Lithium sublimation

Sublimation of solid lithium. Sublimation involves taking a substance from the solid state to the gaseous state ... 

Anionic polymerization of vinyl monomers can be effected with a variety of organometaUic compounds alkyllithium compounds are the most useful class (1,33—35). A variety of simple alkyllithium compounds are available commercially. Most simple alkyllithium compounds are soluble in hydrocarbon solvents such as hexane and cyclohexane and they can be prepared by reaction of the corresponding alkyl chlorides with lithium metal. Methyllithium [917-54-4] and phenyllithium [591-51-5] are available in diethyl ether and cyclohexane—ether solutions, respectively, because they are not soluble in hydrocarbon solvents vinyllithium [917-57-7] and allyllithium [3052-45-7] are also insoluble in hydrocarbon solutions and can only be prepared in ether solutions (38,39). Hydrocarbon-soluble alkyllithium initiators are used directiy to initiate polymerization of styrene and diene monomers quantitatively one unique aspect of hthium-based initiators in hydrocarbon solution is that elastomeric polydienes with high 1,4-microstmcture are obtained (1,24,33—37). Certain alkyllithium compounds can be purified by recrystallization (ethyllithium), sublimation (ethyllithium, /-butyUithium [594-19-4] isopropyllithium [2417-93-8] or distillation (j -butyUithium) (40,41). Unfortunately, / -butyUithium is noncrystaUine and too high boiling to be purified by distiUation (38). Since methyllithium and phenyllithium are crystalline soUds which are insoluble in hydrocarbon solution, they can be precipitated into these solutions and then redissolved in appropriate polar solvents (42,43). OrganometaUic compounds of other alkaU metals are insoluble in hydrocarbon solution and possess negligible vapor pressures as expected for salt-like compounds. 

The corresponding tellurium diimide BuNTe( -N Bu)2TeN Bu (10.7) may be obtained in good yields from the reaction of lithium tert-butylamide with TeCU in THE (Eq. 10.3). °" In toluene solution this reaction also produces the cyclic tellurium(II) imide (TcN Bu)3. The dimer 10.7 is obtained as an orange solid, which can be purified by vacuum sublimation at ca. 90°C. 

In a similar manner, treatment of anhydrous rare-earth chlorides with 3 equivalents of lithium 1,3-di-ferf-butylacetamidinate (prepared in situ from di-ferf-butylcarbodiimide and methyllithium) in THF at room temperature afforded LnlMeCfNBuOils (Ln = Y, La, Ce, Nd, Eu, Er, Lu) in 57-72% isolated yields. X-ray crystal structures of these complexes demonstrated monomeric formulations with distorted octahedral geometry about the lanthanide(III) ions (Figure 20, Ln = La). The new complexes are thermally stable at >300°C, and sublime... 

The reaction of the crowded stibole 53 and bismole 54 with lithium followed by addition of lithium cyclopentadienide (Scheme 9) gives mixtures of the corresponding monostibaferrocene 69 and monobismaferro-cene 70, respectively, with ferrocene.25 The more volatile ferrocene is easily removed by sublimation. Rather small amounts of the crowded diheteroferrocenes 55 or 56 are formed in this reaction. 

Unfortunately, both the lithium and the sodium compound are stable even when melted, destilled or sublimed. Therefore, Si-O four-membered ring systems are not accessible by this method of synthesis up to now. 

The iron(II) chloride7 is prepared from 1.5 g. (0.0268 mol) of iron powder (hydrogen-reduced, 100-mesh), 6.0 g. (0.370 mol) of anhydrous sublimed iron(III) chloride (Matheson, Coleman and Bell, reagent-grade), and 150 ml. of tetrahydrofuran (THF) freshly distilled under nitrogen from lithium tetrahydroaluminate or preferably calcium hydride. 

The enthalpy of reaction 2.45 cannot be determined directly. As shown in figure 2.5, it is calculated by using several experimental quantities the standard enthalpy of formation of the solid alkoxide, the standard sublimation enthalpy and the ionization energy of lithium, and the standard enthalpy of formation and the adiabatic electron affinity of gaseous methoxy radical (equation 2.47). 

Styrene, benzene, and tetrahydrofuran were purified as described previously (8,11). Solutions of ec-butyllithium (Lithium Corporation of America, 12.0 wt % in cyclohexane) and methyllithium (Alfa, 1.45 M in ether) and lithium naphthalene were analyzed using the double titration procedure with 1,2-dibromoethane (12). Lithium naphthalene was prepared in tetrahydrofuran from lithium metal and a 25 mole % excess of sublimed naphthalene at -25°C using standard high vacuum procedures. Sealed ampoules of lithium naphthalene were stored in liquid nitrogen. 

A mixture of 1.0 g (27 mmol) of RUCI3 MH2O, 2.0 g (27 mmol) of lithium carbonate, and 0.66 g (10 mmol) of freshly distilled cyclopentadiene is heated at reflux in 50 mL of isopropanol for 16 h in a 100-mL round-bottomed flask with a standard tapered joint. The solvent is evaporated under reduced pressure, and the flask is connected to a short straight water-cooled reflux condenser (Fig. 1). The compound is sublimed at 80°C and 10 bar and collected from the bottom of the condenser. Yield 0.88 g (95%) of off-white crystals. 

The b.p. indicated above are by L. H. Borgstrom W. R. Mott gave 1300° and 1200° respectively for the b.p. of potassium and sodium chlorides. Lithium, sodium, and potassium chlorides begin to sublime at their m.p.,15 and probably alto the other salts as well. 

According to B. Schindler,16 potassium iodide volatilizes in free air when heated to the softening temp, of hard glass, and, according to B. Bunsen, and T. H. Norton and D. M. Both, it volatilizes from 0-352 to 0-423 times as fast as the same quantity of sodium chloride when heated in the hottest part of a Bunsen s flame. According to J. Dewar and A. Scott,17 the vapour density of potassium iodide is 169 8. A. von Weinberg obtained 43"3 Cals, for the heat of sublimation of sodium iodide, and 44 9 Cals, for that of potassium iodide and A. Beis obtained for sodium and potassium iodides respectively 51 and 46 Cals., and between 15 and 35 Cals, for lithium iodide. 

This very high compressibility is to be expected from the structure of the crystal which, as seen above, is molecular rather than ionic and moreover contains large open spaces between the atoms. The refractive indices at 17° C. are 1-733 for sodium light and 1-748 for lithium light.2 Klocke observed 3 that for yellow light the sublimed crystals exhibit double refraction, but this could not be confirmed by Brauns.4... 

The cooling bath is removed, and the mixture is left to reach room temperature with an air bath and stirred for 30 min. The solvent is removed under vacuum to afford a brown solid and then 30 mL of petroleum ether (40-60°C), freshly distilled from Na/benzophenone under nitrogen, is added to the flask. The dark yellow suspension is filtered to remove the lithium acetylacetonate, and the solid is washed twice with 7 mL of petroleum ether. The solvent is removed from the filtrate under vacuum to yield a dark yellow solid (1.95 g), which is sublimed at 50-60°C (10 3torr). The product is a yellow crystalline solid. Yield 1.84 g (86%). ... 

The alkylltlhium compounds are usually colorless, soluble in organic solvents, and capable of distillation or sublimation. They are nonelec -trolyies and are widely used in synthetic organic chemistry, since, like other lithium compounds, they resemble in their properties the corresponding magnesium compounds. 

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