Lithium chloride-methanol solutions

The thermal decomposition of some 3,5-disubstituted-l,2,4-thiadiazoles has been studied and some nonisothermal kinetic parameters have been reported <1986MI239>. Polarographic measurements of a series of methylated 5-amino-l,2,4-thiadiazoles show that thiadiazoles are not reducible in methanolic lithium chloride solution, while thiadiazolines are uniformily reduced at 0.5 = — 1.6 0.02 V. This technique has been used to assign structures to compounds which may exist theoretically as either thiadiazoles or thiadiazolines <1984CHEC(6)463>. The photoelectron spectrum for 1,2,4-thiadiazole has been published <1996CHEC-II(4)307>. 

Suggestive evidence for the protonation of diphenylcarbene was uncovered in 1963.10 Photolysis of diphenyldiazomethane in a methanolic solution of lithium azide produced benzhydryl methyl ether and benzhydryl azide in virtually the same ratio as that obtained by solvolysis of benzhydryl chloride. These results pointed to the diphenylcarbenium ion as an intermediate in the reaction of diphenylcarbene with methanol (Scheme 3). However, many researchers preferred to explain the O-H insertion reactions of diarylcarbenes in terms of electrophilic attack at oxygen (ylide mechanism),11 until the intervention of car-bocations was demonstrated by time-resolved spectroscopy (see Section III).12... 

Cabon tetrachloride, n-hexane, chloroform, ACN, acetone, THF, pyridine, acetic acid, and their various mixtures were applied as mobile phases for adsorption TLC. Methanol, 1-propanol, ACN, acetone, THF, pyridine and dioxane served as organic modifiers for RP-TLC. Distilled water, buffers at various pH (solutions of and dipotassium hydrogen phosphate or potassium dihydrogen phosphate) and solutions of lithium chloride formed the aqueous phase. Carotenoids were extracted from a commercial paprika sample by acetone (lg paprika shaken with 3 ml of acetone for 30 min), the solution was spotted onto the plates. Development was carried out in a sandwich chamber in the dark and at ambient temperature. After development (15 cm for normal and 7cm for HPTLC plates) the plates were evaluated by a TLC scanner. The best separations were realized on impregnated diatomaceous earth stationary phases using water-acetone and water-THF-acetone mixtures as mobile phases. Some densitograms are shown in Fig.2.1. Calculations indicated that the selectivity of acetone and THF as organic modifiers in RP-TLC is different [14],... 

Another important factor in electroreduction is the electrolyte. Most electrolytic reductions are carried out in more or less dilute sulfuric acid but some are done in alkaline electrolytes such alkali hydroxides, alkoxides or solutions of salts like tetramethylammonium chloride in methanol [128] or lithium chloride in alkyl amines [729,130]. 

A solution of lithium chloride (68 mg, 1.6 mmol) in 2mL of methanol is prepared and added to the orange solution described earlier. A white product gradually precipitates and is filtered away after 30 min. 

Section A) (0.30 g, 0.45 mmol) and 20 mL of acetone. To this suspension, an aqueous solution (10 mL) of lithium chloride (0.076 g, 1.8 mmol) is added. The reaction mixture is stirred for 2 days at room temperature. The resulting pale yellow solid is filtered through a medium-porosity fritted glass and washed with aqueous methanol (50%, 20 mL). Yield 0.25 g (90%). 

Experiments using a series of methylated 2-amino-1,2,4-thiadia-zoles of unequivocal structure (351-353) show that thiadiazoles (e.g. 351) are not reducible in methanolic lithium chloride solution, while thiadiazolines (e.g. 352-353) are uniformly reduced at E0 = — 1.6 + 0.02V. In aqueous alcoholic tetramethylammonium iodide,... 

The second piece of evidence against the mechanism of Figure 10-7 is that bromine addition reactions carried out in the presence of more than one nucleophilic reagent usually give mixtures of products. Thus the addition of bromine to an alkene in methanol solution containing lithium chloride leads not only to the expected dibromoalkane, but also to products resulting from attack by chloride ions and by the solvent ... 

Cobalt(II) Chloride and Methanol. Passage of chlorine into a solution of cobalt chloride, bipyridyl, and lithium chloride in methanol resulted in an explosion and ignition of the methanol, probably due to formation of methyl hypochlorite.8 9... 

Phenotellurazine 26.5 g (0.16 mol) of diphenylamine, 50 g (0.16 mol) of mercury(ll) acetate, and 500 ml of methanol are placed in a 1-/ round-bottom flask fitted with a magnetic stirrer and a reflux condenser. The mixture is stirred and heated under gentle reflux for 12 h, cooled to 20c, and a solution of 14.0 g of lithium chloride in 50 ml of methanol is added. The resultant mixture is stirred at 20° for 12 h, and the colourless solid is filtered and dried in a dessicator yield of dry 2-chloromercuriodiphenylamine 56 g (80%). 

