Lithium ethers

Starting material Lithium Ether in ml Product Yields b.p. °C/Torr... 

Note 6) so that the freshly cut lithium pieces drop directly into the anhydrous ether. 1,4-Dichlorobutane (33.5 mL, 300 mmol) (Note 2) is then dissolved in anhydrous diethyl ether (85 mL) and introduced into the addition funnel approximately 10% of this solution is introduced into the lithium/ether suspension, and the reaction is initiated by vigorous stirring. A white precipitate (LiCI) signaling initiation of the reaction should be apparent within 5 to 15 min, at which time the remainder of the solution is added dropwise over a 1 to 2-hr period (Note 7). The white suspension is rapidly stirred for 20 hr at 0°C. 

Monomer synthesis. Dichloro[p-(S)-2-methylbutylphenyl](p- -butylphenyl)si-lane (1) is prepared by lithiation of p-(S)-2-methylbutylphenylbromide in dry diethylether at 0 °C. The resulting aryl lithium ether solution is added to an equimolar amount of trichloro(p-n-butylphenyl)silane (prepared by addition of p-M-butylphenyl lithium to silicon tetrachloride) in dry -hexane (Chart 13.24). 

LiAlH4, lithium tetrahydridoaluminate ("lithium aluminium hydride . so-called) is an excellent reducing agent in ether solution for both organic and inorganic compounds it may be used to prepare covalent hydrides SiH ether, for example... 

Boron forms a whole series of hydrides. The simplest of these is diborane, BjH. It may be prepared by the reduction of boron trichloride in ether by lithium aluminium hydride. This is a general method for the preparation of non-metallic hydrides. 

There is one other important way in which borane can be stabilised. Diborane reacts with a suspension of lithium hydride in dry ether thus... 

When lithium hydride is allowed to react with aluminium chloride in ether solution, two reactions occur ... 

Silicon, unlike carbon, does notiorm a very large number of hydrides. A series of covalently bonded volatile hydrides called silanes analogous to the alkane hydrocarbons is known, with the general formula Si H2 + 2- I uf less than ten members of the series have so far been prepared. Mono- and disilanes are more readily prepared by the reaction of the corresponding silicon chloride with lithium aluminium hydride in ether ... 

Pure phosphine can be prepared by the reduction of a solution of phosphorus trichloride in dry ether with lithium aluminium hydride ... 

Lithium aluminium hydride if carelessly manipulated may be dangerous for two distinct reasons. The material is caustic, and should not be allowed to touch the skin it is particularly important that the finely divided material should be kept away from the lips, nostrils and eyes, and consequently pulverisation in a mortar must be carried out with the mortar in a fume-cupboard, and with the window drawn down as far as possible in front of the operator. This danger from handling has however been greatly reduced, for the hydride is now sold in stated amounts as a coarse powder enclosed in a polythene bag in a metal container this powder dissolves readily in ether, and preliminary pulverisation is unnecessary. 

Required Salicylic acid, 6 0 g. lithium aluminium hydride, 2 5 g. dry ether, 165 ml. 

Lithium aluminium hydride LiAlH is a useful and conveuient reagent for the selective reduction of the carbonyl group and of various other polar functional groups. It is obtained by treatment of finely powdered lithium hydride with an ethereal solution of anhydrous aluminium chloride ... 

Many organolithium compounds may be prepared by the interaction of lithium with an alkyl chloride or bromide or with an aryl bromide in dry ethereal solution In a nitrogen atmosphere ... 

The lithium may also be pressed into wire of about 0-5 mm. diameter a rather Sturdy press is necessary. The wire may be collected directly in sodium - dried ether. 

The stability of the various cumulenic anions depends to a large extent upon the nature of the groups linked to the cumulenic system. Whereas solutions of lithiated allenic ethers and sulfides in diethyl ether or THF can be kept for a limited period at about O C, the lithiated hydrocarbons LiCH=C=CH-R are transformed into the isomeric lithium acetylides at temperatures above about -20 C, probably via HC C-C(Li )R R Lithiated 1,2,4-trienes, LiCH=C=C-C=C-, are... 

In the flask were placed 800 ml (note 1) of dry diethyl ether. Twenty grams of lithium (note 2) were flattened (thickness about 1 mm) with a hammer (note 3) and cut into small pieces (about 10 x 2 1 mm ), which were introduced at the same time into the flask. The contents of the flask were cooled to -30°C, after the air in the flask had been replaced with nitrogen. From the dropping funnel, which contained 1.12 mol of ethyl bromide, were added 10-15 g of ethyl bromide. 

It took 5-10 min before the reaction started this was visible by the appearance of turbidity of the diethyl ether and later by the appearance of a gloss on the pieces of lithium and a distinct increase in temperature. Care was taken that the temperature did not rise above -20°C (note 4). When the reaction had subsided, the addition of ethyl bromide was continued, now dropwise (note 5). The temperature was kept between -20 and -30 C (note 6). After the addition, which was carried out in 30-40 min, stirring was continued for about a further 1 h. The temperature was allowed to rise gradually to -10°C. When the gloss on the piece of lithium had disappeared, the solution was poured into another flask through... 

The lithiation of allene can also be carried out with ethyllithium or butyl-lithium in diethyl ether (prepared from the alkyl bromides), using THF as a cosolvent. The salt suspension which is initially present when the solution of alkyllithium is cooled to -50°C or lower has disappeared almost completely when the reaction between allene and alkyllithium is finished. 

A mixture of 0.40 mol of propargyl chloride and 150ml of dry diethyl ether was cooled at -90°C (liquid nitrogen bath) and a solution of 0.40 mol of ethyl-lithium (note 1) in about 350 ml of diethyl ether (see Exp. 1) was added with vigorous stirring and occasional cooling (note 2). The temperature of the reaction mixture was kept between -70 and -90°C. The formation of the lithium derivative proceeded almost instantaneously, so that the solution obtained could be used directly after the addition of the ethyl 1ithium, which was carried out in 15-20 min. This lithium acetylide solution is very unstable and must be kept below -60°C. 

Exp. 4) in 10 min with cooling at -30°C. After an additional 15 min 0.30 mol of a-chlororaethyl ethyl ether (note 2) was introduced in 10 min, while keeping the temperature between -20 and -30°C. A white precipitate of lithium chloride was formed. The cooling bath was then removed and the temperature was allowed to rise to +10°C. The mixture was hydrolyzed by shaking it with 200 ml of a solution of 30 g of ammonium chloride, to which 5 ml of aqueous ammonia had been added. 

Hate 1. To a suspension of 0.40 mol of lithium amide in 400 ml of liquid NH3 (see Chapter II, Exp. 11) was added 0.30 mol of HCECCH20-tert.-CitHg Subsequently 0.46 mol of CjHsBr was introduced in 30 min. After an additional 1 h the NH3 was removed by placing the flask in a water-bath at 40°C. Addition of water, extraction with diethyl ether and distillation gave C2H C=CCH20-tert.-C,H in more than 85% yield. 

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