Nitrosation and denitrosation of substituted N-methylbenzenesulfonamides. Evidence of an imbalanced concerted mechanism

Abstract

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 Brønsted parameter, α_d, of 0.7, which is independent of the substituents on the aromatic ring. Kinetic solvent isotope effects range from k_d^H₃O+/k_d^D₃O+ = 1.20 ± 0.05 to 2.04 ± 0.06 for denitrosation by L₃O⁺ and from k_d^AH/k_d^AD = 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 (β_NO = 0.3) and the substituent effects suggest a concerted nitrosation–denitrosation process. The Leffler parameters obtained for N  · · ·  H bond formation (α_nuc = 0.7) as well as for N  · · ·  N[double bond, length half m-dash]O bond breaking (α_lg = 0.17) are in favour of an imbalance in the transition state (α_imbalance = 0.53) with the development of a positive charge on the nitrogen adjacent to the nitroso group.

References

1. D. L. H. Williams, Nitrosation, Cambridge University Press, UK, 1988.
2. (a) A. Castro, E. Iglesias, J. R. Leis, M. E. Peña and J. Vázquez Tato, J. Chem. Soc., Perkin Trans. 2, 1986, 1725; (b) J. Casado, A. Castro, F. Meijide, M. Mosquera and J. Vázquez Tato, J. Chem. Soc., Perkin Trans. 2, 1987, 1759; (c) C. Bravo, P. Hervés, J. R. Leis and M. E. Peña, J. Chem. Soc., Perkin Trans. 2, 1991, 2091.
3. J. Casado, A. Castro, M. Mosquera, M. F. Rodriguez Prieto and J. Vázquez Tato, Ber. Bunsenges. Phys. Chem., 1983, 87, 1211.
4. G. Hallett and D. L. H. Williams, J. Chem. Soc., Perkin Trans. 2, 1980, 1372.
5. J. Casado, A. Castro, J. R. Leis, M. Mosquera and M. E. Peña, Monatsh. Chem., 1984, 115, 1047.
6. T. H. Black, Aldrichimica Acta, 1983, 16, 3.
7. L. García-Río, J. R. Leis, J. A. Moreira and F. Norberto, J. Phys. Org. Chem., in the press.
8. (a) L. García-Río, E. Iglesias and J. R. Leis, J. Org. Chem., 1997, 62, 4701; (b) L. García-Río, E. Iglesias and J. R. Leis, J. Org. Chem., 1997, 62, 4712.
9. (a) R. Montesano and H. Bartsch, Mutation Res., 1976, 32, 179; (b) A. E. Pegg, Adv. Cancer Res., 1977, 25, 195.
10. (a) Transplacental Carcinogenics, eds. L. Tomatis and U. Mohr, IARC Scientific Publications no. 4, IARC, Lyon, 1973; (b) D. Yarosh, Mutation Res., 1985, 145, 1.
11. D. L. H. Williams, J. Chem. Soc., Perkin Trans. 2, 1976, 1838.
12. E. Iglesias, L. García-Río, J. R. Leis, M. E. Peña and D. L. H. Williams, J. Chem. Soc., Perkin Trans. 2, 1992, 1673.
13. G. Dauphin and A. Kergomard, Bull. Soc. Chim. Fr., 1961, 5, 486.
14. C. N. Berry and B. C. Challis, J. Chem. Soc., Perkin Trans. 2, 1974, 1638.
15. P. Salomaa, L. L. Schaleger and F. A. Long, J. Am. Chem. Soc., 1964, 86, 1.
16. I. D. Biggs and D. L. H. Williams, J. Chem. Soc., Perkin Trans. 2, 1975, 107.
17. L. García-Río, J. R. Leis, J. A. Moreira and F. Norberto, unpublished results.
18. (a) N. S. Bayliss, R. Dingle, D. W. Watts and R. C. Wilkie, Aust. J. Chem., 1963, 16, 933; (b) J. H. Ridd, Adv. Phys. Org. Chem., 1978, 15, 1.
19. B. C. Challis and J. A. Challis, in The Chemistry of Amino, Nitroso and Nitro Compounds and Their Derivatives, ed. S. Patai, Wiley, New York, 1983, ch. 26.
20. R. P. Bell, The Proton in Chemistry, Chapman and Hall, London, 1973.
21. (a) L. Melander and W. H. Saunders, Reaction Rates of Isotopic Molecules, Wiley, New York, 1980; (b) J. Albery, in Proton Transfer Reactions, eds. E. Caldin and V. Gold, Chapman and Hall, London, 1975, p. 263.
22. A. J. Kresge, Pure Appl. Chem., 1964, 8, 243.
23. The magnitude of the isotope effects is similar for hydron transfer from the hydronium ion and from the carboxylic acids, which implies a more symmetrical transition state for the former than for the latter. However experimental data show much more variation in reactivity within the carboxylic acid set than between it and the hydronium ion. As one of the referees suggests this anomaly could be rationalised by considering that isotope effects between electronegative atoms are always secondary with no primary component [see (a)]. Nevertheless the secondary isotope effect of 1.25, which is obtained for denitrosation by carboxylic acid by using the fractionation factors [see (b)], is not consistent with experimental data. We think that the similarity in reactivity between carboxylic acids and the hydronium ion is due to the switch from a neutral to a cationic acid as is reported in the following references. (a) C. G. Swain, D. A. Kuhn and R. L. Schowen, J. Am. Chem. Soc., 1965, 87, 1553; (b) K. B. J. Schowen, in Transition States of Biochemical Processes, eds. R. D. Gandour and R. L. Schowen, Plenum Press, New York, 1978, ch. 6.
24. W. P. Jencks, Chem. Rev., 1972, 72, 705.
25. R. A. More O'Ferrall, J. Chem. Soc. B, 1970, 274.
26. (a) A. Williams, Acc. Chem. Res., 1984, 17, 425; (b) A. Williams, Adv. Phys. Org. Chem., 1992, 27, 1.
27. A. R. Hopkins, R. A. Day and A. Williams, J. Am. Chem. Soc., 1983, 105, 6062.
28. J. Shakes, C. Raymond, D. Rettura and A. Williams, J. Chem. Soc., Perkin Trans. 2, 1996, 1553.
29. (a) C. F. Bernasconi, Tetrahedron, 1985, 41, 3219; (b) C. F. Bernasconi, Acc. Chem. Res., 1987, 20, 301; (c) C. F. Bernasconi, Adv. Phys. Org. Chem., 1992, 27, 119.
30. M. Eigen, Angew. Chem., Int. Ed. Engl., 1964, 3, 1.
31. A. Williams, Chem. Soc. Rev., 1994, 23, 93.