Methane dilute aqueous solution

DillingWL. 1977. Interphase transfer processes. II. Evaporation rates of chloro methanes, ethanes, ethylenes, propanes, and propylenes from dilute aqueous solutions. Comparisons with theoretical predictions. Environ Sci Technol 11 405-409. 

Owicki JC, Scheraga HA (1977) Monte Carlo calculations in the isothermal-isobaric ensemble. 2 Dilute aqueous solutions of methane. J Am Chem Soc 99 7413-7418... 

The results of the calculations are presented in Table 2, which shows that infinitely dilute oxygen, carbon dioxide and methane molecules are preferentially hydrated in dilute aqueous solutions of sodium chloride. This means that water is in excess and sodium chloride is in deficit in the vicinity of a gas molecule in contrast with the random distribution of water and sodium chloride in their binary mixtures. The values of Awi2 and Aw32 are small because only the dilute region was considered in Table 2 (cj =0.3 corresponds to X3 = 0.0054). To carry out similar calculations in the nondilute region, experimental data regarding and are required and they are not available. 

Molecules of Water in the Vicinity of a Methane Molecule. First, one should clearly emphasize the difference between (1) the number of water molecules in the first hydration layer around a methane molecule and (2) the coordination number of a methane molecule in an infinitely dilute aqueous solution. Jorgensen et al. defined the number of water molecules in the first hydration layer around a methane molecule as the water molecules located between the spheres with radii 3.6 and 5.35 A. Hence, Jorgensen s first hydration layer contains both A and B species. However, the coordination number in a liquid is usually defined as the number of nearest touching neighbors and corresponds to A type molecules. 

Billing, W.L. Interphase Transfer Processes. II. Evaporation Rates of Chloro Methanes, Ethanes, Ethylenes, Propanes, and Propylenes from Dilute Aqueous Solutions. Comparisons with Theoretical Predictions, Environ. Sci. TechnoL, 11(4) 405-409 (1977). 

Direct calculation of the entropy has been attempted for infinitely dilute aqueous solutions of methane. For that application, the molecular nature of the species involved make the formulae more complicated and they have been simplified somewhat to reduce the dimensionality of the integrals that must be computed. As with the simple liquids, encouraging results have been obtained. 

J. C. Owicki and H. A. Scheraga,/. Am. Chem. Soc., 99, 7413 (1977). Monte Carlo Calculations in the Isothermal-Isobaric Ensemble. 2. Dilute Aqueous Solution of Methane. 

This article reviews the main results of our most recent work, and deals specifically with liquid water, the dilute aqueous solution of methane, and dilute aqueous solutions of monatomic cations and anions. The background for these studies is surveyed in Section I, followed by general considerations on the methodology and computational parameters. Sections III-V collect the individual results system by system, followed in Section VI by a general discussion and conclusions. 

A systematic approach to the determination of analytical potential functions was contributed from this Laboratory.The dynamics of ion-water interactions for small clusters has recently been described, and computer simulations have just been reported on liquid benzene,liquid nitrogen and liquid ammonia.The dilute aqueous solution of methane has been treated by Owicki and Scheraga " and Swaminathan, Harrison and Beveridge. Additional current applications to molecular liquids are in the newly published monograph by Watts and of course in the companion papers in this volume. 

The dilute aqueous solution of methane is a system of prominent interest in molecular liquids as the prototype of a non-po-lar molecular solute dissolved in liquid water, and is one of the simplest molecular systems where the hydrophobic effect is manifest. Moreover, a detailed knowledge of the structure of the methane-water solution at the molecular level can provide leading information on the interaction of water with dissolved hydrocarbon chains in general, and thereby contribute to the theoretical basis for understanding the role of water in maintaining the structural Integrity of biological macromolecules in solution. 

Early computer simulation work on the methane-water system was reported by Dashevsky and Sarkisov. Recent theoretical studies of the methane-water system are the initio molecular orbital calculations of the methane-water pairwise interaction energy by Ungemach and Schaefer and the Monte Carlo computer simulation on the dilute aqueous solution in the isotherroal-isobaric ensemble by Owickl and Scheraga. 

