Hydrophobic Solvation: Aqueous Methane Solutions

The underlying molecular mechanisms of macroscopic excess properties were studied by molecular dynamics simulations for different compositions of methanol-water mixtures. Structural data (nearest neighbor relationships, clustering analysis) and dynamic data (hydrogen bond lifetimes, rotational autocorrelation, translational diffusion) were evaluated. Nearest neighbor relationships provide quantitative evidence and a pictorial description of incomplete mixing at the molecular level as a source for mixture anomalies, while a comparative study of water surrounding methyl moieties versus water in the bulk-like environment provides evidence against the hydrophobicity model of clathrate-like hydration. Furthermore, the formation or breakdown of the system-wide hydrogen bonding network at a critical threshold of approximately equimolar mixture is perceived to separate the mixture system into two hydrogen bonding regimes: hydrogen-bonded water clusters embedded in methanol for mixtures with low water content and methanol molecules within a system-wide hydrogen-bonded water network for mixtures with high water content.

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Determination of the Solubility Limit of Tris(dibenzylideneacetone) dipalladium(0) in Tetrahydrofuran/Water Mixtures

Franzen

2011

J. Chem. Educ.

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Determination of the solubility limit of a strongly colored organometallic reagent in a mixed-solvent system provides an example of quantitative solubility measurement appropriate to understand polymer, nanoparticle, and other macromolecular aggregation processes. The specific example chosen involves a solution of tris(dibenzylideneacetone) dipalladium(0), Pd2(dba)3, in THF/H2O mixtures, which has the desired properties of high absorption in the visible range (λmax = 528 nm) and significant difference in solubility in the two solvents THF and H2O. Pd2(dba)3 is readily available, safe, and commonly used in nanoparticle syntheses. The application of Flory−Huggins theory permits the fit of a quantitative model to data obtained from a straightforward laboratory experiment that can be conducted in less than 3 h. The absorbance of this compound is easily measured by UV−vis absorption spectroscopy. The application of the Beer−Lambert law to the data in this experiment is a useful exercise for students because the absorbances span three orders of magnitude.

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Hydrophobic Solvation: Aqueous Methane Solutions

Cited by 6 publications

References 20 publications

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Incomplete mixing versus clathrate-like structures: A molecular view on hydrophobicity in methanol–water mixtures

Determination of the Solubility Limit of Tris(dibenzylideneacetone) dipalladium(0) in Tetrahydrofuran/Water Mixtures

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