Lithium and Boron

Since hthium and boron isotope fractionations mainly occur during low temperature processes, Li and B isotopes may provide a robust tracer of surface material that is recycled to the mantle (Elhott et al. 2004). Heterogeneous distribution of subducted oceanic and continental crust in the mantle will thus result in variations in Li and B isotope ratios. Furthermore, dehydration processes active in subducdon zones appear to be of crucial importance in the control of Li and B isotope composition of different parts of the mantle. For the upper mantle as a whole Jeffcoate et al. (2007) gave an estimated 8 Li-value of 3.5%o. 

Since boron concentrations in mantle minerals are exceedingly low, boron isotope analysis of mantle minerals are very restricted. On the basis of a boron budget between mantle and crust, Chaussidon and Marty (1995) conclnded that the primitive mantle had a 5 B-value of-10 2%c.ForMORB Spivack and Edmond (1987) and Chaussidon and Marty (1995) reported a 5 B-value of aronnd -4%c. Higher and lower 5 B-values observed in some ocean island basalts shonld be due to crustal assimilation (Tanaka and Nakamura 2005). 

On the basis of their high temperature of formation, it could be expected that magmatic rocks exhibit relatively small differences in isotopic composition. However, as a resnlt of secondary alteration processes and the fact, that magmas can have a crnstal and a mantle origin, the variation observed in isotopic composition of magmatic rocks can actnally be quite large. 

Provided an igneous rock has not been affected by subsolidus isotope exchange or hydrothermal alteration, its isotope composition will be determined by  

The isotope composition of the source region in which the magma was generated 

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Values are for normal power operation. Conductivity, pH, and concentrations of lithium and boron are plant specific and vary over the fuel cycle according to the control scheme used. See Fig. 3. 

The main metals in brines throughout the world are sodium, magnesium, calcium, and potassium. Other metals, such as lithium and boron, are found in lesser amounts. The main nonmetals ate chloride, sulfate, and carbonate, with nitrate occurring in a few isolated areas. A significant fraction of sodium nitrate and potassium nitrate comes from these isolated deposits. Other nonmetals produced from brine ate bromine and iodine. 

Application of this transition state analysis to the reactions of lithium and boron propionate cno-lates and a-methyl chiral aldehydes ... 

Reaction conditions that involve other enolate derivatives as nucleophiles have been developed, including boron enolates and enolates with titanium, tin, or zirconium as the metal. These systems are discussed in detail in the sections that follow, and in Section 2.1.2.5, we discuss reactions that involve covalent enolate equivalents, particularly silyl enol ethers. Scheme 2.1 illustrates some of the procedures that have been developed. A variety of carbon nucleophiles are represented in Scheme 2.1, including lithium and boron enolates, as well as titanium and tin derivatives, but in... 

Sahoo SK, Masuda A (1995) Simultaneous measurement of lithium and boron isotopes as lithium tetraborate ion by thermal ionization mass-spedrometry. Analyst 120 335-339... 

Several elements from the multielement suite are associated with alteration and clay chemistry. Due to the relative cleanliness of the Athabasca Group sandstones, anomalous contents of aluminium, magnesium, potassium, lithium, and boron, along with loss-on-ignition, provide measures of the amount and type of alteration present. These data... 

Figure 5.45 Two possible mechanism for the hydrogen absorption by lithium and boron to form LiBH4.

Analysis of results for a-substituted aldehydes with E- and Z-enolates indicates that the cyclic transition states shown below are favored with lithium and boron enolates.64a... 

A lack of water in parts of Argentina explains why sulfide oxidation and mine drainage contribute little to the maximum 0.140mgL 1 of arsenic in local surface waters (Williams, 2001, 274). The sodium chloride-dominated waters are rich in lithium and boron, which suggests that the arsenic is associated with the dissolution of salt deposits rather than sulfide weathering (Williams, 2001, 274). Excessive evaporation in arid climates would initially concentrate arsenic in briny lake water and eventually precipitate it in salt... 

Tris(N-methylanilino)borane has previously been prepared by the reaction of boron trifluoride-ether complexes with three equivalents each of N-methylaniline and a suitable Grignard reagent,1,2 by the reaction of (N-methylanilino)potassium with boron trifluoride-ether complexes,2 and by aminolysis of boron trichloride by N-methylaniline.3 The present general procedure describes a convenient preparation of tris(N-methylanilino)-borane by the reaction of (N-methylanilino)lithium and boron trifluoride-diethyl ether in tetrahydrofuran-hexane as solvent. 

Seyfried W. E., Janecky D. R., and Mottl M. J. (1984) Alteration of the oceanic crust implications for geochemical cycles of lithium and boron. Geochim. Cosmochim. Acta 48, 557-569. 

Structure of a dinuclear heterometallic methoxide derivative containing lithium and boron, (MeOH)2Li(/x-OMe)2B(OMe)2 (Fig. 13), was detemiined by the X-ray diffraction method (124) both lithium and boron atoms were found to be four coordinate. 

Combining the fusion technique with ICPES measurements gives a rapid and accurate method for the ash elemental analysis. The total analysis time needed is 20-25 minutes per sample. However, although the fusion procedure is excellent for the determination of all major elements, it is not suitable for the determination of trace elements, because the final solution (1 L) is too dilute for detection of trace elements. If the solution volume is kept small, extremely high concentrations of lithium and boron in the solution give an undesirable high background spectrum for trace element measurements. Hence, it is necessary to resort to a separate procedure where both trace and major elements can be simultaneously determined. 

A voltage is then applied, also at an elevated temperature, to opposite faces, positive on the n side and negative on the p side (called reverse bias ). This causes the Li ions to drift toward the p side, resulting in a wide central region of constant lithium concentration this region is now intrinsic because it has equal lithium and boron concentrations. 

Popovici, G. Melnikov, A. Varichenko, V.V. Sung, T. Prelas, M.A. Wilson, R.G. Loyalka, S.K. Diamond ultraviolet photovoltaic cell obtained by lithium and boron doping. J. Appl. Phys. 1997, 81 (5), 2429-2431. 

One of the more useful chiral auxiliaries that has been developed is illustrated in equation (128). The lithium enolates of imides (229) react with aldehydes to give mainly the syn diastereomer (230), along with (231) and an anti isomer (Table 27). After purification, the major syn isomer is obtained in good yield and in good stereochemical purity. The results shown in Table 27 nicely complement the results obtained using the boron enolate. In this case, no anti products are observed and the (231) (230) ratio is >9S S in all cases. Thus, acylsultam (229), like a-alkoxy ketone (181 Scheme 11), has opposite diastereofacial preference as its lithium and boron enolates. 

For a thorough analysis of stereoselective aldol additions of achiral lithium and boron enolates to chiral aldehydes, see ref. [123]. 

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