Deuterium chemical separation

As we noted that in most hydrogen-consuming or -producing reactions there is a separation of the isotopes. We became intrigued with the possibility of finding a chemical separation method which would not consume enormous quantities of electricity and could make deuterium and heavy water inexpensive. 

As the most electroactive gas, H2 was the first object of electrochemical separation. In an unusual circumstance, separation was not proposed from a mixture of chemically dissimilar species such as N2, C02, etc., but rather, from deuterium, D2. It had been noted as early as the late 1930 s [4] that H2 is preferentially evolved on several cathode materials over HD or D2 during electrolysis of water ... 

The best insight into the relaxation behavior of star polymers in dilute solution can be expected if, in addition to the whole star system, different parts of the star are considered separately. This can be achieved easily by neutron scattering techniques on systems where not only the entity of arms, but also single arms, the core or shell parts are labelled by proton deuterium exchange. With respect to the core-shell labelling it is convenient to build up the arms as diblock copolymers of A-B type with protonated or deuterated but otherwise chemically identical A and B blocks. 

The naphthalene extraction experiment was carried out under similar conditions except that nitrogen was used as cover gas instead of deuterium. The spent naphthalene-d8 was separated from the residue by distillation at reduced pressure. The residue was solvent fractionated with tetrahydrofuran (J. T. Baker Chemical Co.). 

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. 

Isotopes of hydrogen. Three isotopes of hydrogen are known H, 2H (deuterium or D), 3H (tritium or T). Isotope effects are greater for hydrogen than for any other elements (and this may by a justification for the different names), but practically the chemical properties of H, D and T are nearly identical except in matters such as rates and equilibrium constants of reactions (see Tables 5.1a and 5.1b). Molecular H2 and D2 have two forms, ortho and para forms in which the nuclear spins are aligned or opposed, respectively. This results in very slight differences in bulk physical properties the two forms can be separated by gas chromatography. 

Harold Clayton Urey, 1893-. Professor of chemistry at the Institute for Nuclear Studies at the University of Chicago and at the University of California. In 1931 Dr. Urey and his collaborators discovered deuterium, the heavy isotope of hydrogen. Pie has carried out notable researches on the entropy of gases and on the properties and separation of isotopes and has studied the chemical evidence of the earth s origin. 

Similar results have been obtained for methane 12) and for ethane 19). The values quoted in Table II also illustrate the point that the distribution of deuterium between hydrogen and propane differs from the value expected for a random distribution. With the ratio of pressures used, the expected percentage for the mean deuterium content of the hydrocarbon would be 33.3, which is substantially less than the experimental value of 40.9 %. This type of deviation is also found with other hydrocarbons, but it does not affect the validity of using classical theory for the calculation of the interconversion equilibrium constants in studies of mechanism of exchange reactions. More accurate values for these equilibrium constants are necessary, however, if one is interested in the separation of isotopes by chemical processes. 

The difference in reactivity was also found for the paramagnetic surface defects -(=Si-0-)3Si radicals [16]. Since the observed effects are due to the difference in the structure of the nearest environment of the surface silicon atom, it is most pronounced when this atom acts as an active site. This difference should cease with an increase in the number of chemical bonds that separate the active site and surface silicon atom of the solid with which it is linked. They are almost absent for the (=Si-0-)3Si-CFl2- CF[2 radical in which the active site is localized on the terminal carbon atom [16]. For this reason, it is desirable to have a probe in the immediate contact with a lattice silicon atom. The Si-H group fits best these requirements. Such groups can be obtained upon the interaction of the silyl-type radicals with the hydrogen or deuterium molecules (cf. Section 6.3). The IR band due to the stretching vibrations of the Si-Fl bonds obtained upon the hydrogenation of silyl radicals ... 

The proton signals of uridine (36) dissolved in deuterium oxide are well separated at 220 MHz, and a complete analysis and simulation of the spectrum by means of the LAOCOON II computer program (see Section V, p. 74) has been reported.107 It was concluded from the temperature-independence of the coupling constants and chemical shifts of the D-ribofuranoid moieties of uridine, /3-pseudouridine (40), and a-pseudouridine (41), that each of these compounds... 

It is only in the case of hydrogen H (weight i) and deuterium D (weight 2), discovered by Urey (1933), that the relative difference is so large that a small but observable difference in all physical and even in chemical properties occurs. Thus the separation of pure D2 is possible by repeated electrolysis of water, in which the separated hydrogen gas is less rich in the heavy isotope than corresponds to the ratio in the water 1 4000. The deuterium therefore accumulates in the residual liquid of technical installations for the electrolytic production of hydrogen (Norway). 

The analysis of a technical poly(ethylene oxide) with respect to chemical composition and degree of polymerization has been performed by Pasch and Hiller [210]. This investigation was conducted under conditions which are common for HPLC separations, i.e. sufficiently high flow rate, moderate sample com-centration, and on-flow detection. Using an octadecyl-modified silica gel as the stationary phase and an eluent of acetonitrile/deuterium oxide 50 50 (v/v), the sample was separated into different functionality fractions (see Fig. 38). The major fraction of the sample eluting between 14 and 25 min exhibited a partial oligomer separation. 

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