ISSN:1062-936X    

DOI:10.1080/10629369308028811

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The relative toxicity of selected industrial organic chemicals was secured from the literature for the static 48-hTetrahymena pyriformis50% population growth impairment and the flow-through 96-hPimephales promelas50% mortality endpoints. Chemicals were selected to represent the nonpolar narcosis (aliphatic alcohols and aliphatic ketones) and polar narcosis (anilines and phenols) mechanisms of toxic action. molar volume (MV) and 1-octanol/water partition coefficient (logKow) data were generated for each chemical. High-quality, logKowdependent quantitative structure-activity relationships were observed for each chemical class and mechanism of action for both endpoints. The volume fraction (Vt) for each chemical in the target phase was determined from the toxicant concentration in the water (toxicity data), the MV, and the target/water partition coefficient (Ktw) withKtwconsidered equal toKow(1-a). Analyses of target sites, by way of “a” revealed that “a” was constant for a mechanism of action regardless of chemical class, but distinct for a given test system. MeanVtwas constant for each mechanism of action regardless of chemical class or test system. These results suggest, at least for reversible physical mechanisms, that volume fraction analyses are significant in determining the mechanism of toxic action of a chemical.

ISSN:1062-936X    

DOI:10.1080/10629369308028812

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Quantitative structure-biodegradability relationships (QSBRs) were established for a set of various organic compounds using autocorrelation components as molecular descriptors. The molecules were described by their size (van der Waals volume), electronegativity, hydrogen bonding donor and acceptor ability and lipophilicity (logP). In addition to the established models for alcohols, ketones, and aromatics, we have elaborated a model for both alcohols and ketones (5-day BOD = 0.06V0+ 1.067 logP- 0.356 (logP)2;n= 29,r= 0.958,s= 0.44,F= 145.6) and another for all the compounds (5-day BOD = 0.065V0+ 0.748 logP- 0.316 (logP)2;n= 43,r= 0.906,s= 0.575,F= 91.2).

ISSN:1062-936X    

DOI:10.1080/10629369308028813

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The log-log relationship between the bioconcentration tendency of organic chemicals in fish and then−octanol/water partition coefficients breaks down for very hydrophobic compounds. The use of parabolic and bilinear models allows this problem to be overcome. The QSAR equation log BCF = 0.910 logP- 1.975 log (6.8 10−7P+ 1) - 0.786 (n= 154;r= 0.950;s= 0.347;F= 463.51) was found to be a good predictor of bioconcentration in fish.

ISSN:1062-936X    

DOI:10.1080/10629369308028814

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Dose assessments based on multimedia exposure models require intermedia-transfer factors (ITFs) as input. These factors relate contaminant concentrations in an environmental medium (the source medium such as air. water, or soil for which measurements are available) to the exposure medium (personal air, tap water, and food products) with which humans have contact. In this paper, I use QSAR as applied to partition coefficients between soil and plants, air and plants, and between animal diet and lipid tissues as case studies for characterizing the precision of ITF estimations. These partition coefficients form the basis of total dose models required for realistic exposure/risk assessments. The quantitative relationship between ITFs and chemical properties are developed along with the estimation errors associated with these relationships. Many of these correlations have large estimation errors that limit their reliability as applied in risk assessment. I examine factors that contribute to these estimation errors and consider a “value of information” approach for increasing the precision of these estimation methods.

ISSN:1062-936X    

DOI:10.1080/10629369308028815

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

AQUAFAC, a new group contribution method for estimating aqueous activity coefficients, has been applied to a large set of organic compounds. The current work introduces 27 new group values for hydrocarbon, halogen, and non-hydrogen bond donating oxygen groups. Group values (q-values) have been derived from a data set of 621 compounds representing over 1700 individual solubility values. No correction factors were used in generating the current group values. AQUAFAC was found to give acceptable results when applied to some environmentally important compounds.

ISSN:1062-936X    

DOI:10.1080/10629369308028816

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Topological methods for molecule volume prediction based on local fragments centered on all carbons of aliphatic alkanes (C6-C11, C12) are proposed and evaluated. The LOGIC method dealing with local to global information construction is based on local environment (FRELB) partition of information, both structural and physical, and the use of these FRELs to correlate the molal volumesV. Different topological vectorial sets of various depths, dealing with atom and bond FRELs, are used to optimize the contributionsVDof a set of prime FRELs constituting the reference set structured in a hyperstructure linking 70 FRELB. The accuracy of determining fragment volumic contributions is traced by the decreasing number of hits resulting in the modeling of the C6-C11 populations. The training set of theVvalues is tested on the 355 alkanes of the C12 population. This extrapolation leads to excellent statistical results of the LOGIC method, which is a “parent structure free” similarity correlation although its application here is “aliphatic alkane” oriented. The set ofVDvalues is obtained through the combined use of several topological sets and the resolution of FREL intersections to control redundant structural information. In practice its application is simple and strictly additive.

ISSN:1062-936X    

DOI:10.1080/10629369308028817

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The dominant role of molecular mass in determining many physical properties of substances often masks significant variations of these same properties with molecular shape. Here attention is drawn to the important influence of molecular shape on molecular properties. The interdependences of the heats of vaporization, boiling points, molar volumes, molar refractions, critical temperatures, critical pressures and surface tensions of alkanes in general, and of the octanes in particular, are used to illustrate the different roles of molecular mass and shape in influencing bulk properties. The advantages of using a hierarchical separation of influences by means of orthogonal descriptors in structure-property studies are emphasized. The high interrelatedness of many physical properties in alkanes does not extend to isomeric variations, but rather reflects the dominant influence of mass on these properties. When the role of mass is removed, the influence of other structural factors is more readily discerned.

ISSN:1062-936X    

DOI:10.1080/10629369308028818

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

ISSN:1062-936X    

DOI:10.1080/10629369308028819

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

ISSN:1062-936X    

DOI:10.1080/10629369308028820

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor