Heavy/deuterated water

During the 10-year period in which the data in Tables V and VI were acquired, the electronic solar neutrino experiment in the Sudbury Neutrino Observatory (SNO) in Canada was completed and began data taking. The heart of SNO is a transparent acryclic sphere holding 1000 tons of heavy (deuterated) water with which to observe the reaction initiated by Ve from the in the sun. 

Sutin et al have made a detailed study of the chloride-catalysed paths in deuterated water media, the exchange occurring more slowly in this solvent than in water. Accurate values of, in both water and heavy water, were obtained by spectrophotometry and enabled more precise rate parameters to be calculated. For aqueous media, values are 22.8 l.mole sec fork (n = 0.50 Af and 20 °C),... 

The enhancement of the fluorescent yield of terbium, europium, and gadolinium in heavy-water solutions was studied by Kropp and Windsor (105). They observed substantial increases in emission intensities for both terbium and europium compounds when ordinary water was replaced by deuterated water. No appreciable increase was observed for gadolinium, however. For terbium they also obtained the fluorescent lifetimes of the 5D4 state. 

The concentrations of the different intermediates are determined by the equilibrium constants. The observation of immonium ions [Eq. (5)] in strongly acidic solutions by ultraviolet and NMR spectroscopy also Indicates that these equilibria really exist (23,26). The equilibria in aqueous solutions are of synthetic interest and explain the convenient method for the preparation of 2-deuterated ketones and aldehydes by hydrolysis of enamines in heavy water (27). 

In 1933, Schoenheimer, who was medically qualified and had been working with Aschoff in the Pathology Institute in Freiburg, moved to Columbia University, New York, and was joined the next year by David Rittenberg. Rittenberg had just spent some time in Urey s laboratory in the Rockefeller Institute learning techniques for handling deuterium. Their first experiments concerned the metabolism of deuterated fatty acids in rats and the demonstration (see below) that 2H from heavy water was incorporated by the animals into fatty acids and cholesterol. 

Organolithium reagents, like Grigncird reagents, are bases that react with proton (or deuteron) donors. Figure 14-13 illustrates this reaction. In this reaction D2O (heavy water) is the deuterated form of water in which the hydrogen atoms (H) are replaced with deuterium atoms (D). 

Within the IR spectroscopy arena, the most frequently used techniques are transmission-absorption, diffuse reflectance, ATR, specular reflectance, and photoacoustic spectroscopy. A typical in situ IR system is shown in Fig. 7. Choosing appropriate probe molecules is important because it will influence the obtained characteristics of the probed solid and the observed structure-activity relationship. Thus, the probe molecules cover a range from the very common to the very rare, in order to elucidate the effect of different surfaces to very specific compounds e.g. heavy water and deuter-ated acetonitrile, CDsCN). The design of the IR cell is extremely important and chosen to suit the purposes of each particular study. For catalytic reactions, the exposure of catalytic metals must be eliminated in cell construction, otherwise the observed effect of the catalyst may not be accurate. 

The H NMR spectra of organic compounds are usually obtained in an aprotic solvent at concentration levels of a few percent. The most widely used solvent is deuterated chloroform (CDC13), sufficiently polar to dissolve most organic compounds. Acetone-r/6 (C3D60), methanol-e 4 (CD3OD), pyridinc-r/5 (C5D5N) and heavy water (D20) are also used. 

Deuterated gel. Dried curdlan powder was mixed into a 2% w/v suspension in heavy water. This suspension was spread on a glass plate and placed in an airtight container, shown schematically in Figure 5. The container was heated to approximately 100°C, thus gelling the polymer. The film was washed in D2O, to stop the rapid loss of D2O from the hot film, and then carefully removed and dried. (All operations except that of heating were carried out in the dry-box.)... 

Deuterated C60 C60D36 was synthesized in n-hexane using the same procedure detailed above for C60H36 using Zn dust and 37% deuterium chloride (DC1) in heavy water (D20). After complete reduction also the electronic absorption spectrum of C60D36 is dominated by a maximum at 217 nm and the molar extinction coefficient was determined e217 = 16480 L cm-1 mol-1. 