A recent Monte Carlo study of structure of the dilute aqueous solution of methane from this Laboratory involves one methane molecule and 124 water molecules at 25°C at liquid water density. The configurational energy of the system is developed under the assumption of pairwise additivity using potential functions representative of initio quantum mechanical calculations for both the water-water and methane-water interactions. For the water-water interaction we have carried over the MCY-CI potential function used in our previous study of the structure of liquid water reviewed in the preceeding section. For the methane water interaction energy, we have recently reported an analytical potential function representative of quantum mechanical calculations based on SCF calculations and a 6-31G basis set, with correlation effects Included via second order Moller-Plesset (MP) corrections,52 This function was used for the methane-water con-... 

An analysis of the structure of the dilute aqueous solution of methane was also developed in terms of quasicomponent distribution functions and stereographic views of significant molecular structures. The coordination number of methane in this system was calculated on the basis of 5.38, fixed at the first minimum In the methane-water radial distribution function. A plot of the mole fraction of methane molecules x (K) vs. their corresponding water coordination number is given in Figure 7. 

Figure 6. Calculated methane-water radial distribution g(Rj ui. center of mass separation R from Monte Carlo computer simulation for the dilute aqueous solution of methane at T = 25°C...

Figure 7. Calculated quasicomponent distribution function xcfKj vs. methane coordination number K for the dilute aqueous solution of methane...

Ferrocene (46.4 g., 0.250 mole) (Note 1) is added to a well-stirred solution of 43.2 g. (0.422 mole) of bis(dimethylamino)-methane (Note 2) and 43.2 g. of phosphoric acid in 400 ml. of acetic acid in a 2-1. three-necked round-bottomed flask equipped with a condenser, a nitrogen inlet, and a mechanical stirrer (Note 3). The resulting suspension is heated on a steam bath under a slow stream of nitrogen (Note 4) for 5 hours (Note 5). The reaction mixture, a dark-amber solution, is allowed to cool to room temperature and is diluted with 550 ml. of water. The unreacted ferrocene is removed by extracting the solution with three 325-ml. jiortions of ether. The aqueous solution is then looled in ice water and made alkaline by the addition of 245 g. 

The crude product is pure enough for most purposes. However, for catalytic reduction to bis(2,4,6-trimethylcydohexyl)-methane, the residual add must be removed by dissolving the solid in hot benzene and stirring or shaking with dilute aqueous sodium carbonate solution until the washings are basic this is followed by a water wash and drying. 

The study of very dilute solutions of simple solutes such as argon, methane, and the like is of interest for various reasons. First, these solutions reveal some anomalous properties in comparison with non-aqueous solutions and therefore present an attractive challenge to chemists, physicists, and biochemists. Second, aqueous solutions of a simple solute may be viewed as pure water subjected to a weak external field of force. Therefore, the study of such systems can contribute to our understanding of pure liquid water itself. Finally, and most... 

Trimethylaluminum (20 mL of a 2 M solution in toluene, 40 mmol) is added to titanocene dichloride (5.0 g, 20 mmol) under inert gas. The resulting mixture is stirred at room temperature for 3 d with evolution of methane. The mixture is then cooled to 0 °C and a solution of phenyl benzoate (4.0 g, 20 mmol) in THE (20 mL) is added over 5 min. The resulting mixture is left to warm to room temperature within 45 min and is then diluted with anhydrous diethyl ether (50 mL). Approximately 50 drops of a 1 M aqueous sodium hydroxide solution are carefully added over 10-20 min. When gas evolution has ceased anhydrous sodium sulfate is added and the slurry is filtered through a pad of Celite. After rinsing with diethyl ether the combined filtrates are concentrated and the product is purified by column chromatography (150 g basic alumina, pentane/diethyl ether 9 1). 2.8 g (70%) of the title compound is obtained. NMR (250 MHz, CDCI3) 5 4.45 (d, 2.3 Hz, IH), 5.05 (d, 2.3 Hz, IH), 7.06-7.11 (m, 3H), 7.29-7.38 (m, 5H), 7.66-7.70 (m, 2H). 

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