Pauling-Wheland resonance

The NRT resonance weights, bond orders, and valencies are generally comparable to those of the older Pauling-Wheland theory (particularly for species of low ionicity) and can be used to rationalize chemical phenomena in a similar fashion. Pauling s classic, The Nature of the Chemical Bond, brilliantly illustrates such reasoning. 

Figure 5.10 shows the relation [749] between the 13C chemical shifts and the 7r-electron density calculated by Fernandez-Alonso [765] using the Pauling-Wheland method for the heterocyclic moieties of the purine and pyrimidine nucleosides. Only the resonances of the 13C —H atoms obey the Spiesecke-Schneider relation [76] (160 ppm downfield shift... 

One approach to a complete solution of the Pauling-Wheland resonance-theoretic model is to treat it as a quantum-chemical configuration-interaction problem, now defined on a space of reduced size (corresponding only to those VB structures which are Kekule structures). However this space still has a size that often increases exponentially with the size of G. Thence one (ultimately) wishes further simplifications in dealing with the Hamiltonian and overlap matrixes H and S. 

An approriate wavefunction Ansatz simplifies ground-state computations. In analogy to the Pauling-Wheland resonance-theoretic Ansatz of Sect. 5.2, Herndon [71] proposed... 

Pauling, Wheland 1930 Resonance, valence bond theory... 

B. S. Park, Chemical translators Pauling, Wheland and their strategies for teaching the theory of resonance , Brit. J. Hist. Sci., 1999, 32, 21 —4(5. 

G. W. Wheland, Theory of Resonance and Its Application to Organic Chemistry (New York J. Wiley and Sons London Chapman and Hall, 1944). The Pauling-Wheland controversy on the ontological status of resonance is described in the contribution of K. Gavroglu and A. Simoes in this volume. 

Klein DJ, Seitz WA (1988) Pauling-Wheland resonance theory of benzenoid hydrocarbons. J Mol Stmct (Theochem) 169 167-181... 

The number of Kekule stmctures (Kekule structure count, KSC) of a conjugated hydrocarbon gives information on the thermodynamic stability and chemical reactivity and is used for the computation of various structural indices for ben-zenoid hydrocarbons " the Pauling bond order, PBO the stability index SI, SI = KSC the r-electron energy, Kekul6 structures are considered in valence-bond resonance-theoretical models such as the Pauling-Wheland model, the... 

These equations allow one to connect NRT bond order (Fab) with Pauling-Wheland bond order (cab) and the older covalent-ionic resonance concepts. They also allow smooth integration of resonance and valency concepts for organic and inorganic compounds. 

Stork [1963] completely rejects the Russian accusation that resonance theory as developed by Pauling, Wheland, and Ingold fails both empirically and philosophically. However, it should be noted that these criticisms (in the GDR) of the events in Moscow appeared well after the hype was over in the USSR. Furthermore, as Brush [1999, 268] correctly remarks For chemists in the West, the apparent absurdity of the Marxist ideological critique obscured a significant difference between VB and MO. According to Brush the molecular orbital theory permits a more realistic interpretation than the valence bond (or resonance) theory. However that may be, reflection on resonance hybrids, tautomerism, the riddle of benzene, and such like is still a relatively neglected theme in the philosophy of chemistry. 

The matrix elements of the Pauling-Wheland resonance theory between Kekule structures K and K are given as °... 

Pauling, L. Wheland, G.W. The Nature of the Chemical Bond. V. The Quantum-Mechanical Calculation of the Resonance Energy of Benzene and Naphthalene and the Hydrocarbon Free Radicals J. Chem. Phys. 1933, 1, 362-374 Errata, ibid, 1934, 2, 482. 

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