Higher-level descriptors in molecular connectivity

The optimal modeling of the lattice enthalpy of metal halides, of the boiling points of the mixed class of alcohols plus amines and of two activities of chlorofluorocarbons, the rates of hydrogen abstraction and the minimum anesthetic concentrations, has been achieved thanks to the introduction of three new types of higher-order terms. The first type of term, the mixed molecular connectivity-pseudoconnectivity term, Z = f(X, Y), is function of the molecular connectivity term, X, and of the molecular pseudoconnectivity term, Y, only. Terms X and Y are function of a basis index β that can be either a molecular connectivity index, Χ, or a molecular pseudoconnectivity index, ψ. The Z term can be found by trying different operational combinations of X and Y terms. The second and third type of mixed higher-order terms, Z' = f (Z, β) and Z' = f (X, Y, β), can be found by the aid of a trial-and-error search procedure in which Z or X and Y terms are held constant throughout the search. Modeled properties show these three types of higher-order mixed terms at work: the two different properties of chlorofluorocarbons are modeled by the aid of a Z = f (X, Y) term, the lattice enthalpy of metal halides is instead modeled by a Z' = f(Z, β) term, and the boiling point of the mixed class alcohols plus amines is modeled by a Z'= f(X, Y, β) term.