Computational methods pathway stability

Several theoretical studies of diazirinyl radicals have been undertaken. Multiconfiguration self-consistent field (MCSCF) calculations have been used to investigate the stability of, and isomerization between, the diazirinyl anion 6 and the open-chain biradical anion 7 (Scheme 1) <1995JPC6548>. Dimerization of aryldiazirinyl radicals has been explored by computational and experimental methods <2004PCCP756>. Both approaches support the predominance of the N-N dimer 9 over the isomeric C-N form 8. Furthermore, bimolecular dimer decomposition was shown to be considerably more favorable than the alternative unimolecular pathways. 

Computational methodology has been used to accompany or to anticipate experimental results for many classes of compounds. Such results are particularly helpful for transient species, for rationalization of physical and structural properties, and for simulation of reaction pathways and transition states. Semiempirical valence electron (CNDO/MNDO), ab initio, and nonquantum mechanical force field (molecular mechanics) calculations have mainly been used for the examination of structure and stability of moderately strained olefins, whereas many-electron quantum-chemical methods have been used for detailed discussion of electronic aspects. Excellent reviews of molecular mechanics calculations, the principal method used to describe geometrical and energy features in distorted double bond systems, have been written by Osawa and Musso (61). 

The overwhelming success of using theoretical methods to predict and explain experimental results has encouraged and stimulated the application of computers to new areas of research in zeolite chemistry. The capability of current computational techniques used in zeolite studies includes molecular modelling of the framework structure, simulation of X-ray diffraction data, predictions of the physical and chemical properties of zeolite crystals, their stability at different temperatures and pressures leading to prediction of new structures, the adsorption and diffusion of sorbed molecules, calculating vibrational properties of sorbed and sorbent molecules and predicting the reaction pathways in catalytic reactions. 

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