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Do the solvolysis reactions of secondary substrates occur by the SN1 or SN2 mechanism: or something else?

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Abstract

Primary and methyl aliphatic halides and tosylates undergo substitution reactions with nucleophiles in one step by the classic SN2 mechanism, which is characterized by second-order kinetics and inversion of configuration at the reaction center. Tertiary aliphatic halides and tosylates undergo substitution reactions with nucleophiles in two (or more) steps by the classic SN1 mechanism, which is characterized by first-order kinetics and incomplete inversion of configuration at the reaction center due to the presence of ion pairs. When the nucleophile is also the solvent, the substitution reaction is called a solvolysis, and both the SN2 and SN1 reactions now obey first-order kinetics. Schleyer and Bentley have provided solid, but not conclusive, evidence that secondary substrates undergo solvolysis by a merged mechanism, one that blends characteristics of both the SN2 and SN1 mechanisms. The following paper presents the history of their sustained pursuit of a merged mechanism and subsequent rebuttals to this claim. Several issues related to the philosophy and sociology of science are also discussed.

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References

  • Abenson, P.H.: Trends in scientific research. Science 143(3603), 218–223 (1964)

    Article  Google Scholar 

  • Allen, A.D., Ambidge, I.C., Tidwell, T.T.: Stereochemistry of trifluoroacetolysis of optically active 2-Butyl Tosylate. A test for hydrogen bridging. J. Org. Chem. 48, 4527–4530 (1983)

    Article  Google Scholar 

  • Allen, A.D., Kanagasabapathy, V.M., Tidwell, T.T.: Solvolysis of 1-Arylethyl Tosylates. Kinetic and stereochemical tests for solvent participation. J. Am. Chem. Soc. 107, 4513–4519 (1985)

    Article  Google Scholar 

  • Anslyn, E.V., Dougherty, D.A.: Modern physical organic chemistry. University Science Books, Sausalito, CA (2006)

    Google Scholar 

  • Bentley, T.W., Bowen, C.T., Morten, D.H., Schleyer, P., Von, R.: The SN2-SN1 Spectrum. 3. Solvolyses of secondary and tertiary alkyl sulfonates in fluorinated alcohols. Further evidence for the SN2 (Intermediate) mechanism. J. Am. Chem. Soc. 103, 5466–5475 (1981)

    Article  Google Scholar 

  • Bentley, T.W., Carter, G.E.: The SN2-SN1 Spectrum. 4. The SN2 (Intermediate) mechanism of tert-Butyl Chloride: A revised Y scale of solvent ionizing power based on solvolysis of 1-Adamantyl Chloride. J. Am. Chem. Soc. 104, 5741–5747 (1982)

    Article  Google Scholar 

  • Bentley, T.W., Schleyer, P., Von, R.: The SN2-SN1 Spectrum. 1. Role of nucleophilic solvent assistance and nucleophilically solvated ion pair intermediates in solvolyses of primary and secondary Arenesulfonates. J. Am. Chem. Soc. 98, 7658–7666 (1976)

    Article  Google Scholar 

  • Bentley, T.W., Schleyer, P., Von, R.: Medium effects on the rates and mechanisms of solvolytic reactions. In: Gold, V., Bethell, D. (eds.) Advances in physical organic chemistry, vol. 14, pp. 1–67. Academic Press, New York (1977)

    Google Scholar 

  • Biale, G., Parker, A.J., Smith, S.G., Stevens, I.D.R., Winstein, S.: E2C mechanism in elimination reactions. Absence of an extreme form of merged mechanism for elimination and substitution. Comparison of Saytzeff versus Hofmann Tendencies and of Anti versus Syn Elimination. J. Am. Chem. Soc. 92, 115–122 (1970)

    Article  Google Scholar 

  • Bunting, J.W.: Merged mechanisms for hydride transfer from 1, 4-Dihydronicotinamides. Biorg. Chem. 19, 456–491 (1991)

    Article  Google Scholar 

  • Crane, D.: Fashions in science—Does it exist? Soc. Prob. 16, 433–441 (1969)

    Article  Google Scholar 

  • Dannenberg, J.J., Goldberg, B.J., Barton, J.K., Dill, K., Weinwurzel, D.H., Longas, M.O.: The 2-Butyl Cation in Trifluoroacetic Acid. A hydrogen-bridged carbonium ion. J. Am. Chem. Soc. 103, 7764–7768 (1981)

    Article  Google Scholar 

  • Diaz, A.F., Lazdins, L., Winstein, S.: Oxygen-18 scrambling in solvolyses of simple unactivated alkyl Arenesulfonates. J. Am. Chem. Soc. 90, 1904–1905 (1968)

    Article  Google Scholar 

  • Eliel, E.L., Ro, R.S.: Example of merged bimolecular substitution and elimination. Tetrahedron 2, 353–354 (1958)

    Article  Google Scholar 

  • Fainberg, A.H., Winstein, S.: Correlation of solvolysis data. III. t-Butyl Chloride in a wide range of solvent mixtures. J. Am. Chem. Soc. 78, 2770–2777 (1956)

    Article  Google Scholar 

  • Grunwald, E., Winstein, S.: The correlation of solvolysis rates. J. Am. Chem. Soc. 70, 846–854 (1948)

    Article  Google Scholar 

  • Guthrie, R.D., Jencks, W.P.: IUPAC recommendations for the representation of reaction mechanims. Acc. Chem. Res. 22, 343–349 (1989)

