The relation between molecular connectivity and gas chromatographic retention data

Benzene-specific increase in leukocyte alkaline phosphatase activity in rats exposed to vapors of various organic solvents

Female Wistar rats were exposed to various solvent vapors 8 h/d for 7 d. The leukocyte suspension and serum were prepared from peripheral blood and utilized for the determination of alkaline phosphatase (AP) activity with disodium phenyl phosphate as a substrate [leukocyte AP (LAP) and serum AP (SAP) assay]. While the exposure to benzene at 20 or 50 ppm did not cause significant changes in LAP activity, the exposure at 100 and 300 ppm resulted in a dose-dependent increase of LAP activity up to more than 100% over the control. No further increase was observed at 1000 or 3000 ppm. Similar exposure at 300 ppm to either toluene, m-xylene, n-hexane, trichloroethylene, methyl ethyl ketone, ethyl acetate, or methyl alcohol did not induce any changes in LAP activity. Thus, the increase in LAP activity was considered to be specific to benzene exposure. When the animals were exposed to toluene (300 ppm) in combination with benzene (300 ppm), not only was the benzene-induced leukopenia alleviated as previously reported, but the benzene-induced increase in LAP activity was no longer observed. The parallel inhibitory effects of toluene on benzene-induced increase in LAP and leukopenia suggest that a relation may exist between increase in LAP activity and leukopenia. No changes in SAP activities were observed in the rats under the exposure conditions examined.

Calculation of retention indices by molecular topology: chlorinated alkanes

This study was undertaken to test the ability of the molecular connectivity model to predict retention indices using both statistical correlation coefficients and correctly predicted elution sequences as criteria of fit. The test was performed on three groups of chloroalkanes. Regression analyses show that the molecular connectivity model successfully predicts the retention indices of chlorinated alkanes on polar and non-polar stationary phases. However, first-order molecular connectivity indices alone are not sufficient, higher order indices are demonstrated to be necessary. The results also indicate that different structural features determine the retention index values of mono- and dichlorides. For monochlorides the major factor is the size of the alkyl chain, while for dichlorides the major factor is the topological relation between the two chlorine atoms. The comparison of the results obtained with the molecular connectivity model and the empirical additive scheme reveals several important advantages of the molecular connectivity approach.

Comparative study of lipophilicity versus topological molecular descriptors in biological correlations

This paper analyzes the relative efficacies of lipophilicity vis-à-vis topological indices in the correlation of the biological properties of four groups of bioactive molecules: alcohols, barbiturates, triazinones , and ketobemidones . Wiener number (W), information-theoretic topological parameters (IC, SIC, CIC, IWD , and IWD ), and molecular connectivity indices (1 chi, 1 chi V) were used as the molecular descriptors. Results show that theoretical indices are comparable or superior to log P in biological correlations.

Comparative study of topological and linear free energy-related parameters for the prediction of GC retention indices

The different molecular connectivity indices were considered as to their capacity for describing GC retention indices of a data set consisting of molecules of different chemical families. 1 kappa describes best the chromatographic behavior on nonpolar stationary phases, whereas 3 kappa p in combination with an electronic parameter (sigma) yields the best results when using the polar stationary phases.

Physicochemical and topological correlates of the enzymatic acetyltransfer reaction

The relative potencies of a series of substituted anilines as acetyl acceptors in the enzymatic N-acetylation reaction have been correlated using physiochemical substituent constants (pi, sigma-), molecular connectivity indices (1 chi, 1 chi v), and newly formulated information-theoretic topological indices (IC, SIC). Results indicate a predominant role of the topological steric parameters in determining the rates of the N-acetyltransferase reaction.

A comparison of log P and molecular connectivity in the structure-activity analysis of some antimicrobial agents

Several congeneric series of antimicrobial agents previously studied by Hansch analysis have been investigated using molecular connectivity as the descriptor of molecular structure. In all cases connectivity gave comparable or improved correlations compared with log P, particularly where the pattern of molecular substitution was more complex. It was concluded that the use of computer-generated connectivity terms had advantages over calculated log P values in its ease of application and should be considered at least for initial screening of structure-activity data.

Derivation and significance of valence molecular connectivity

The physical basis for valence molecular connectivity was studied. The delta v and delta values are cardinal numbers describing the electronic structure of atoms in their valence states. The value delta v + delta describes the volume of a bonding atom while the value delta v - delta describes the electronegativity. By using the principle of electronegativity equalization, bond electronegativity is defined as (delta vi delta vj)-1/2, and the valence molecular connectivity index (l chi v) is derived as a sum of these bond descriptions. The valence chi index is interpreted in terms of the information encoded, describing both the volume and electronic characteristics of bonds in molecules. Examples of close relationships with molecular volume and electronic properties are shown. A new way of estimating valence state electronegativity is proposed from a count of exterjacent electrons divided by the quantum number squared for at least the first three quantum levels.

Molecular connectivity and gas chromatographic retention parameters

The relation between gas chromatographic retention parameters and molecular connectivity has been investigated for several series of compounds including hydrocarbons, compounds containing oxygen functional groups (esters, aldehydes, ketones, alcohols and ethers) and drug molecules., With the oxygenated compounds good correlation was observed with the first order valence connectivity index, whilst for the other groups multiparameter equations were required for satisfactory correlation. The effect of column to column variation within a series was also investigated.