without any need for metabolic activation, they offer an ideal series of compounds with which to examine the ef
- Manso,Perez-Prior,Gomez-Bombarelli,Gonzalez-Perez,Cespedes,Garcia-Santos,Callea,Casado
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- Kinetic Study of the Phenylurea-Nitrous Acid Reaction: Evidence for an O-Nitrosation Initial Step
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The kinetics of the reaction between phenylurea (PhU) and nitrous acid in aqueous perchloric acid solution at 25 deg C have been studied spectrophotometrically over the acidity range pH 2.2-4.0 (μ 0.2 mol dm-3) by the initial-rate method and over the range 0.50-3.00 mol dm-3 (μ 2.0 mol dm-3, except for 3.0 mol dm-3) by the integration method.The proposed reaction mechanism for both weakly and strongly acidic media involves the rapid formation of an O-nitroso compound (I) followed by two separate reaction paths, the rate-controlling step in both cases being the loss of a proton by (I).In this step (I) is transformed to either of two conjugate bases, one of which subsequently undergoes rearrangement to secondary N-nitrosophenylurea (PhUNO) and the other to the unstable primary N-nitrosophenylurea, which a series of fast steps converts into benzenediazonium ion (PhN2(1+).These fast steps involve the nitrosating agent, which explains the stoicheiometry of the reaction (: 1:2).The ratio between the formation constants of benzenediazonium ion and N-nitrosophenylurea is 0.3 in the absence of base catalysis.In keeping with the nature of the rate-controlling step, general base catalysis was found to be exerted in weakly acid media by both nitrite ion and the carboxylate anions of the buffers used, but not by halide ions.
- Meijide, Francisco,Tato, Vazquez Jose,Casado, Julio,Castro, Albino,Mosquera, Manuel
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p. 1759 - 1766
(2007/10/02)
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- Conformational Preferences in Alkylnitrosoureas
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The spectroscopic properties of several N-alkyl-N-nitrosoureas, N,N'-dialkyl-N-nitrosoureas, and N,N',N'-trialkyl-N-nitrosoureas have been studied in carbon disulfide and chloroform solutions.The NH stretching frequencies in the IR spectra have been observed in both concentrated and dilute solution and in the presence of added dioxane.The results indicate that there is a strong intramolecular hydrogen bond in the mono- and dialkylnitrosoureas.The chemical shifts and line widths of the NMR spectra have also been studied in these solvents.The large chemical shift differences, about 1.3 ppm, for the NH protons in the monoalkylnitrosoureas and other spectroscopic features in the monoalkyl- and dialkylnitrosoureas also indicate that an intramolecular hydrogen bond contributes to a strong conformational preference.The temperature dependence of the NMR spectra of several N,N',N'-trialkyl-N-nitrosoureas establishes that the energy barrier for rotation about the carbon dialkylamide bond is about 13 kcal mol-1.Dipolar resonance interactions are primarily responsible for this barrier.This interaction is augmented by a strong, 8-10 kcal mol-1, hydrogen bond in the mono- and dialkylnitrosoureas.
- Snyder, John K.,Stock, Leon M.
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p. 886 - 891
(2007/10/02)
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