Chemistry

1304 Submissions

[4] viXra:1304.0123 [pdf] submitted on 2013-04-22 22:24:14

Comment on "QSAR Modeling is not 'Push a Button and Find a Correlation': A Case Study of Toxicity of (Benzo-)triazoles on Algae"

Authors: Sierra Rayne
Comments: 2 Pages.

In their manuscript, Gramatica et al. [Mol. Inf. 2012, 31, 817-835] claim to conduct quantitative structure-activity relationship (QSAR) modeling on a suite of triazoles, benzotriazoles, and additional azo-aromatic compounds. However, a number of the compounds examined by these authors do not appear to be triazoles, benzotriazoles, or other azo-aromatic compounds. In some cases, the authors also appear to publish incorrect molecular structures which may affect the structural descriptors employed for QSAR development.
Category: Chemistry

[3] viXra:1304.0015 [pdf] submitted on 2013-04-03 21:56:39

Comment on "Sorption of Organic Chemicals to Soil Organic Matter: Influence of Soil Variability and pH Dependence"

Authors: Sierra Rayne
Comments: Pages.

In their article, Bronner and Goss [Environ. Sci. Technol., 2011, 45, 1307-1312] investigate the pH dependence of organic chemical sorption to soil organic matter. The authors report a log Koc value for benzoyl chloride in aqueous solution, despite this compound having a known hydrolysis half-life of only 16 seconds in water. This timeframe is far too short to allow the measurement of any equilibrium based partitioning coefficients. Consequently, one suspects that the log Koc value reported for benzoyl chloride is likely that of its hydrolysis product: benzoic acid. The authors also may have chosen two experimental conditions (pH 4.5 and 7.2) between which the ionization state of the carboxylic acids in the organic matter may have changed very little, and could instead have remained in effectively the same net ionization state between the two experimental pH endpoints. Thus, there does not appear to be sufficient evidence in this work to support the general claim therein that "protonation/deprotonation of carboxylic groups in humic matter has no significant influence on sorption ... even for polar organic molecules."
Category: Chemistry

[2] viXra:1304.0014 [pdf] submitted on 2013-04-03 22:15:51

Comment on "QSPR Study on the Bioconcentration Factors of Nonionic Organic Compounds in Fish by Characteristic Root Index and Semiempirical Molecular Descriptors"

Authors: Sierra Rayne
Comments: Pages.

In their article, Sacan et al. [J. Chem. Inf. Comput. Sci. 2004, 44, 985-992] construct a quantitative structure-property relationship model to predict the bioconcentration factors of purportedly nonionic organic compounds. A number of the compounds examined by these authors are not nonionic as claimed, but instead have associated pKa values that would render the molecules significantly, and - in some cases - effectively entirely, ionized under conditions relevant for bioconcentration in freshwater and/or marine aquatic systems.
Category: Chemistry

[1] viXra:1304.0007 [pdf] submitted on 2013-04-01 16:57:34

Comment on "Dependence of Persistence and Long-Range Transport Potential on Gas-Particle Partitioning in Multimedia Models"

Authors: Sierra Rayne
Comments: 1 Page.

In their article, Gotz et al. [Environ. Sci. Technol., 2008, 42, 3690-3696] use three different multimedia contaminant fate models to analyze the impact of implementing a two-particle-size polyparameter linear free energy relationship approach on metrics of persistence and long-range transport, and on calculated concentrations of semivolatile organic chemicals in the Arctic. One of the twelve compounds investigated is 2,4-D (2,4-dichlorophenoxyacetic acid), which is effectively entirely dissociated in aqueous systems. The authors do not appear to have considered the ionization of 2,4-D during their multimedia modeling exercises, particularly the effects of ionization on octanol-water and air-water partitioning behavior. Consequently, all modeling results presented for 2,4-D appear to be in significant error and should not be employed for risk assessment purposes.
Category: Chemistry