Metal deuterium

Finally, the configuration of the water (D20) molecule with respect to the metal ion can be probed by neutron diffraction methods. These give metal-deuterium distances which, when compared with metal-oxygen distances, give the angle between the plane of the water (D20) and the M—O bond. This is 55° for Nd3+ 193 it is said to vary with concentration for Ni2+ in solution.189... 

Estimated errors are given within parentheses. The derived metal-oxygen, M—O, and metal-deuterium, M—D, distances are given in angstroms. The tilt angle is defined as the angle between the M—O bond and the plane of the water molecule. 

The diameter of the octahedral void is 0.4142 a0 and that of the tetrahedral void 0.2247 a0, where a0 is the distance of nearest approach of atoms in the unit cell. With a0 = 3.227 A. for the hexagonal unit cell of a-Zi, the diameter of the bonded atom which can be accommodated in the octahedral void would be 1.336 A. and in the tetrahedral void 0.725 A. The diameters of the bonded deuterium atoms as derived from the nearest metal-metal and metal-deuterium atom distances in the crystal structures of each of the deuteride phases on the other hand are as given in Table VI. 

A covalent metal - deuterium bond creates a strong non - homogeneous electric field along the M - D direction (the Z axis). One of the important parameters, describing the electric field, is the magnitude of the EFG at the D... 

Syntheses of [ rf-CsHs)WiC0)3S02CH2D and l(Ph3P)Mn(CO)4S02CH3] that involve the insertion of sulphene into the metal-deuterium and the metal-hydrogen bond have been reported. 

Process 2, the adsorption of the reactant(s), is often quite rapid for nonporous adsorbents, but not necessarily so it appears to be the rate-limiting step for the water-gas reaction, CO + HjO = CO2 + H2, on Cu(lll) [200]. On the other hand, process 4, the desorption of products, must always be activated at least by Q, the heat of adsorption, and is much more apt to be slow. In fact, because of this expectation, certain seemingly paradoxical situations have arisen. For example, the catalyzed exchange between hydrogen and deuterium on metal surfaces may be quite rapid at temperatures well below room temperature and under circumstances such that the rate of desorption of the product HD appeared to be so slow that the observed reaction should not have been able to occur To be more specific, the originally proposed mechanism, due to Bonhoeffer and Farkas [201], was that of Eq. XVIII-32. That is. 

Two types of hydrogen replacement are discussed here (1) the base-induced hydrogen-deuterium exchange reactions and (2) the hydrogen-metal exchange reactions. 

In the spring of 1989, it was announced that electrochemists at the University of Utah had produced a sustained nuclear fusion reaction at room temperature, using simple equipment available in any high school laboratory. The process, referred to as cold fusion, consists of loading deuterium into pieces of palladium metal by electrolysis of heavy water, E)20, thereby developing a sufficiently large density of deuterium nuclei in the metal lattice to cause fusion between these nuclei to occur. These results have proven extremely difficult to confirm (20,21). Neutrons usually have not been detected in cold fusion experiments, so that the D-D fusion reaction familiar to nuclear physicists does not seem to be the explanation for the experimental results, which typically involve the release of heat and sometimes gamma rays. 

The stereochemistry of hydrogen-deuterium exchange at the chiral carbon in 2-phenylbutane shows a similar trend. When potassium t-butoxide is used as the base, the exchange occurs with retention of configuration in r-butanol, but racemization occurs in DMSO. The retention of configuration is visualized as occurring through an ion pair in which a solvent molecule coordinated to the metal ion acts as the proton donor... 

Two techniques, electrochemical reduction (section IIl-C) and Clem-mensen reduction (section ITI-D), have previously been recommended for the direct reduction of isolated ketones to hydrocarbons. Since the applicability of these methods is limited to compounds which can withstand strongly acidic reaction conditions or to cases where isotope scrambling is not a problem, it is desirable to provide milder alternative procedures. Two of the methods discussed in this section, desulfurization of mercaptal derivatives with deuterated Raney nickel (section IV-A) and metal deuteride reduction of tosylhydrazone derivatives (section IV-B), permit the replacement of a carbonyl oxygen by deuterium under neutral or alkaline conditions. 

The metal-bound deuteriums in (133) react readily with olefins which enter... 

Deuterioboration is one of the most important recent additions to the array of methods for saturating double bonds with deuterium. The easy accessibility of metal deuterides (lithium aluminum deuteride or sodium borodeuteride) facilitates the in situ preparation of deuteriodiborane which reacts with steroidal double bonds with a high degree of site and/or stereospecificity, depending on the location of the double bond. " ... 

In the past few years metal deuterides have become commercially available at reasonable prices. This has encouraged the use of these reagents for reactions involving deuteride displacements of suitable leaving groups. The attractive feature of these reactions is the stereospecificity of the deuterium insertion. 

During an attempt to metalate a glycal with /-BuLi, it was discovered by deuterium labeling that a TBDMS ether can be deprotonated. °- ... 

The photo-Kolbe reaction is the decarboxylation of carboxylic acids at tow voltage under irradiation at semiconductor anodes (TiO ), that are partially doped with metals, e.g. platinum [343, 344]. On semiconductor powders the dominant product is a hydrocarbon by substitution of the carboxylate group for hydrogen (Eq. 41), whereas on an n-TiOj single crystal in the oxidation of acetic acid the formation of ethane besides methane could be observed [345, 346]. Dependent on the kind of semiconductor, the adsorbed metal, and the pH of the solution the extent of alkyl coupling versus reduction to the hydrocarbon can be controlled to some extent [346]. The intermediacy of alkyl radicals has been demonstrated by ESR-spectroscopy [347], that of the alkyl anion by deuterium incorporation [344]. With vicinal diacids the mono- or bisdecarboxylation can be controlled by the light flux [348]. Adipic acid yielded butane [349] with levulinic acid the products of decarboxylation, methyl ethyl-... 

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