Lithium iodide, anhydrous

Lithium Iodide. Lithium iodide [10377-51 -2/, Lil, is the most difficult lithium halide to prepare and has few appHcations. Aqueous solutions of the salt can be prepared by carehil neutralization of hydroiodic acid with lithium carbonate or lithium hydroxide. Concentration of the aqueous solution leads successively to the trihydrate [7790-22-9] dihydrate [17023-25-5] and monohydrate [17023-24 ] which melt congmendy at 75, 79, and 130°C, respectively. The anhydrous salt can be obtained by carehil removal of water under vacuum, but because of the strong tendency to oxidize and eliminate iodine which occurs on heating the salt ia air, it is often prepared from reactions of lithium metal or lithium hydride with iodine ia organic solvents. The salt is extremely soluble ia water (62.6 wt % at 25°C) (59) and the solutions have extremely low vapor pressures (60). Lithium iodide is used as an electrolyte ia selected lithium battery appHcations, where it is formed in situ from reaction of lithium metal with iodine. It can also be a component of low melting molten salts and as a catalyst ia aldol condensations. 

Materials. Methyl methacrylate was a product of Rohm and Haas, and t-butyl methacrylate was obtained from Polvsciences, Inc. Potassium trimethylsilanolate (PTMS) was obtained from Petrarch Systems, Inc. Anhydrous lithium iodide, trimethylsilyl iodide (TMSI), and n-butyllit.ium (in hexanes) were purchased from Aldrich Chemical Co. 

Treatment of 146 with lithium in anhydrous liquid ammonia/1,2-dimethoxyethane, followed by addition of methyl iodide gives ester 147 in 72% yield. This sequence of reactions allows the highly stereoselective achievement of the metoxycarbonile group s axial stereochemistry in position 4. The synthesis of intermediates 148 and 149 is carried out using conventional methods. 

The melting point of anhydrous lithium iodide is 430°, according to W. Ramsay and N. Eumorfopoulos,15 446° 3 5° according to T. Carnelley, and 440° according to G. Scarpa. The first named also give 663° for the m.p. of sodium iodide ... 

Aldol condensation. Anhydrous lithium iodide (ca. 5 equivalents) promotes aldol condensation of ketones with enolizable or nonenolizable aldehydes. The intermediate aldol is usually not isolable, but can be intercepted by addition of ClSi(CH3)3 and N(C2H5)3. In this case Lil can be used in a catalytic amount. The salt cannot be replaced by LiBror LiCl or Nal. 

Lithium iodide, Lil.—On evaporation of the solution obtained by the interaction of lithium carbonate and hydriodic acid, or barium or calcium iodide, lithium iodide crystallizes in the form of hydrates,7 a trihydrate, dihydrate, and monohydrate having been isolated. Above 300° C. the anhydrous salt is formed, but its action on glass and porcelain at high temperatures has prevented its preparation in the pure state. The boiling-point of the iodide is 1170° C.,8 and the vapour-pressure in atmospheres corresponds with the expression... 

The basic organometallic reaction cycle for the Rh/I catalyzed carbonylation of methyl acetate is the same as for methanol carbonylation. However some differences arise due to the absence of water in the anhydrous process. As described in Section 4.2.4, the Monsanto acetic acid process employs quite high water concentrations to maintain catalyst stability and activity, since at low water levels the catalyst tends to convert into an inactive Rh(III) form. An alternative strategy, employed in anhydrous methyl acetate carbonylation, is to use iodide salts as promoters/stabilizers. The Eastman process uses a substantial concentration of lithium iodide, whereas a quaternary ammonium iodide is used by BP in their combined acetic acid/anhydride process. The iodide salt is thought to aid catalysis by acting as an alternative source of iodide (in addition to HI) for activation of the methyl acetate substrate (Equation 17) ... 

Redactiaa of at-luMteUmes Treatment of x-bromoketones with lithium iodide and boron trifluoride in ether or THF at room temperature affords the parent ketone in high yield. The hydrogen was eventually found to originate, presumably as water, in the lithium iodide (Alfa Inorganics, anhydrous ). Only one exception to the reduction was observed, namely a-bromocamphor failed to react. The procedure is also effective for some x-chloroketones (phenacyl chloride, 2-chloropentanone), but fail.s for hindered chloroketones (oi-chloronorbomanone). 

