Sodium bromide-methanol solutions

The oxidative reaction of furan with bromine in methanol solution or an electrochemical process using sodium bromide produces 2,5-dimethoxy-2,5-dihydrofuran (19), which is a cycHc acetal of maleic dialdehyde. The double bond in (19) can be easily hydrogenated to produce the corresponding succindialdehyde derivative. Both products find appHcation in photography and as embalming materials, as well as other uses. 

Unsaturation value can be determined by the reaction of the akyl or propenyl end group with mercuric acetate ia a methanolic solution to give acetoxymercuric methoxy compounds and acetic acid (ASTM D4671-87). The amount of acetic acid released ia this equimolar reaction is determined by titration with standard alcohoHc potassium hydroxide. Sodium bromide is normally added to convert the iasoluble mercuric oxide (a titration iaterference) to mercuric bromide. The value is usually expressed as meg KOH/g polyol which can be converted to OH No. units usiag multiplication by 56.1 or to percentage of vinyl usiag multiplication by 2.7. 

Both equations give the weight percent of sodium bromide iu an aqueous saturated solution to within 0.02 percentage units. One gram of sodium bromide dissolves iu about 16 mL of ethanol and 6 mL of methanol (3). 

P 58] Another protocol focused on continuous contacting of the two reactant solutions. Again, flow was fed by electroosmotic means [13]. A 0.01 M methanol solution of 2-nitrobenzyltriphenylphosphonium bromide was used a 0.02 M methanol solution for methyl 4-formylbenzoate with sodium methoxide (0.015 M) was used. Volumes of 80 pi of both solutions were set in the respective reservoirs on the chip and 40 pi of methanol in the collection reservoir. A voltage of 400 V was applied for both feed lines. The reactions were carried out at room temperature and run for 20 min. 

P 59] A third protocol differed from [P 57] and [P 58] by sequential insertion of all reactants instead of using a pre-mixed solution of nitrobenzyltriphenyl-phosphonium bromide and sodium methoxide. As above, flow was fed by electroosmotic means [13]. A 40 pi volume of a methanol solution of 0.01 M 2-nitrobenzyl-triphenylphosphonium bromide was filled into the first reservoir, 40 pi of a methanol solution of 0.015 M sodium methoxide in the second, 40 pi of a methanol solution... 

The electrolyte is a 20% solution of the furan in methanol containing sodium bromide. The bromide ion plays an essential role since bromine and brominated furans are probably important intermediates in the anodic processes [10]. Organic yields as high as 97% with current efficiencies of 80 to 95% are reported for electrolytes run below 10°C. 

The TPA process. The technology involves the oxidation of p-xylene, as shown already in Figure 18—2. The reaction takes place in the liquid phase in an acetic acid solvent at 400°F and 200 psi, with a cobalt acetate/ manganese acetate catalyst and sodium bromide promoter. Excess air is present to ensure the p-xylene is fully oxidized and to minimize by-products. The reaction time is about one hour. Yields are 90—95% based on the amount of p-xylene that ends up as TPA. Solid TPA has only limited solubility in acetic acid, so happily the TPA crystals drop out of solution as they form. They are continuously removed by filtration of a slipstream from the bottom of the reactor. The crude TPA is purified by aqueous methanol extraction that gives 99 % pure flakes. 

The compounds were received from T. G. Traylor s laboratory in the Fe(lII) chloride form. Approximately. 4 mg of this crystal was dissolved in absolute methanol, degassed, and brought back to atmospheric pressure with argon. Aqueous solutions of cetyltrimethylam-monium bromide (CTAB) were prepared, filtered and bubbled with carbon monoxide gas to saturate the system. Sodium dithionite was added for the reduction of Fe(lII) to Fe(ll) and the methanol solution of the heme was added to the CTAB to create an aqueous solution -5 -4... 

