Advanced Quantum Theory of Organic Molecules

Exercise 6-9 Set up atomic-orbital models to represent the hybrid structures of N03 , C032 , and N20. 

Exercise 6-10 Set up an atomic-orbital model of each of the following structures with normal values for the bond angles. Evaluate each model for potential resonance (electron delocalization). If resonance appears to you to be possible, draw a set of reasonable valence-bond structures for each hybrid.  

Exercise 6-11 Draw valence-bond structures for the phenylmethyl radical, C6H5CH2-, 

In recent years, great progress has been made in quantum-mechanical calculations of the properties of small organic molecules by so-called ab initio methods, which means calculations from basic physical theory using only fundamental constants, without calibration from known molecular constants. Calculations that are calibrated by one or more known properties and then used to compute other properties are called semiempirical calculations. 

It should be made clear that there is no single, unique ab initio method. Rather, there is a multitude of approaches, all directed toward obtaining useful approximations to mathematical problems for which no solution in closed form is known or foreseeable. The calculations are formidable, because account must be taken of several factors the attractive forces between the electrons and the nuclei, the interelectronic repulsions between the individual electrons, the internuclear repulsions, and the electron spins. 

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