- Reactivity of Nucleophilic Nitrogen Compounds towards the Nitroso Group
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We discuss the reactivity of 43 nucleophilic nitrogen compounds towards the nitroso group of N-methyl-N-nitrosotoluene-p-sulfonamide (MNTS), and in some cases with alkyl nitrites.The series of nucleophiles considered is structurally very varied, includes members exhibiting the alpha effect, and covers 8 pKa units and a range of reactivities of almost five orders of magnitude.The values of solvent isotope effects and activation parameters have been measured and throw light on the structure of the transition states involved.Reactivities do not correlate well with thebasicity of the nucleophile, largely owing to the behaviour of primary amines, ammonia and nucleophiles with an alpha effect.Application of the curve crossing model suggests a relationship with vertical ionization potentials.The relationship with Ritchie's N+ scale is discussed, and interesting correlations with the reactivities of the same nucleophiles in various other chemical processes are noted.
- Garcia-Rio, Luis,Iglesias, Emilia,Leis, J. Ramon,Pena, M. Elena,Rios, Ana
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- Formation of Nitrosamines in Alkaline Conditions: a Kinetic Study of the Nitrosation of Linear and Cyclic Secondary Amines by Nitroalkanes
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A study has been made of the nitrosation of sixteen secondary amines, six alkylamines (dimethylamine, diethylamine, dipropylamine, diisopropylamine, dibutylamine, diisobutylamine) and ten cyclic secondary amines (2-methylaziridine, azetidine, pyrrolidine, piperidine, 2-methylpiperidine, homopiperidine, heptamethyleneimine, piperazine, 1-methylpiperazine and morpholine) by nitropropane and nitrobutane in a strongly basic medium (-> = 0.1 mol dm-3).The nitrites were not formed in situ (i.e. in the actual bulk of the reaction medium) but rather were isolated,purified and used in pure form.The rate equation (i) was found v = k2obs (i).The fitting of the experimental results to the Taft correlation points to a nucleophilic attack on nitrite esters by the amines.Analysis of the log k2/pKa and log k2/Ei(v) correlations indicates orbital control of the reactions studied.These results, together with the fact that the reactivity of the different amines diminishes ostensibly when the values of the 13C-H nuclear spin coupling constant in the series of corresponding cycloalkanes increase, show that the overall hybridization of the nitrogen atom in the cycle changes from sp2 in the triangular nucleophile methylaziridine to sp3 in larger cycles.The results obtained at different temperatures and with water-tetrahydrofuran media, together with a study of isotope effects suggest that these reactions occur through a highly ordered transition state and that the role of solvation should not be overlooked.
- Calle, Emilio,Casado, Julio,Cinos, Jose L.,Mateos, Francisco J. Garcia,Tostado, Manuel
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p. 987 - 991
(2007/10/02)
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