Lithium bromide crystal structure

Fig. 1.1. Crystal structure of lithium enolate of methyl -butyl ketone in a structure containing four Li+, two enolates, and one HMDA anions, one bromide ion, and two TMEDA ligands. Reproduced from Angew. Chem. Int. Ed. Engl., 35, 1322 (1996), by permission of Wiley-VCH.

Lithium bromide, LiBr, crystallizes in the NaCl face-centered cubic structure with a unit cell edge length of a = b = c = 5.501 A. Assume that the Br ions at the corners of the unit cell are in contact with those at the centers of the faces. Determine the ionic radius of the Br ion. One face of the unit cell is depicted in Figure 13-30. 

An extensive collection of both experimental and theoretical evidence suggests that the most accurate description of the ylide is one in which an easily pyramidalized carbanion is stabilized by an adjacent tetrahedral phosphonium center (25-34). These conclusions are supported by NMR studies and X-ray crystal structure determinations. Thus, increased electron density at the a-carbon of nonstabilized ylides is consistent with the upheld chemical shift in the NMR spectrum by comparison with the parent phosphonium salts (Table 3, entries 1-5) (26). However, the chemical shift by itself is not a reliable indicator of ylide structure. This is most clearly seen in some of the conjugated ylides, and also in entry 3, which differs from entry 1 only by the presence of lithium bromide. Both the lithium-free (1) and the lithium-containing ylides (3) have the same chemical shift, but they differ dramatically in the coupling constant. In entry 3,... 

Two other papers from this laboratory should also be mentioned. Ambrose, Elliott, and Temple (1951) have studied the infrared spectrum of a single crystal of diketopeperazine and obtained excellent confirmation of the structure worked out by Corey (1938) for this molecule by X-ray methods. Of particular interest is the conclusion that the three bonds of the nitrogen atom are coplanar in this molecule. The other publication (Ambrose, Bamford, Elliott, and Hanby, 1951) concerns the spectra of silk rendered soluble in water by treatment in a concentrated solution of lithium bromide. The soluble silk appears to be in the a (folded) configuration and becomes insoluble when it (or part of it) goes over to the 3 (extended) configuration. 

Recently, Barnea et al. reported the synthesis of Cp 2UMe2 by the reaction of Cp 2UCl2 with methyl lithium in presence of hthium bromide [254]. The crystal structure of Cp 2UMe2 (Fig. 20) was also found to have a similar type of geometry to that of Cp 2AnX2. 

A triple anion complex containing enolate, amide, and halide functionalities can be isolated from the mixture of n-butyl bromide, hexamethyldisilazane, TMEDA, Bu Li and pinacolone (Bu COMe). The resulting solution of LiBr, LiN(SiMc3)2, LiOC(Bu )=CH2, and TMEDA produces crystals of Li4(/.t4-Br)( u-OC(Bu )=CH2)2(M-N(SiMe3)2)(TMEDA)2, which, instead of forming a ladder-type structure, consists of a planar butterfly of four lithium atoms bonded to a //4-Br the stability of this arrangement has been studied with semi-empirical (PM3) and ab initio HE/ LANL2DZ computations. ... 

All the alkali metal halides except the cliloride, bromide and iodide of caesium form cubic crystals with the rock salt lattice and show a co-ordination number of 6. The exceptions are also cubic, but have the caesium chloride structure (Fig. 133) characterised by a co-ordination number of 8. The radius ratio for CsCl, Cs /Cl" = 0.93, allows 8 co-ordination, but is so near the ratio for 6 co-ordination that caesium chloride is dimorphous, changing, at 445°, from the caesium chloride to the rock salt structure. The crystalline halides are generally markedly ionic, though, as expected, lithium iodide is somewhat covalent, for iodide is the largest and most easily polarised simple anion and lithium, the smallest alkali metal cation, possesses the strongest polarising power. 

The application of a 11-ferrocenylundecyl-ammonium bromide/hexa-decylammonium bromide surfactant mixture as structure-directing agent resulted in a lamellar mesostructured silica film, which showed electronic conductivity due to electron transport in the ferrocenyl chains. Lyotropic lithium triflate-silicate liquid crystals have been utilized as supramolecular templates in the synthesis of ionically conducting nanocomposite films. ... 

For the preparation of MBM, the starting phenol was alkylated to 2-(n)-butoxy-1,4-dimethoxybenzene in methanolic KOH with n-butyl bromide. The benzaldehyde melted at 79.5-81 °C from methanol, and formed a malononitrile derivative that had a melting point of 134.5-135 C. The nitrostyrene from the aldehyde and nitroethane in acetic acid crystallized from methanol with a mp of 71-72 °C. Lithium aluminum hydride reduction in ether gave the ether-insoluble chloroform-soluble product 4-(n)-butoxy-2,5-dimethoxyamphetamine hydrochloride (MBM) with a melting point of 128-130 °C. This product met all tests for structural integrity, and assays were started. At levels of up to 12.0 milligrams, there were no effects noted. 

The synthesis of a new core structure of ferroelectric liquid crystals takes advantage of a transmetalation protocol (eq 58). The aryl bromide to phenol conversion is achieved via lithium-halogen exchange followed by trapping with B(OiProp)3 and subsequent peroxide oxidation in one pot. ... 

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