Huckel INDEX

Slater-type orbitals were introduced in Section 5.2 (Eq. (5.2)) as the basis functions used in extended Huckel theory. As noted in that discussion, STOs have a number of attractive features primarily associated with the degree to which they closely resemble hydrogenic atomic orbitals. In ab initio HF theory, however, they suffer from a fairly significant limitation. There is no analytical solution available for the general four-index integral (Eq. 

Various reactivity indices have been derived for benzenoid hydrocarbons from the following purely topological approaches the Huckel model (HMO), first-order perturbation theory (PMO), the free electron MO model (FEMO), and valence-bond structure resonance theory (VBSRT). Since many of the indices that have been known for a long time (index of free valence Fr, self-atom polarizability ir , superdelocalizability Sr, Brown s index Z, cation localization energy Lr+, Dewar reactivity number Nt, Brown s para-localization energy Lp) have been described in detail by Streitwieser in his well-known volume [23] we will refer here only to some more recent developments. 

Figure 2 Comparison of measured mean ionic activity coefficients with those predicted by the Debye-Huckel limiting law. (Data from Handbook of Chemistry and Physics, 77th ed. A James, M Lord. VNR Index of Chemical Physical Data. New York Van Nostrand Reinhold, 1992.

In equations 3-S, a is the anion-cation close-approach distant, B and C are the Dd ye-Huckel parameters at 0.1 MPa, n is the refractive index of the solvent, and the other symbols have the usual SI meanings. Thus, theory predicts that AF can be equated approximately with AF r Since the pressure dependences of both n and D are closely linked to that of the density p of the solvent, i.e., to P, it follows that A is determined in large part by the compressibility of the solvent. Sample calculations for model 3+/2+ couples are given in Table 1. 

Neely, White, and Rudzik have applied the Huckel molecular orbital technique to estimate the different electronic parameters in attempting to deduce which index correlates with the analgesic activity of a series of imidazolines. 

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