Functional group trees/parameters

Now the computer must identify the best rate estimation parameters for the forward reaction. First the radical site in the first reactant, ethyl radical, will be classified as primary alkyl using the functional group tree shown in Fig. 8. 

The functional group tree classification of reaction rate parameters is conceptually related to an extension of the thermochemical group-additivity to transition states. In conventional transition state theory, for ideal gases and neglecting tunneling and recrossings, the reaction rate coefficient is given by ... 

In the database we only need to store high-pressure-limit (i.e. thermally-equilibrated intermediates) rate estimation parameters for elementary-step reactions from this information, the molecular structure, and the thermochemical parameters (Section II.D.l) one can compute the pressure-dependent reaction rates. The elementary-step high-pressure-limit rate estimation parameters depend primarily on the local functional group structure, and so are very well-suited to functional group tree classification. 

I. Hierarchical Tree Structure for Functional Group Parameters... 

In the classical free statistics, the number of the functional groups on the surface of a tree-like cluster is of the same order of that of the groups inside the cluster, so that a simple thermodynamic limit without surface term is impossible to take. The equilibrium statistical mechanics for the polycondensation was refined by Yan [14] to treat surface correction in such finite systems. He found the same result as Ziff and Stell. Thus the treatment of the postgel regime is not unique. The rigorous treatment of the problem requires at least one additional parameter defining relative probability of occurrence of infra- and intermolecular reactions in the gel. 

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