Lithium sulphides

The preparation of the alkali monosulphides.—Products usually called sulphides have been obtained by the direct union of the elements. Thus, L. Troost 2 prepared what he regarded as amorphous lithium sulphide, Li2S, by the action of sulphur vapour on heated lithium. H. Davy, and J. L. Gay Lussac and L. J. Thenard, prepared sodium sulphide, Na2S, by warming sulphur with sodium ... 

The low temp, form is the more expansible, and has the higher sp. ht. The specific gravity of crystalline lithium sulphide, according to A. Mourlot, ranges from l-63 to 1 70 E. Filhol gives 2-471 for sodium sulphide, and 2 13 for potassium sulphide— E. Filhol s numbers presumably refer to the hydrated salts. O. Boch s values for the sp. gr. of aq. soln. arq indicated below. 

It should be noted that several procedures are available for the preparation of l-(trimethylsilyloxy)cyclohexene. In an original report252 it was prepared by heating a dimethylformamide solution of cyclohexanone under reflux with chlorotrimethylsilane in the presence of triethylamine. This procedure is generally satisfactory for aldehydes and symmetrical ketones, or ketones which can enolise in one direction only. The method described in Expt 5.214 employs lithium sulphide as an additive to increase the silylating power of the chlorotrimethylsilane, so that the reaction proceeds at room temperature acetonitrile is used as the solvent.253... 

Notes. (1) Lithium sulphide is obtained from Alfa Ventron. Acetonitrile is purified and stored over molecular sieves. 

A poorly crystalline "rag" structure has been described for synthetic product obtained by the reaction between molybdic chloride and lithium sulphide in tetrahydrofuran. The product was purified by repeated washing with tetrahydrofuran to remove the lithium chloride. Heat treatment of the amorphous powder gave a low degree of crystallization. 

At room temperature in THF, hexamethyldisilthiane and methyl lithium give a soluble form of lithium sulphide which proves more reactive than the insoluble form which slowly precipitates on ageing. Thus 1,3-dihydroisothianaphthene results from the dibromide in 95% yield if prepared promptly, but in only 40% yield after 24 h ageing (equation 27)26. 

Relaxation and Electronic Structure of Surfaces in Lithium Sulphide a Hartree-Fock Ab Initio Approach. 

Determination of the pressure as a function of the combustion time is now mainly performed by means of piezoelectric pressure transducers. They operate such that the measured pressure that acts on their quartz-crystal measuring element via a diaphragm is transformed into a corresponding electric charge. After the electric charge is amplified, it is recorded by suitable measuring equipment. Quartz-crystal, barium titanate, and lithium sulphide can be used as the measuring elements in piezoelectric transducers. 

A new and efficient combination for silylation is trimethylsilyl chloride-lithium sulphide. Even hindered hydroxy-groups are silylated at room temperature in neutral conditions, although the mechanism of the process is not yet clear. 4-Dimethylaminopyridine (DMAP) has been shown to be an efficient catalyst for the silylation of alcohols by t-butyldimethylsilyl chloride and to be more selective than the imidazole traditionally used. Two new methods for removal of the t-butyldimethylsilyl group are treatment with boron trifluoride etherate and reaction with aqueous HF in acetonitrile. The O-silyl derivatives of normal carboxylic esters, i.e. keten methyl trialkylsilyl acetals (59), have been investigated in silyl transfer to alcohols (Scheme 31) they have the advantage of... 

Preparation.—It has recently been shown that the reaction of lithium tri-ethylborohydride with elemental sulphur in THF in the correct proportions [equation (15)] produces a solution believed to contain lithium sulphide, and which reacts with alkyl halides RX to give the dialkyl sulphides R2S in high yields. Commercially available Li2S is insoluble in THF, so the triethylborane produced here must play a role. 

Another step forward in this tectmology was obtained by changing the cathode from the common sulphur-carbon composite to a lithium sulphide-carbon composite [51]. In this way, the cathode becomes tiie lithium ion source, allowing replacement of the reactive lithium metal with other more reliable lithium-accepting material, thus obtaining a metal-free, lithium-ion sulphur battery. This concept was first demonstrated by using a tin-carbon anode [52,53] and... 

These results consistently contributed to improvements in the technology of lithium/sulphur battery however, some residual issues still remain to prevent full practical application of this high-energy battery system. Most of the recent works rely on conventional liquid organic carbonate solution as the preferred electrolyte although the sulphur and/or the lithium sulphide are shielded into a carbon matrix, either mesoporous [46] or spherical [50], thus in principle preventing the direct contact with the electrolyte, it is not yet fully established whether the solubility of the polysulphides is effectively blocked. Another issue still to be solved is in the relatively modest power capability of these batteries. 

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