The alkali elution curves of the displacement chromatography are shown in Fig. 17, the ratio Li/ Li dependent on the effluent volume is given in Fig. 18. As one can see from Fig. 18, an increase of the Li/ Li ratio from 0.07 to 0.09 is found within the lithium elution band which corresponds to a column length of 91 cm. The relative enrichment of the heavy lithium isotope Li in the first fractions — that is in the methanolic phase — agrees with isotopic separations of calcium using a condensation resin with dibenzo(18]crown-6 and [2b.2.2], respectively (Chap. 4.3.2.3 and Chap. 4.3.2.4). Fujine and coworkers have also carried out one breakthrough experiment with methanolic solutions of cesium chloride and lithium acetate The evaluation of the front analysis with Spedding and coworkers method resulted in an isotopic separation factor of a = 1.014. 

Table IV also includes some values determined in methanol as the solvent these are very much higher (and, hence, also more accurate) than those in water, because the polyol competes with methanol, rather than with water, for outer-sphere positions on the cation. These figures explain why carbohydrates are soluble in methanol or ethanol containing high concentrations of calcium chloride, or even potassium acetate, and in such systems as lithium chloride in 2-methoxyethanol. ° Sugar derivatives that are soluble in non-hydroxylic solvents form complexes with cations in those solvents even more readily for example, methyl 2,3-0-isopropylidene-4-0-methyl-) -L-rhamnopyranoside (24) (but not its a anomer) will form a complex with sodium iodide in acetone, the Na" " ion coordinating to 0-1,0-2, and 0-3. In aqueous solution, the concentration of this complex would be negligible.

The treatment of small ferrous artefacts in a 0.05 M lithium hydroxide dissolved in methanol or ethanol has its advocates, particularly in France. The chlorides present in the rust layers react with lithium hydroxide to form lithium chloride that dissolves in the alcohol phase. Any of the hydroxide left on the metal surface combines with any carbon dioxide to form a solution with pH above 9.5, which maintains any exposed metal in the passive region. Hence, this solution is claimed to cause no corrosion of the underlying metal. The real disadvantage of this solution is that any lithium chloride left on the surface of the artefact is very hygroscopic. Water will form on the surface at a relative humidity above 15% RH and corrosion of the metal will take place. Humidity levels below 15% RH are very difficult to maintain in display cabinets or in storage and is one of the main reasons why this solution has not been more widely employed. 

Budyina and Marinin [130] have described methods based on anodic voltammetry for the determination of lonol (2,6-di- -butyl-p-cresol) and quinol in polyester acrylates. To determine lonol the sample is dissolved in 25 ml of acetone and a portion (10 ml) is treated with 2.5 ml of acetone and 5 ml of methanol and diluted to 25 ml with a solution 0.1 M in lithium chloride and 0.02 M in sodium tetraborate. A polarogram is recorded with a graphite-rod indicator electrode. To determine quinol, the sample (1 to 3 g) is dissolved in 80 ml of methanol or methanohacetone (1 1) and the solution is diluted to 100 ml with the lithium chloride - sodium tetraborate solution. A polarogram is recorded under the same conditions. Concentrations are determined by the addition method. The values versus the SCE) are 0.25 V for lonol and 0.16 V for quinol. 

Addition methods were used for the determination of m-saturated compounds and olefins. The methods are based on the additions of bromine to unsaturated bonds, and the waves for the brominated compounds corresponding to the reduction of o, j8-dibromides (involving elimination) are measured. Their heights are proportional to the concentration of the unsaturated compound. Thus vinylchloride and 1,2-dichloroethylene were transformed into l-chloro-l,2-dibromoethane and l,2-dichloro-l,2-dibromoethane, by the action of a 3 M solution of bromine in methanol saturated with sodium bromide. The excess of bromine was removed with ammonia and the polarographic analysis was performed with sodium sulphite or lithium chloride as a supporting electrolyte. On the other hand, acetylene, vinyl-chloride, 1,2-dichloroethylene and 1,1,2-trichloroethylene were determined ) after a 24 hr reaction with bromine in glacial acetic acid (1 1). The excess bromine was removed with a stream of nitrogen or carbon dioxide. An aliquot portion is diluted (1 10) with a 3 M solution of sodium acetate in 80 per cent acetic acid and after deaeration the curve is recorded. 

Fat oxidation. Peroxides formed in fats can be followed by dissolving 0-01-0-40 g of the oil (so as to give complete solution) in 100 ml. of 0-3 m lithium chloride in a methanol-benzene 1 1 mixture. 

Nitrate the third portion (5 ml.) of the methanolic solution with 4-5 ml. of the nitration mixture (5 parts of concentrated svdphuric acid, 4 parts of concentrated nitric acid). Slowly dilute the mixture, while cooling in ice, with 25 ml. of distilled water. Extract the nitro-products with ether, separate the ether phase and wash with a 5 per cent solution of potassium hydroxide and three times with water. Distil off the ether, dissolve the residue in methanol and polarograph in 0-1 n lithium chloride containing 50 per cent methanol. 

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