Lithium disulphide

Rajanikanth and Ravindranath44 have recently published a deoxygenation reaction for sulphoxides that uses metallic lithium in refluxing dimethoxyethane. Dialkyl and alkyl phenyl sulphoxides were reduced cleanly in yields around 70%, even if sterically hindered, but benzyl sulphoxides gave mixtures of products. For example, benzyl phenyl sulphoxide gave frans-stilbene (33%), benzyl phenyl sulphide (20%) and diphenyl disulphide (47%). These products can be rationalized by reaction pathways such as in equation (17) ... 

Brandsma and coworkers were able to show that meta- (59a) and para-dilithiated benzene (59b) are accessible via iodine-lithium exchange, using n-butyllithium. Therefore, 1,3- and 1,4-diiodobenzene (58a and 58b) respectively were reacted with two equivalents of n-butyllithium in diethyl ether at low temperatures (Scheme 21). The polyUthiation was confirmed by trapping reactions with dimethyl disulphide. The same reactions, starting from the corresponding dibromobenzenes, had led only to monolithiated benzenes. 

The commercially most important voltage compatible lithium primary cell uses iron disulphide, FeS2, as cathode. The overall cell reaction may be written as... 

Historically the most commonly used lithium intercalation compound was titanium disulphide, TiS2- This compound has a layered structure of covalently bound S-Ti-S stacks held together by weak van der Waals forces. Each stack is formed by a layer of titanium atoms between two layers of sulphur atoms in a hexagon ally close packed arrangement, Lithium ions can be readily intercalated between the stacks, and if the intercalation level x is maintained below unity, the process induces only a modest and reversible expansion along the c axis (Fig. 7.13). The electrochemical reaction of the Li/TiS2 couple... 

This battery was based on a lithium metal anode and a molybdenum disulphide cathode ... 

The electrochemical discharge-charge process of the battery is based on the intercalation/de-intercalation of lithium molybdenum disulphide ... 

Fig. 9.25 Cross-section of 0.5 A, 28 V lithium-iron disulphide 60 minute thermal batlery. The battery contains 15 active cells and has a total volume of 400 cm3. (By courtesy of Sandia National Laboratories.)...

Lithium polysulphides-—Fusion of lithium hydroxide with sulphur yields a yellow mass like liver of sulphur, probably consisting of polysulphides of lithium. Berzelius isolated a hydrated disulphide, Li2S2, iH20, by concentrating an aqueous solution of the monosulphide. 

Table 13.6 Typical Load-Carrying Capacity Figures for Lithium Soap Greases With and Without Molybdenum Disulphide ( Mean figures from several publications.)...

The best performance found in the Climax Molybdenum Company test programme was for a lithium hydroxystearate soap-thickened grease with a conventional EP additive and 10% by weight of molybdenum disulphide with a nominal particle size of 7.0 jum. This grease had a Timken OK Load of 23 lbs (10.5 kg), Falex load capacity of 1450 lbs (658 kg). Mean Hertz Load of 90.5 and Weld Load of 630 kg. 

The monosulphide and polysulphides are formed by burning the metals in sulphur vapour, by the action of sulphur on the metals dissolved in liquid ammonia, and by the action of the molten metals on sulphur dissolved in toluene. Hydrates or alcoholates and, in some cases, the anhydrous compounds may be prepared by dissolving sulphur in hot solutions of the hydrosulphides or monosulphides. Potassium, rubidium and caesium give all the sulphides where = 1, 2, 3, 4, 5, or 6 sodium only up to the pentasulphide, and lithium only those for which x = 1, 2 and 4 (Pearson and Robinson, 1931). All the metals form two polysulphides of relatively outstanding stability one is invariably the disulphide, and the other tetrasulphide in the case of lithium or sodium, and pentasulphide in the case of potassium, rubidium or caesium. The amount of water of crystallisation and the solubility decrease with increase in atomic number of the metal, the gradation being most marked between sodium and potassium. 

It was assumed that disulphide bond breakdown was a prerequisite for supercontraction. Later work by Elod and Zahn Melliand Textilber, 1949, 30,17) and others has thrown doubt upon the assumption because phenols, formamide, and lithium bromide can all cause supercontraction, and it is well known that they have no effect upon the cystine sulphur. Lithium bromide, in particular, as well as the others, is capable of dissociating hydrogen bonds which points to the probability that the latter are involved. 

Organometallic Derivatives of Monocyclic Thiophens - Lithium. Numerous a-substituted thiophens have been prepared via metallation of thiophens with organolithium derivatives. Thus 2-thienyl-lithium has been allowed to react with tetraisopropylthiuram disulphide to give 5-(2-thienyl) A(,A -di-isopropyl-dithiocarbamate in quantitative yield. ° Through the reaction of 2-thienyl-lithium with tellurium in THF, the tellurolate was obtained, which was converted into various products. The reaction of 2-thienyl-lithium with 1,1-dichloro-2,2-difluoroethene has been developed into a very useful method for... 

The halogen-metal exchange between 4-iodo-2-methoxythiophen and butyl-lithium, followed by reaction with dimethyl disulphide, carbon dioxide, or DMF, was used for the synthesis of various 4-substituted 2-methoxythio-phens. In connection with work on optically active 3-(cyclohexenyl)-thiophens, substituted 3-thienyl-lithium derivatives were allowed to react with cyclohexanones and cyclohexenones. The reaction of 3,4-dibromothiophen with two equivalents of butyl-Hthium and sulphur, followed by CS2, was used for the synthesis of (96), an intermediate for the synthesis of the organic metals (97). ... 

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