Effect of Alpha Inclusion in Kappas

To illustrate briefly the information in the alpha-modified kappa values, is used as an example. Table 5 shows the values for several molecules. The butyl halides in the list reveal the influence of the covalent radius on the shape modeled by the a parameter on the value. As expected, in bromo-butane is the largest, paralleling a shape that is less star graph-like than the other two halides. The same trends are noted in the cyclic molecules in Table 5. 

The algorithms for and do not distinguish which atom or atoms are to be modified by A -h a within the molecule. The insertion of an A + a designated atom anywhere within a molecule leads to the same calculated or values. The inference is that the shape attribute encoded by or indexes is the same regardless of the position(s) of the non-C(sp ) atom(s).  

To illustrate this point, in Table 6 the graph is shown that represents the all C(sp ) molecule l-methyl-4-isopropyl cyclohexane. For this molecule, the value of a = 0 is used when calculating k. The structure is now modified by inserting at various positions a non-C(sp ) atom, X, which has a value of a = 1.0. The choice of a here is the equivalent of inserting an additional C(sp ) atom into the original structure. 

The values of k and are the same for each isomer depicted in columns 1 and 2 of Table 6. The result is that the shapes of all molecules described by the same or the same are the same, regardless of where the actual modified atom is. This is not true in the case of the calculated values. For this index, the a modification of A used in calculating a value may lead 

---