Water, coordination number

These studies showed that sulfonate groups surrounding the hydronium ion at low X sterically hinder the hydration of fhe hydronium ion. The interfacial structure of sulfonafe pendanfs in fhe membrane was studied by analyzing structural and dynamical parameters such as density of the hydrated polymer radial distribution functions of wafer, ionomers, and protons water coordination numbers of side chains and diffusion coefficients of water and protons. The diffusion coefficienf of wafer agreed well with experimental data for hydronium ions, fhe diffusion coefficienf was found to be 6-10 times smaller than the value for bulk wafer. 

If the dissolved gas is ethane with a water coordination number of 24, the transformation of empty cavities (with a coordination number of 20) is likely to be rapid, due to the high ratio (3 1) of 51262 to 512 cavities in si. If the dissolved gas is propane with a coordination number of 28, transformation to sll is likely to be slow because 51264 cavities are outnumbered by 512 cavities by a factor of two. 

Central America and Caribbean 316, 520-3 Europe and Turkey 505-9 South America 316, 522 -3 USA 316, 513-19 see also under drinking water coordination number 10, 12 copper arsenate 281 copper mines/smelting 115, 164,404 history of 278... 

Cu isotopes both with nuclear spin I-3/2. The nucle r g-factors of these two isotopes are sufficiently close that no resolution of the two isotopes is typically seen in zeolite matrices. No Jahn-Teller effects have been observed for Cu2+ in zeolites. The spin-lattice relaxation time of cupric ion is sufficiently long that it can be easily observed by GSR at room temperature and below. Thus cupric ion exchanged zeolites have been extensively studied (5,17-26) by ESR, but ESR alone has not typically given unambiguous information about the water coordination of cupric ion or the specific location of cupric ion in the zeolite lattice. This situation can be substantially improved by using electron spin echo modulation spectrometry. The modulation analysis is carried out as described in the previous sections. The number of coordinated deuterated water molecules is determined from deuterium modulation in three pulse electron spin echo spectra. The location in the zeolite lattice is determined partly from aluminum modulation and more quantitatively from cesium modulation. The symmetry of the various copper species is determined from the water coordination number and the characteristics of the ESR spectra. 

A chiral lanthanide complex catalyzes asymmetric Mukaiyama aldol reactions in aqueous media (Scheme 24). The changes in the water-coordination number is key to the mechanism of die catalytic reaction. The precatalysts yielded -hydroxy carbonyl compounds from aliphatic and aryl substrates widi high diastereomeric ratios and enantiomeric excesses of up to 49 1 and 97%, respectively. 

In contrast, when large Cs+ ions are in the solution, water molecules are loosely caged around these ions. For the water molecules comprising the cages, one position has been taken by these large ions, and so only three other water molecules can be hydrogen-bonded to them and counted as primary waters of coordination thus the water-water coordination number of these cation-bonded water molecules is less than that of a pure water cluster. As more ions are in the solution, more water molecules will be around ions, and consequently, for large alkali cations the water-water hydration number decreases monotonically with an increase in salt concentration. 

FIGURE 4.1 The first shell water-water coordination numbers in different salt solutions for various solution concentrations. (From Du, H., Rasaiah, J. C., and Miller, J. D., J. Phys. Chem. B, 111 209, 2007. With permission.)... 

Gd(III) complexes in aqueous solution an understanding of the parameters that define the erystal field interactions (cfi) among different contrast agents the hydration number, i.e., the water coordination number in aqueous and biological matrices the gadolinium-water proton distance. The first area was reviewed recently by Borel and eoworkers [17] in this series, and will only be treated briefly here. The other three areas are covered in more detail. 

Scheme 8.2 Evaluation of the Water Coordination Number of Lanthanide Triflate-Based Catalysts Using Dynamic Luminescence Decay Measurements. With permission from Ref [57],...

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. 

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