Electronic theory organic chemistry

However, by the 1920s, as we have seen, a self-conscious use of electron theory in a dynamical interpretation of the old static chemical molecule recovered dynamical theoretical foundations for organic chemists in what became the disciplinary specialization of physical organic chemistry. The theory of electron valency and organic reaction mechanisms, in particular, the theory of mesomerism, developed as a new theoretical chemistry, a little prior to wave mechanics, along a largely independent track. 

Chemistry as it was realized substantially derives from the interae-tion of electrons. The electronic theory of chemistry, particularly of organic chemistry, emerged, explaining the great richness of chemical observations and transformation, as expressed by Ingold, Robinson, Hammett, and many others following in their footsteps. 

No mechanistic aspects of organic chemistry (or, for this reason, any reaction intermediates) were ever mentioned by Zemplen in his lectures or writings, nor did he consider or accept their existence. I never heard him mention the names of Meerwein, Ingold, Robinson, or any other pioneers of the mechanistic electronic theory of organic chemistry. The possible role of organic ions was similarly never mentioned. He was. 

For the electronic theory of organic chemistry 1926 was the annus mirabilis, and, particularly, as they applied to aromatic substitution, the... 

The electronic theory of organic chemistry, and other developments such as resonance theory, and parallel developments in molecular orbital theory relating to aromatic reactivity have been described frequently. A general discussion here would be superfluous at the appropriate point a brief summary of the ideas used in this book will be given ( 7- )-... 

Robinson, R. (1932). Two Lectures on an Outline of an Electrochemical Electronic) Theory of the Course of Organic Reactions. London Institute of Chemistry. 

THEORIES RELATING STRUCTURE AND REACTIVITY 7.2.1 The electronic theory of organic chemistry... 

This qualitative theory still provides the most widely used means for describing reactions in organic chemistry. Two principal modes of electronic interaction in organic molecules are recognised the inductive and mesomeric effects. 

Theories of molecular stracture attempt to describe the nature of chemical bonding both qualitatively and quantitatively. To be useful to chemists, the bonding theories must provide insight into the properties and reactivity of molecules. The stractural theories and concepts that are most useful in organic chemistry are the subject of this chapter. Our goal is to be able to relate molecular stracture, as depicted by stractural formulas and other types of stractural information, such as bond lengths and electronic distributions, to the chemical reactivity and physical properties of molecules. 

Another broad approach to the description of molecular structure that is of importance in organic chemistry is molecular orbital theory. Molecular orbital (MO) theory pictures electrons as being distributed among a set of molecular orbitals of discrete... 

Dewar, M.J.S. The Electronic Theory of Organic Chemistry Oxford University Press London, 1949 p 52. 

Lamola, A. A. (1969). Electronic energy transfer in solutions theory and application. In Leermakers, P. A., and Weissberger, A. (eds.), Energy Transfer and Organic Photochemistry, Technique of Organic Chemistry 14 17-132. Interscience Publishers, New York. 

The more recent work finds its origin in the developments in theoretical organic chemistry which occurred after 1930. By means of the electronic theory of G. N. Lewis and by the consistent application of the ionic theory and that of equilibria to organic chemistry, C. K. Ingold and others began to classify the many compounds and reactions according to fundamental principles, a process which is well known to have yielded a rich harvest. 

The VB and MO theories are both procedures for constructing approximations to the wavefunctions of electrons, but they construct these approximations in different ways. The language of valence-bond theory, in which the focus is on bonds between pairs of atoms, pervades the whole of organic chemistry, where chemists speak of o- and TT-bonds between particular pairs of atoms, hybridization, and resonance. However, molecular orbital theory, in which the focus is on electrons that spread throughout the nuclear framework and bind the entire collection of atoms together, has been developed far more extensively than valence-bond... 

In the Brpnsted picture, the acid is a proton donor, but in the Lewis picture the proton itself is the acid since it has a vacant orbital. A Brpnsted acid becomes, in the Lewis picture, the compound that gives up the actual acid. The advantage of Lewis theory is that it correlates the behavior of many more processes. For example, AICI3 and BF3 are Lewis acids because they have only 6 electrons in the outer shell and have room for 8. Both SnCU and SO3 have eight, but their central elements, not being in the first row of the periodic table, have room for 10 or 12. Other Lewis acids are simple cations, like Ag. The simple reaction A + B- A—B is not very common in organic chemistry, but the scope of the Lewis picture is much larger because reactions of the types... 

Robinson R (1932) Outline of an electrochemical (electronic) theory of the course of organic reactions. The Institute of Chemistry of Great Britain and Ireland, London... 

Dewar, M. J. S., The Molecular Orbital Theory of Organic Chemistry, McGraw-Hill, New York, 1969 R. G. Pan, The Quantum Theory of Molecular Electronic Structure, Benjamin, New York, 1963. 

Dewar MJS (1945) Nature 156 784 Dewar MJS (1946) J Chem Soc 777 Dewar MJS (1949) The electronic theory of organic chemistry. Oxford Clarendon Press, London Haaland A (1989) Angew Chem 101 1017 Haaland A (1989) Angew Chem Intern Ed Engl 28 992... 

Bettinger, H. F., Schleyer, P. v. R., Schreiner, P. R., Schaefer, III, H. F., 1997, Computational Analyses of Prototype Carbene Structures and Reactions in Modem Electronic Structure Theory and Applications in Organic Chemistry, Davidson, E. R. (ed.), World Scientific, Singapore. 

Other approximate, more empirical methods are the extended Huckel 31> and hybrid-based Hiickel 32. 3> approaches. In these methods the electron repulsion is not taken into account explicitly. These are extensions of the early Huckel molecular orbitals 4> which have successfully been used in the n electron system of planar molecules. On account of the simplest feature of calculation, the Hiickel method has made possible the first quantum mechanical interpretation of the classical electronic theory of organic chemistry and has given a reasonable explanation for the chemical reactivity of sizable conjugated molecules. 

---