Abstract
Electron redistribution is the cornerstone of our understanding of chemical reactivity. For the vast majority of organic reactions electrons are assumed to move in pairs providing explanatory mechanisms through the generation of intermediate structures. But for many transformations these discrete steps are idealized constructs, involving intermediates assumed but not empirically justified. This unitary perspective predicated on the curved arrow formalism has resulted in the scenario where for many organic transformations our supposed understanding far surpasses our growing knowledge. Reformulating organic mechanisms to include single electron transfer (SET) as a component of, or an alternative to, the prevailing iconic descriptions can provide for a more empirically adequate mechanistic description. In addition using the language of SET presents an opportunity to unify mechanistic concepts under a common donor/acceptor framework.
This is a preview of subscription content, log in via an institution to check access.
Notes
The Beilstein database of Organic reactions has logged yearly growth of ca. 250,000 structures, 200,000 reactions and about 40,000 citations from 1979, and as of 2004 contained 9,293,250 chemical reactions (Fialkowski et al. 2005).
It was Ingold’s original intent that the electronic effects used to establish the link between structure and energy be separate from those used to connect structure and reactivity. By the time of his 1934 review (Ingold 1934) the through bond inductive effect and the conjugative mesomeric effect had been classified as permanent, what are termed today as polarization effects. However during the course of a reaction time-independent polarization is replaced by time-dependent polarizability, or what Ingold at the time called the inductomeric and electromeric effects. Today the latter terms are no longer used, and mesomerism has been widely replaced by resonance, where \(\chi_{i}\) is a canonical resonance form, \(\chi_{i} = \prod\nolimits_{j} {n_{j} } \varphi_{j}\), of the wave function, \(\Psi = \sum\nolimits_{i}^{{}} {} c_{i} \chi_{i}\) (Healy 2011).
The succeeding 20 pages presented what H.C. Brown characterized as “an elaborate system of notation” designed to unify a slew of reactions of bases/nucleophiles/reductants with acids/electrophiles/oxidants under a single donor–acceptor framework. The result, as feared by Mulliken himself, was “excessively” elaborate and never widely adopted.
References
Ashby, E.C.: Single-electron transfer, a major reaction pathway in organic chemistry. An answer to recent criticisms. Acc. Chem. Res. 11, 414–421 (1988)
Cooper, M.M., Klymkowsky, M.W.: Comment on “should organic chemistry be taught as science?”. J. Chem. Educ. 97, 1213–1214 (2020)
Esteves, P.M., de Walkimar, J., Carneiro, M., Cardoso, S.P., Barbosa, A.G.H., Laali, K.K., Rasul, G., Surya Prakash, G.K., Olah, G.A.: Unified mechanistic concept of electrophilic aromatic nitration: convergence of computational results and experimental data. J. Am. Chem. Soc. 125, 4836–4849 (2003)
Farcasiu, D.: The use and misuse of the Hammond postulate. J. Chem. Educ. 52, 76 (1975)
Fialkowski, M., Bishop, K.J., Chubukov, V.A., Campbell, C.J., Grzybowski, B.A.: Architecture and evolution of organic chemistry. Angew. Chem. Int. Ed. Engl. 44, 7263–7269 (2005)
Galloway, K.R., Stoyanovich, C., Flynn, A.B.: Students’ interpretations of mechanistic language in organic chemistry before learning reactions. Chem. Educ. Res. Pract. 18, 353–374 (2017)
Gwaltney, S.R., Rosokha, S.V., Head-Gordon, M., Kochi, J.K.: Charge-transfer mechanism for electrophilic aromatic nitration and nitrosation via the convergence of (ab initio) molecular-orbital and Marcus–Hush theories with experiments. J. Am. Chem. Soc. 125, 3273–3283 (2003)