    Article  Google Scholar 

  • Hagstrom, W.O.: Production of culture in science. Am. Behav. Scie. 19, 753–768 (1976)

    Article  Google Scholar 

  • Hammett, L.P.: The effect of structure on the reactions of organic compounds. Benzene derivatives. J. Am. Chem. Soc. 59, 96–103 (1937)

    Article  Google Scholar 

  • Hoffmann, R., Minkin, V.I., Carpenter, B.K.: Ockham’s Razor and chemistry. Bull. Chim. Soc. Fr. 133, 117–130 (1996)

    Google Scholar 

  • Hoffmann, R., Minkin, V.I., Carpenter, B.K.: Ockham’s Razor and chemistry. HYLE 3, 3–28 (1997)

    Google Scholar 

  • Katritzky, A.R.: The mechanisms of nucleophilic substitution in aliphatic compounds. Chem. Soc. Rev. 19, 83–105 (1990)

    Article  Google Scholar 

  • McLennan, D.J.: A neutral nucleophilic probe of borderline kinetic in the 2-Octyl Mesylate-Urea Reaction. Tetrahedron Lett. 16, 4689–4692 (1975)

    Article  Google Scholar 

  • Milton Harris, J., Raber, D.J., Hall, R.E., Schleyer, P., Von, R.: Solvent assistance in the solvolysis of secondary substrates. The use of added Azide Ion as a mechanistic probe. J. Am. Chem. Soc. 92, 5729–5731 (1970)

    Article  Google Scholar 

  • Milton Harris, J., Hall, R.E., Schleyer, P., Von, R.: The magnitude of secondary α-Deuterium isotope effects for limiting solvolses. J. Am. Chem. Soc. 93, 2551–2553 (1971)

    Article  Google Scholar 

  • Okuno, Y.: A cluster model of ion pair formation of t-BuCl in aqueous solution: calculations evidence for nucleophilic solvent assistance in SN1 Reaction. J. Phys. Chem. A 103, 190–196 (1999)

    Article  Google Scholar 

  • Paradisi, C., Bunnett, J.F.: Strong dependence of the incidence of internal return during sovolysis of sec-Alkyl Benzenesulfonates on the structure of the alkyl group. J. Am. Chem. Soc. 103, 946–948 (1981)

    Article  Google Scholar 

  • Reichardt, C.: Solvents and solvent effects in organic chemistry (3rd ed.). Wiley-VCH. Weinheim, Germany (2003)

    Google Scholar 

  • Richard, J.P., Jencks, W.P.: Concerted Bimolecular Substitution Reactions of 1-Phenylethyl Derivatives. J. Am. Chem. Soc. 106, 1383–1396 (1984)

    Article  Google Scholar 

  • San Filippo Jr, J., Romano, L.J.: A convenient preparation of optically active 2-Halooctanes and related compound. J. Org. Chem. 40, 1514–1515 (1975)

    Article  Google Scholar 

  • Schadt, F.L., Schleyer, P., von, R., Bentley, T.W.: Hexafluoroisopropanol—a solvent of high ionizing power and low nucleophilicity. Tetrahedron Lett. 15, 2335–2338 (1974)

    Article  Google Scholar 

  • Schadt, F.L., Bentley, T.W., Schleyer, P., von, R.: The SN2-SN1 Spectrum. 2. Quantitative treatments of nucleophilic solvent assistance. A scale of solvent nucleophilcities. J. Am. Chem. Soc. 98, 7667–7674 (1976)

    Article  Google Scholar 

  • Schleyer, P., Von, R.: A simple preparation of Adamantane. J. Am Chem. Soc. 79, 3292 (1957)

    Google Scholar 

  • Schleyer, P., Von, R., Nichols, R.D.: The preparation and reactivity of 2-substituted derivatives of Adamantane. J. Am. Chem. Soc. 83, 182–187 (1961)

    Google Scholar 

  • Shiner Jr., V.J., Fisher, P., Dowd, W.: Enhancement of solvolysis rates by Wagner-Meerwein rearrangements of ion pairs. J. Am. Chem. Soc. 91, 7748–7749 (1969)

    Article  Google Scholar 

  • Sneen, R.A., Larsen, J.W.: Identification of an ion-pair intermediate in an SN2 reaction. J. Am. Chem. Soc. 88, 2593–2594 (1966)

    Article  Google Scholar 

  • Sneen, R.A., Larsen, J.W.: Substitution at a saturated carbon. X. Unification of mechanisms for SN1 or SN2. J. Am. Chem. Soc. 91, 362–366 (1969)

    Article  Google Scholar 

  • Sober, E.: Simplicity. In a companion to the philosophy of science (Newton-Smith, W. H. ed.). Blackwell, Malden, MA (2001), pp 433–441

  • Streitwieser, A.: Solvolytic displacement reactions. McGraw-Hill, New York (1962)

    Google Scholar 

  • Ziman, J.M.: The problem of “Problem Choice”. Minerva 25, 92–106 (1987)

    Article  Google Scholar 

Download references

Acknowledgments

The author thanks Mark Goodwin, Michael Weisberg and Jeffrey Kovac for their advice and encouragement about this paper.

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Correspondence to Richard M. Pagni.

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Pagni, R.M. Do the solvolysis reactions of secondary substrates occur by the SN1 or SN2 mechanism: or something else?. Found Chem 13, 131–143 (2011). https://doi.org/10.1007/s10698-011-9111-3

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