Deuterium composition

RATIO OF FRACTION OF DEUTERIUM (Px ) IN EACH STRUCTURAL POSITION OF A SOLUBLE PRODUCT TO THE DEUTERIUM COMPOSITION (F ) IN THE SOLUBLE PRODUCT... 

R(t) is the relevant function to be analyzed for extraction of the kinetics. However, in micellar systems where the micelles are not fully proteated/deuterated or there is residual contrast between core and shell, ncaiUnear interference scattering contributions are present. In order to take this into account, a more accurate description of the time-dependent scattering intensity is necessary. A scattering model, where the time-dependent hyrogen/deuterium composition of the core and shell of the micelles is built into a kinetic core-shell model, is described next. 

Hydrogen and deuterium composition profile Vibrational spectra of polymer surface adjacent to ATR-crystal surface Vibrational spectra of thin films and absorbed layers... 

In practice, other elemental compositions could add up to 17. For example, OH (oxygen = 16, hydrogen = 1), CDHj (carbon = 12, deuterium = 2). 

The recognition in 1940 that deuterium as heavy water [7789-20-0] has nuclear properties that make it a highly desirable moderator and coolant for nuclear reactors (qv) (8,9) fueled by uranium (qv) of natural isotopic composition stimulated the development of industrial processes for the manufacture of heavy water. Between 1940 and 1945 four heavy water production plants were operated by the United States Government, one in Canada at Trail,... 

Properties of Light and Heavy Hydrogen. Vapor pressures from the triple point to the critical point for hydrogen, deuterium, tritium, and the various diatomic combinations are Hsted in Table 1 (15). Data are presented for the equiUbrium and normal states. The equiUbrium state for these substances is the low temperature ortho—para composition existing at 20.39 K, the normal boiling point of normal hydrogen. The normal state is the high (above 200 K) temperature ortho—para composition, which remains essentially constant. 

A natural substance of elemental composition Cis/Z/ Og was isolated from the plant Centaurea chilensis (Compositae). What is the structure and relative configuration of the substance given its H NMR spectrum 10 with (top) and without (bottom) deuterium exchange 10 ... 

Indicate mechanisms that would account for the formation of each product. Show how the isotopic substitution could cause a change in product composition. Does your mechanism predict that the isotopic substitution would give rise to a primary or secondary deuterium kinetic isotope effect Calculate the magnitude of the kinetic isotope effect from the data given. 

Even though a sample may show a satisfactory average deuterium content per mole as reported in the earlier literature, its true isotope composition can be quite unsatisfactory when analyzed by mass spectroscopy. The saturated product from the deuteration of 1-hexene, for example, shows an average deuterium content of almost 2.0 however, it consists of virtually all species from do to di4 with the species do to dg predominating. ... 

The rhodium catalyst (46 mg) is dissolved in acetone (10 ml) in a microhydrogenation apparatus which is then flushed three times with deuterium gas. After stirring the solution in an atmosphere of deuterium for about 1 hr the deuterium uptake ceases and constant pressure is attained. 5a-Cholest-2-ene (136, 19.5 mg) is added and the stirring continued until deuterium uptake ceases (about 3/4 hr). The solvent is evaporated to dryness and the residue is extracted with hexane and the resulting solution filtered through a small alumina column (3 g, activity 111). Evaporation of the hexane gives 2, 3 -d2-5oc-cholestane (137) 18 mg, 92% mp 78-79° isotope composition 94%d2,5%d, andl%do. ... 

Replacement of halides with deuterium gas in the presence of a surface catalyst is a less useful reaction, due mainly to the poor isotopic purity of the products. This reaction has been used, however, for the insertion of a deuterium atom at C-7 in various esters of 3j -hydroxy-A -steroids, since it gives less side products resulting from double bond migration. Thus, treatment of the 7a- or 7j5-bromo derivatives (206) with deuterium gas in the presence of 5% palladium-on-calcium carbonate, or Raney nickel catalyst, followed by alkaline hydrolysis, gives the corresponding 3j3-hydroxy-7( -di derivatives (207), the isotope content of which varies from 0.64 to 1.18 atoms of deuterium per mole. The isotope composition and the stereochemistry of the deuterium have not been rigorously established. 

