Water compared with deuterium oxide

To dearly distinguish between these two modes of solvent penetration of the gel, we immersed poly(acrylamide-co-sodium methacrylate) gels swollen with water and equilibrated with either pH 4.0 HQ or pH 9.2 NaOH solution into limited volumes of solutions of 10 wt % deuterium oxide (DzO) in water at the same pHs. By measuring the decline in density of the solution with time using a densitometer, we extracted the diffusion coefficient of D20 into the gel using a least squares curve fit of the exact solution for this diffusion problem to the data [121,149]. The curve fit in each case was excellent, and the diffusion coefficients obtained were 2.3 x 10 5cm2/s into the ionized pH 9.2 gel and 2.4 x 10 5 cm2/s into the nonionized pH 4.0 gel. These compare favorably with the self diffusion coefficient of D20, which is 2.6 x 10 5 cm2/s, since the presence of the polymer can be expected to reduce the diffusion coefficient about 10% in these cases [150], In short, these experiments show that individual solvent molecules can rapidly redistribute between the solution and the gel by a Fickian diffusion process with diffusion coefficients slightly less than in the free solution. 

Table 21.1 compares some of the common properties of H2O with those of D2O. Deuterium oxide, or heavy water as it is commonly called, is used in some nuclear reactors as a coolant and a moderator of nuclear reactions (see Chapter 23). D2O can be... 

A mechanism which is consistent with the various experimental results for olefin formation involves the initial abstraction of the hydrazone proton (103 - 106)82 In this case, however, expulsion of the tosylate anion is associated with the abstraction of a second hydrogen from C-16 instead of hydride attack on the C=N bond (compare 97 - 98 and 106 - 107). Expulsion of nitrogen from the resulting intermediate (107) yields an anion (108) which is most probably stabilized in the form of a metal complex and can be readily decomposed by water to give an olefin (109). This implies that 17-d1-androst-16-ene (104) can be prepared by using deuterium oxide as the sole deuterated reagent.82... 

An increase in solvent polarity further favours the open-chain tautomer in water there is no evidence for any cyclic form [79], This is remarkable in view of the fact that the furanose/pyranose equilibria of sugars, which are interconverted through the open-chain form, are also solvent-dependent [80, 81, 159], Arabinose, for example, in [Dsjpyridine consists of 66 cmol/mol pyranose form (a y9 = 33 33) and 34 cmol/mol furanose form (a y9 = 21 13), compared with 95.5 cmol/mol pyranose form (a y9 = 60 35.5) and 4.5 cmol/mol furanose form (a y9 = 2.5 2.0) in deuterium oxide as solvent [80, 159],... 

Solvent Effects. Kinetic parameters for the reaction of [Pt(dien)Br]+ with 3-cyanopyridine have been determined in deuterium oxide solution, in order to make a comparison of reactivities in deuterium oxide and in ordinary water. To avoid any complications from protium-deuterium exchange between solvent and co-ordinated ligand, the perdeuterio-diethylenetriamine complex was used as substrate in deuterium oxide solvent. The kinetic parameters are compared in Table 1. The results were discussed in terms of an associative mechanism and the smaller solvating effects of D2O compared with HgO. ... 

The infrared spectra were recorded on a Perkin-Elmer model 237 grating spectrometer. Alkali halide and silver chloride cell windows were used with appropriate Teflon spacers to obtain comparable band intensities from several concentrations of PEO in benzene and deuterium oxide. A variable path cell was used in the reference beam to compensate for solvent absorption in the spectra of benzene solutions with low concentrations of PEO. Deuterium oxide was used instead of water as a solvent because, in the spectral regions of interest, it contributed less back-ground absorption. All solution compositions are given in volume per cent. 

Let us now turn to a comparison of theory with experiment. Comparing (95), (84), and (68), we find that the dependence of the photocatalytic effect K on the position of the Fermi level at the surface s and in the bulk cv of an unexcited sample for the oxidation of water is the same as for the oxidation of CO or for the hydrogen-deuterium exchange reaction. For this reason, such factors as the introduction of impurities into a specimen, the adsorption of gases on the surface of the specimen, and the preliminary treatment of the specimen will exert the same influence on the photocatalytic effect in all the three reactions indicated above. The dependence of K on the intensity I of the exciting light must also be the same in all the three cases. 

The interaction of deuterium water vapor with cerium has been studied in XPS recently by Koel et al. (1980). A very similar behavior as compared to the heavy rare earths was found, in that a nonlinear uptake was obtained after exposures of about SOL. Calculations of overlayer thickness using the Ce 3d metal peaks indicated, however, that the ratio corresponds to more than one monolayer of OD. Another argument for the formation of a bulk hydroxide or oxy-hydroxide was derived from the different splitting of the peaks associated with each component of the 3d spin-orbit doublet in the metal. This splitting was 3.7 eV upon oxidation by O2 and 4eV upon exposure to water, indicating a different chemical species. 

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