Eco-Relevant Properties of Selected Organosilicon Materials

Mazzoni, Stefano; Roy, Sandra; Grigoras, S.

doi:10.1007/978-3-540-68331-5_3

Cited by 17 publications

(14 citation statements)

References 25 publications

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“…For the reasons mentioned above, the available experimental data 11,12 are not considered reliable. It can be observed that the estimates by SPARC, COSMOtherm, and by Mazzoni et al, 31 who derived the values from estimated P L and S L data including three experimental data points, are relatively close to each other, whereas the trend estimated with EPI Suite deviates considerably. A similar general pattern exists for the two homologous series of linear dimethylsiloxanes with one or two terminal hydroxyl groups.…”

Section: ■ Computational Methodsmentioning

confidence: 68%

“…In the log K OW values of the five homologous series investigated, all literature data trends 13,16,28,31 but one 17 show a linear or nearly linear increase with the number of siloxane units (Figure 3 and Table S3). The trends for the homologous series of linear and cyclic dimethylsiloxanes derived by Bruggeman et al 16 and Mazzoni et al 31 are parallel, which is due to the fact that the values of Bruggeman et al 16 Experimental K OW values of D 4 , D 5 , and D 6 vary by more than three orders of magnitude.…”

Section: ■ Computational Methodsmentioning

confidence: 88%

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Comparing the Performance of Computational Estimation Methods for Physicochemical Properties of Dimethylsiloxanes and Selected Siloxanols

et al. 2013

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Siloxanes are used in high amounts in a wide range of applications. There is evidence that siloxanes may be persistent and bioaccumulative in the environment. Despite their high production volumes and their wide applications, only few empirical data on their physicochemical properties are available. For a selection of linear and cyclic siloxanes and siloxanols, we computed (subcooled) liquid vapor pressure, (subcooled) liquid water solubility, and the partition coefficients among air, water, and octanol with the property estimation methods, EPI Suite, SPARC, and COSMOtherm and compared the results to experimental data from the literature. The estimates obtained with the three methods generally show decent qualitative and limited quantitative agreement in the estimated trends of property data for the homologous series of linear and cyclic dimethylsiloxane oligomers. The number of measured property data available in the literature is small, but the data show considerable scatter, and their ranges exceed the differences among the three estimation methods in several cases. A strong impact of molecular configurations and conformations on substance properties could be demonstrated by means of COSMOtherm. In a case study we illustrate that these effects are large enough to greatly influence the environmental fate of the transformation products of octamethylcyclotetrasiloxane (D 4 ).

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Section: ■ Computational Methodsmentioning

confidence: 68%

Section: ■ Computational Methodsmentioning

confidence: 88%

Comparing the Performance of Computational Estimation Methods for Physicochemical Properties of Dimethylsiloxanes and Selected Siloxanols

et al. 2013

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“…The combination of partitioning properties corresponding to the vertical bar of the inverted L of elevated ACP10 (hydrophobic, but intermediate volatility) is unusual, but may actually exist for selected synthetic substances such as some cyclic organosilicone compounds (27) or perfluorinated organic substances (28). Such chemicals can occur either in the gas phase or sorbed to solids, but are too water insoluble to partition into water to any significant extent.…”

Section: Discussionmentioning

confidence: 99%

Assessing the Potential of Persistent Organic Chemicals for Long-Range Transport and Accumulation in Polar Regions

Wania

2003

Environ. Sci. Technol.

364

307

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A zonally averaged global distribution model is used to identify chemical partitioning properties and emission scenarios that favor enrichment in Arctic ecosystems. An immediate and a long-term Arctic Contamination Potential (ACP) are defined as the fraction of the total amount in global surface media that is in the Arctic after 1 and 10 years of steady emissions with a generic zonal distribution. Simulations for a two-dimensional "space" of hypothetical chemical property combinations indicate that the ACP of a perfectly persistent organic chemical is determined by a complex set of processes but tends to be higher for two combinations of partitioning properties: relatively volatile (log K OA < 9) and water soluble (4 > log K AW > -0.5) substances and substances which are semivolatile (log K OA 6.5-10) and relatively hydrophobic (log K AW > -3). Very volatile chemicals with log K OA < 6.5 and log K AW > -0.5 remain in the atmosphere even under Arctic temperature conditions, whereas very involatile chemical with a log K OA > 10 are efficiently and irreversibly deposited with atmospheric particles before reaching the Arctic. The two sets of partitioning characteristics with elevated ACP overlap in the range 6.5 < log K OA < 10 and -0.5 > log K AW > -3, which also corresponds to a log K OW range of 5 to 8, i.e., comprises substances with a potential for bioaccumulation. Organic contaminants known to accumulate in the Arctic, such as hexachlorobenzene and the lighter PCBs, indeed have such partitioning properties. Marine currents contribute significantly to the long-range transport of chemicals with log K AW < -2. Emissions to surface media greatly reduce the ACP, except for chemicals with octanol/water partition coefficients log K OW < 5. The ACP of chemicals with different partitioning properties is sensitive to different sets of environmental parameters, reflecting the different pathways which determine their global transport behavior. The ACP of most chemicals is sensitive to the temperature dependence of the partition coefficients, temperature, atmospheric mixing coefficients, and sea ice cover.

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“…At high acid concentrations (>25 wt %) an appreciable concentration (>0.1%) of trimethylchlorosilane exists in the HMDS/Me 3 SiCl equilibrium, and under these conditions, Me 3 SiCl may be the silylating agent . However, under the reaction conditions used here the concentration of Me 3 SiCl is very low and the actual silylating agent is probably trimethylsilanol on the basis of its solubility in water (3.5 × 10 4 mg/L at 25 °C), and the polar cosolvent acts as a phase-transfer agent by forming micelles capable of stabilizing and carrying the silylating agent to the hydrogel's surface.…”

Section: Resultsmentioning

confidence: 92%

A Convenient Synthesis of Silylated Silica Xerogels

et al. 1999

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Treated silica xerogels with controlled porosity and surface area were prepared by the in situ treatment of hydrogels with hexamethyldisiloxane or alkylchlorosilanes in the presence of isopropyl alcohol. The resulting hydrogels were hydrophobic and readily transferred to nonpolar organic solvents upon contact. The surface area and porosity of the xerogel were controlled by varying the pH, time, and temperature used to polymerize the hydrogel prior to treatment. In general, the surface area decreased with increases in aging time or temperature, whereas the total pore volume and pore size increased. Silylation of the hydrogel in the aqueous phase retains the structure of the hydrogel and permits isolation with minimum structure collapse. By using this technique, silylated xerogels with surface areas ranging from 200 to >700 m2/g and pore volumes of 1.5 to 3.8 cm3/g were obtained.

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Eco-Relevant Properties of Selected Organosilicon Materials

Cited by 17 publications

References 25 publications

Comparing the Performance of Computational Estimation Methods for Physicochemical Properties of Dimethylsiloxanes and Selected Siloxanols

Comparing the Performance of Computational Estimation Methods for Physicochemical Properties of Dimethylsiloxanes and Selected Siloxanols

Assessing the Potential of Persistent Organic Chemicals for Long-Range Transport and Accumulation in Polar Regions

A Convenient Synthesis of Silylated Silica Xerogels

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