Data refer to H2 of normal isotopic composition (i.e. containing 0.0156 atom % of deuterium, predominantly as HD). All data refer to the mixture of ortho- and puru-forms that are in equilibrium at room temperature. 

It is claimed that the limiting value of k bs, 2.81 x 10" sec-1, represents the rate coefficient for the rearrangement reaction above (k,). The ring deuterium isotope effect kH kD was re-determined for this individual rate coefficient for rearrangement by finding the limiting value in the presence of added N-methylaniline and was found to be 2.4 at two different acidities, as compared with 1.7 for the ratio of the observed composite rate coefficients, as expected, since no isotope effect would be predicted for the de-nitrosation step. 

The composition of the Earth was determined both by the chemical composition of the solar nebula, from which the sun and planets formed, and by the nature of the physical processes that concentrated materials to form planets. The bulk elemental and isotopic composition of the nebula is believed, or usually assumed to be identical to that of the sun. The few exceptions to this include elements and isotopes such as lithium and deuterium that are destroyed in the bulk of the sun s interior by nuclear reactions. The composition of the sun as determined by optical spectroscopy is similar to the majority of stars in our galaxy, and accordingly the relative abundances of the elements in the sun are referred to as "cosmic abundances." Although the cosmic abundance pattern is commonly seen in other stars there are dramatic exceptions, such as stars composed of iron or solid nuclear matter, as in the case with neutron stars. The... 

In the spent solvents from E10, Table II, naphthalene and tet-ralin were the major products, and the four others were minor products which totaled 8 mole %. In El9, Table III shows that 20 mole % of the four minor products were formed, indicating that an appreciable fraction of tetralin was converted to species less effective in the donor process. Protium from the coal, deuterium from the gas phase or deuterium from the Tetralin is needed to form these products. An examination of the isotopic composition of each of the four products as shown in the bottom halves of Tables II and III allows observations to be made about their formation. 

The coal residue was separated into a THF-soluble fraction and a THF-insoluble residue. The wt % yields and atom % 2H compositions are given in Table I. The coal residue was 6 wt % soluble in tetrahydrofuran. The soluble fraction had 23 atom % 2H content. Evaluation of the 2H NMR data showed that 85 wt % of this fraction was derived from the coal and that its deuterium content was 10%. The chemically-bonded naphthalene-d8 content of the THF-soluble fraction, estimated from the 2H NMR data, was about 15 wt % or approximately 1 wt % of the coal. The insoluble residue had 6 atom % 2H content. This indicates that the residue contained approximately 1 wt % chemically-bonded naphthalene which was estimated from the difference in the atom % 2H content of the insoluble residue and recovered naphthalene-d8. This gives a total chemically-bonded naphthalene-d8 content of approximately 2 wt %. Similar results were obtained in extraction experiments made with phenanthrene (30), where it was found that 3-7 wt % of the phenanthrene was chemically linked to the coal product. 

An investigation of the isotopic composition of the Decal ins, which were formed as minor products in the donor solvent experiments, showed that cis-Decalin was formed preferentially. Its formation and its increased protiurn incorporation may have resulted from increased contact with the coal surface. Trans-Decal in contained less protiurn than the Tetralin, which suggests that most of the trans-Decalin was formed with deuterium from the Tetralin-di2 and deuterium gas. 

The special position of the Earth among the terrestrial planets is also shown by the availability of free water. On Venus and Mars, it has not until now been possible to detect any free water there is, however, geological and atmospheric evidence that both planets were either partially or completely covered with water during their formation phase. This can be deduced from certain characteristics of their surfaces and from the composition of their atmospheres. The ratio of deuterium to hydrogen (D/H) is particularly important here both Mars and Venus have a higher D/H ratio than that of the Earth. For Mars, the enrichment factor is around 5, and in the case of Venus, 100 (deBergh, 1993). 

Both vanadium and niobium metals form dihydrides only at high pressures(27), and numerous phases with hydrogen compositions less than one(28). Experiments were performed to saturate vanadium clusters with deuterium. Figure 4 is a plot of the number of deuteri urn molecules found in the products. The solid straight lines are for D V ratios of 1 and 2. The corresponding curved dashed lines include corrections for some bulk atoms(2c). The best fit to the data including only surface atoms indicate a stoichiometry of 1.5. It is likely that this high surface stoichiometry is an indication of bulk i ncorporation of deuterium. 

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