For all samples pretreated under vacuum at temperatures in the 298 - 573 K range, optimal H/D exchange was observed if D20 adsorption was performed for lh at room temperature, followed by evacuation at the same temperature as pretreatment. Deuteration may be considered as a rehydration of the surface, with heavy water, followed by H/D exchange. Product HDO and H20 molecules are thermally desorbed in the evacuation step. In this way, H/D exchange occurs without rehydroxylation, the deuterated silica has a deuterated surface silanol distribution identical to the initial pretreated silica. 

Deuteration of silica gel therefore shows to be governed by the rehydration capacity of the substrate. At low pretreatment temperature the extent of H/D exchange is limited by internal silanols, which may not be reached by (heavy) water molecules. At high pretreatment temperature the exchange is restricted by the low physisorption ability of the isolated silanols. 

Next, a correlation among Sa, Xam(X), the fraction of the accessible part (by heavy water) at equilibrium, as determined by the deuteration IR method, Xac(IR)> ar)d the relative amount of the higher field peaks of the C4 carbon peaks, Xh(NMR), were examined for samples having cellulose crystal form II, so as to clarify the factors contributing to Sa. In this case, Xi,(NMR) was estimated from Eq. (60) ... 

Furan has also been labeled with heavy water on supported catalysts (chromium, zinc, and manganese oxides promoted with K2C03) at a temperature of 350°.117 Deuterated furan has also been obtained from the vapor phase decarbonylation of furfural over mixed oxide catalysts in the presence of heavy water. Both of these systems utilize extreme experimental conditions and the methods outlined in Table XII are to be preferred for preparative labeling. 

This mechanism was tested by use of C-labeled carbon dioxide (Barker, 1943 Buswell and Sollo, 1948 Stadtman and Barker, 1949, 1951 Pine and Barker, 1956 Baresi et al, 1978). Essentially none of the methane was found to be derived from carbon dioxide. Methane is derived entirely from the methyl carbon atoms and carbon dioxide is derived exclusively from carboxyl carbon atoms. Van Neil s mechanism is clearly not valid because the methyl carbon atom is not oxidized to carbon dioxide. Other work has been done to ascertain whether hydrogen atoms are removed during the fermentation of acetic acid, and whether the methyl group is incorporated intact into methane (Pine and Barker, 1954). Water and heavy water were used with deuterated and nondeuterated acetic acid. Acetic acid labeled in the methyl group, when used as the substrate, showed that the isotopic content of acetic acid and methane are the same. Unlabeled acetic acid fermented in the presence of heavy water indicated that about one atom of deuterium per molecule of methane formed is derived from heavy water. It was concluded that the methyl group is transferred from acetic acid to methane as a unit without the loss of attached hydrogen or deuterium atoms. 

Weigl studied the exchange reaction between ascorbic acid and heavy water. An examination of the 0—H and C—H stretching frequency region of the normal and the deuterated compound led him to the conclusion that ascorbic acid contains labile hydrogen atoms attached to both carbon and oxygen. 

Two articles appear in 1975 which cover most of the literature on the use of stable isotopes up to that year. The first was a review of studies with deuterated drugs and it also covered the toxicological and therapeutic aspects of deuterium oxide (heavy water). The second article reviewed mass spectrometry. Since the mass spectrometer has been the instrumental tool for most of the research that employs stable Isotopes, the article covered many references on stable isotopes as well. 

The most widely used solvent is deuterated chloroform (CDCI3) which is sufficiently polar to dissolve the majority of organic compounds. Also used are acetone-d5(C3DgO), methanol-d4(CD30D, pyridine-d5(C5D5N) or heavy water (D2O). 

The theoretical description in terms of spherical harmonics also yields a relation between the size polydispersity index p of the microemulsion droplets and the bending elastic constants [43]. The quantity p is accessible by SANS [51, 52, 59-61]. For polydisperse shells as obtained by using deuterated oil and heavy water for the preparation of the microemulsion (contrast variation), one can account for the droplet polydispersity by applying an appropriate form factor, e.g. containing a Gaussian function to model the size distribution [52, 59, 62]. A possible often-used choice is the following form factor... 

By contrast, intentional fractionation to yield heavy water (thousands of tonnes annually) or deuterated chemicals implies an atomic weight approaching 2.014, and great care should be taken to avoid contamination of normal samples when working with or disposing of such enriched materials. 

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