Several esters highly resistant to hydrolysis by base have been hydrolyzed successfully by refluxing with anhydrous lithium iodide in collidine. The reaction is often slow, for example, hydrolysis of the ester (1) required refluxing under nitrogen... 

Taschner and Liberek found that ester and N-carbomethoxy groups can be cleaved efficiently with anhydrous lithium iodide in refluxing pyridine. N-Acyl and peptide bonds do not react. Having experienced difficulty in hydrolyzing the... 

Whereas anhydrous lithium iodide in a refluxing base of suitable boiling point cleaves esters to the corresponding acids, lithium iodide dihydrate effects cleavage and concomitant decarboxylation, as illustrated for the case of 2-benzyl-2-carbo-methoxycyclopentanone. Elsinger refluxed a mixture of this keto ester, lithium... 

Epoxybicyclo[3.2.0]heptane (4, n = 1) and 7,8-epoxybicyclo[4.2.0]octane (4, n = 2) were prepared by peracid oxidation of the corresponding cyclobutene derivatives. Treatment of the exo-epoxides with a concentrated solution of anhydrous lithium iodide in diethyl ether in... 

The hydrate system formed by lithium iodide will be used to illustrate the stepwise dehydration process. When heated at temperature values below the melting point of anhydrous lithium iodide (446°C), the trihydrate is capable of losing its water of hydration to form a dihydrate and a monohydrate on the way to the anhydrate phase ... 

Conversely, if one begins with the anhydrous lithium iodide and exposes the solid to water vapor, as long as the vapor pressure is less than any of the dissociation pressures, no hydrate phase can form. At the lowest dissociation pressure a univariant system is obtained, since upon formation of the hydrate phase there must be three phases in equilibrium. Since the experiment is being conducted at constant laboratory temperature, the pressure must also be constant. Continued addition of water vapor can only result in an increase in the amount of hydrate phase and a decrease in the amount of anhydrate phase present. When the anhydrate is completely converted, the system again becomes bivariant, and the pressure increases again with the amount of water added. The higher hydrate forms are in turn produced at their characteristic conversion pressures in an equivalent manner. 

After the 5 hours of reflux are over, allow the mixture to cool, then pour it into a sep funnel. Wash the ethyl acetate solution with 50 ml of water to recover the lithium iodide into the water solution. Separate off the water layer, and evaporate the water to recover the lithium iodide for reuse. The ethyl acetate solution should be dried over some anhydrous sodium sulfate, then the ethyl acetate evaporated off to give about 20 grams of 2,4,5-trimethoxyphe-nlyacetone. This light-sensitive substance should be stored in the freezer. 

Anhydrous acetic acid melts at 16.635°C and has a cryoscopic constant, Ac = 3.59 Kkgmol . ° Raoult used this solvent for molecular weight determinations and it has been used by several workers " for the investigation of hydrocarbon solutes. The dielectric constant is 6.194 at 18°C. Few investigations of electrolyte solutions have been reported and association is pronounced. Lithium salts in particular, appear to polymerise in acetic acid solution. Turner and Bissett found that lithium iodide, and to a lesser extent lithium nitrate, appear to polymerise, though sodium iodide did not exhibit similar behaviour. Kenttamaa calculated equilibrium constants for the reaction... 

A dichromium derivative has been prepared from pinacol (dichloromethyl)-boronate (163), anhydrous chromous chloride, and lithium iodide in THF at 25 °C [90]. With various aldehydes, RCHO, this reagent adds to the carbonyl carbon to form trans-l-alkenylboronic esters, RCH=CH-B(02C2Me4). For most examples yields were 84-91%, E Z ratios >95 5. This reaction was used recently to convert aldehyde 162 into alkenylboronic ester 164, an intermediate used for a Suzuki-Miyaura coupling in the asymmetric total synthesis of quinine and quinidine (Scheme 8.39) [91]. In the modified procedure, the chromium reagent was generated from 163 in the presence of the aldehyde substrate. 

Aldol Reactions.—Anhydrous lithium iodide in ether is an effective reagent for the formation of a./S-unsaturated ketones via aldol condensations between ketones and aldehydes [equation (44)].In the presence of trimethylsilyl chloride and triethylamine, the aldol product is trapped as the silyl ether derivative, as a mixture of stereoisomers. 

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