210820-71-6Relevant articles and documents
Nitroso group transfer from substituted N-methyl-N-nitrosobenzenesulfonamides to amines. Intrinsic and apparent reactivity
Garcia-Rio,Leis,Moreira,Norberto
, p. 381 - 390 (2001)
We have studied the nitroso group transfer from substituted N-methyl-N-nitrosobenzenesulfonamides to primary and secondary amines, observing that the rate of the reaction increases as a consequence of the presence of electron withdrawing groups on the aromatic ring of the nitrosating agents. The rate constants determined for the nitroso group transfer ktr, give good Bronsted-type relationships between log ktr (rate constant for nitroso group transfer) and pKa/R2NH2+ and pKa/leaving group. The study of the nitrosation processes of secondary amines catalyzed by ONSCN and denitrosation catalyzed by SCN-, in combination with the formation equilibrium of ONSCN, has enabled us to calculate the value of the equilibrium constant for the loss of the NO+ group from a protonated N-nitrosamine (pKNO/R2N+ HNO), which can be defined by analogy with pKa/R2NH2+. The value of pKNO/X-NO for the loss of the NO+ group from an N-methyl-N-nitrosobenzenesulfonamide was obtained in a similar way. By using values of ΔpKNO = pKNO/R2N+ HNO - pKNO/X-NO, we were able to calculate the equilibrium constant for the nitroso group transfer and characterize the transition state. On the basis of Bronsted-type correlations, we have obtained values of βnucl/norm and αlg/norm ? 0.55, showing a perfectly balanced transition state. In terms, of the Marcus theory, the calculation of the intrinsic barriers for the nitroso group transfer reaction shows that the presence of electron withdrawing groups on thearomatic ring of the N-methyl-N-nitrosobenzenesulfonamides does not cause these barriers to vary.
Nitrosation and denitrosation of substituted N-methylbenzenesulfonamides. Evidence of an imbalanced concerted mechanism
Garcia-Rio, Luis,Leis, J. Ramon,Moreira, Jose A.,Norberto, Fatima
, p. 1613 - 1620 (1998)
The kinetics of the nitrosation reaction of several substituted sulfonamides and of the denitrosation of the resulting products have been studied. The denitrosation rate is first-order with respect to both the nitroso compound and acid concentration and no effect of added nucleophiles was observed. The denitrosation reaction is general-acid catalysed, with a Bronsted parameter αd, of 0.7, which is independent of the substituents on the aromatic ring. Kinetic solvent isotope effects range from kH3O+d/ kD3O+d = 1.20 ± 0.05 to 2.04 ± 0.06 for denitrosation by L3O+ and from kAHd/kADd = 1.5 ± 0.2 to 2.3 ± 0.3 for denitrosation by dichloroacetic acid, which suggest that a rate-determining proton transfer is involved in this reaction. For nitrosation reaction, the absence of catalysis by nucleophilic anions, the observed general-base catalysis (βNO = 0.3) and the substituent effects suggest a concerted nitrosation-denitrosation process. The Leffler parameters obtained for N ... H bond formation (αnuc = 0.7) as well as for N ... N=O bond breaking (αlg = 0.17) are in favour of an imbalance in the transition state (αimbalance = 0.53) with the development of a positive charge on the nitrogen adjacent to the nitroso group.
Stability and nitrosation efficiency of substituted N-methyl-N-nitrosobenzenesulfonamides
Garcia-Rio,Leis,Moreira,Norberto
, p. 756 - 760 (2007/10/03)
A series of substituted N-methyl-N-nitrosobenzenesulfonamides [2,4,6-(CH3)3, 4-CH3O, 4-CH3 4-Cl and 4-NO2] were synthesized. All of them transfer their nitroso group to N-methylaniline in a quantitative manner, the more reactive being those substituted with electron-withdrawing groups, thus resembling some of the known alkyl nitrites. Studies of their acid denitrosation and base-catalysed hydrolysis demonstrated that the nitrosobenzenesulfonamides are fairly stable in aqueous media between pH 2 and 11. Their relative stability in aqueous media together with their ability to transfer the nitroso group to nucleophiles suggest their use as excellent alternatives to alkyl nitrites in both neutral and basic media.