Hammond, G.S.: A correlation of reaction rates. J. Am. Chem. Soc. 77, 334–338 (1955)
Healy, E.F.: Heisenberg’s chemical legacy: resonance and the chemical bond. Found. Chem. 13, 39–49 (2011)
Healy, E.F.: Should organic chemistry be taught as science? J. Chem. Educ. 96, 2069–2071 (2019)
Ingold, C.K.: Principles of an electronic theory of organic reactions. Chem. Rev. 15, 225–274 (1934)
Jencks, W.P.: When is an intermediate not an intermediate? Enforced mechanisms of general acid–base, catalyzed, carbocation, carbanion, and ligand exchange reaction. Acc. Chem. Res. 13, 161–169 (1980)
Kochi, J.K.: Electron transfer and charge transfer: twin themes in unifying the mechanisms of organic and organometallic reactions. Angew. Chem. Int. Ed. Engl. 10, 1227–1266 (1988)
Laszlo, P.: Describing reactivity with structural formulas, or when push comes to shove. Chem. Educ. Res. Pract. 3, 113–118 (2002)
Lopp, I.G., Buhler, J.D., Ashby, E.C.: Organometallic reaction mechanisms. XIII. Identification of the ketyl intermediates formed in reactions of Grignard reagents with ketones. J. Am. Chem. Soc. 107, 4966–4970 (1975)
Mulliken, R.S.: Molecular compounds and their spectra. III. The interaction of electron donors and acceptors. J. Phys. Chem. 56, 801–822 (1952)
Pearson, R.G.: Electronegativity scales. Acc. Chem. Res. 23, 1–2 (1990)
Peltzer, R.M., Gauss, J., Eisenstein, O., Cascella, M.: The Grignard reaction—unravelling a chemical puzzle. J. Am. Chem. Soc. 142, 2984–2994 (2020)
Pross, A.: The single electron shift as a fundamental process in organic chemistry: the relationship between polar and electron-transfer pathways. Acc. Chem. Res. 7, 212–219 (1985)
Savéant, J.M.: Single electron transfer and nucleophilic substitution. Adv. Phys. Org. Chem. Acad. Press 26, 1–130 (1990)
Sutcliffe, B.T.: The development of the idea of a chemical bond. Int. J. Quantum Chem. 58, 645–655 (1996)
Taube, H.: Electron transfer between metal complexes—a retrospective view (Nobel lecture). Angew. Chem. Int. Ed. Engl. 5, 329–339 (1984)
van Fraassen, B.C.: Science as representation: flouting the criteria. Philos. Sci. 71, 794–804 (2004)
van Frassen, B.C.: The Scientific Image. Clarendon, Oxford (1980)
Vasilyev, A.V., Lindeman, S.V., Kochi, J.K.: Molecular structures of the metastable charge-transfer complexes of benzene (and toluene) with bromine as the pre-reactive intermediates in electrophilic aromatic bromination. New J. Chem. 26, 582–592 (2002)
Weiss, J.: Simple electron transfer processes in systems of conjugated double bonds. Trans. Faraday Soc. 42, 116 (1946)
Wiberg, K.B., Rablen, P.R.: Comparison of atomic charges derived via different procedures. J. Comput. Chem. 14, 1504–1518 (1993)
Wöhler, F.: Letter to J.J. Berzelius (28 Jan 1835). In: Bulletin of the Atomic Scientists (Nov 1949), p. 310
Woolley, R.G.: Is there a quantum definition of a molecule? J. Math. Chem. 23, 3 (1998)
Yamazaki, S., Yamabe, S.: A computational study on addition of Grignard reagents to carbonyl compounds. J. Org. Chem. 26, 9346–9353 (2002)
Acknowledgements
The author wishes to acknowledge the Welch Foundation (Grant # BH-0018) for its continuing support of the Chemistry Department at St. Edward’s University.
Author information
Authors and Affiliations
Corresponding author
Additional information
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
About this article
Cite this article
Healy, E.F. Organic chemistry as representation. Found Chem 23, 59–68 (2021). https://doi.org/10.1007/s10698-020-09379-z
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10698-020-09379-z