The Williamson synthesis, using a sodium phenoxide and allyl bromide in methanol solution, is more rapid than the procedure using acetone and potassium carbonate and gives good results.16-36 441 66 Aqueous acetone also has been used as the reaction medium with allyl bromide and sodium hydroxide this method likewise is rapid and sometimes leads to better yields than the procedure using potassium carbonate and acetone.34 Allylation of 2-hydroxy-l,4-naphthoquinone has been carried out by treating the silver salt, in benzene, with allyl bromide 84 some C-alkylation as well as O-alkylation was observed. 

Dihydro-l//-2-benzotelliirin (Kongalite Method)2 34 g (0.17 mol) of sodium formaldehyde sulfoxylate, 26 g (0.65 mol) of sodium hydroxide, and 100 ml of water are placed in a flask fitted with a stirrer, a reflux condenser, and a nitrogen inlet tube. The flask is flushed with nitrogen, 15 g (0.12 mol) of fine tellurium powder is added, and the mixture is stirred and heated on a water bath for 30 min. 100 ml of ethanol and a solution of 25 g (0.09 mol) of 2-(2 -bromoethyl)benzyl bromide dissolved in 150 mi of hot ethanol are added. The mixture is stirred and heated under reflux for 2 h, the ethanol is distilled off, and the residue is ground, then extracted with a mixture of 300 ml of water and 300 ml of diethyl ether. The diethyl ether layer is separated, washed with water, dried with anhydrous sodium sulfate, filtered, and fractionally distilled yield 8.5 g b.p. 116-12670.3 torr. The residue from the extraction is boiled with 50 m/of ethanol, the mixture is filtered hot, and the filtrate allowed to cool. The crystals are collected (3.8 g) and the combined product fractions are recrystallized from methanol whereby the methanol solution is cooled in dry ice yield 12.3 g (54%) m.p. 64°. 

Bis[4-methylphenyl] Tellurium Bis[2-(4 -methylbenzylidenamino)phenoxide]4 A solution of sodium methoxi-de in 30 ml absolute methanol, prepared by the addition of 0.95 g (40 mmol) sodium to methanol, is added to a stirred solution of 9.40 g (20 mmol) of bis [4-methylphenyl] tellurium dibromide in 50 ml dry toluene. Methanol is distilled from the reaction mixture until the temperature of the vapors reach 110°. Sodium bromide is removed by filtration, The filtrate, containing his[4-methylphenyl] tellurium dimethoxide, is added to a stirred solution of 8.44 g (40 mmol) of 2-(4-methylbenzylidenamino)phenol in 50 ml dry toluene. Most of the toluene is distilled under vacuum from the reaction mixture. The concentrate ( 30 ml) is mixed with an equal volume of absolute diethyl ether. The mixture is cooled to — 5°. The crystals are collected by filtration and recrystallized from hexane m.p. 135°. 

The Williamson synthesis, using a sodium phenoxide and allyl bromide in methanol solution, is more rapid than the procedure using acetone and potassium carbonate and gives good results. - Aqueous ace-... 

Because of the hygroscopic nature of cyclopropyltriphenylphosphonium bromide (13) use of the tetrafluoroborate salt 16 is recommended. This salt may be prepared in 93% yield by dissolution of the bromide salt and excess sodium tetrafluoroborate in aqueous methanol. Extraction of the aqueous methanolic solution with chloroform, and evaporation of the dried chloroform solution, yields pure tetrafluoroborate salt 16. ... 

Kodak) and cetyltrimethylammonium bromide, gTAB (Sigma) were purchased as indicated and then purified by recrystallization from ethanol. However, hexyltrimethylcunmonium bromide (CgTAB) and octyltrimethylammonium bromide (CgTAB) were synthesized by refluxing either 1-bromohexane or 1-bromooctane (Aldrich) with trimethylamine methanol solution and finally recrystallized twice from benzene.(5) An anionic surfactant, sodium dodecyl sulfate,... 

To a solution of dibromomethylbismuthine (3.84 g, 10 mmol) in absolute methanol was added dropwise a solution of sodium methoxide (prepared from sodium 0.46 g, 20 mmol in methanol), and the resulting mixture was warmed gradually to 50°C. The precipitated sodium bromide was filtered off and a methanol solution of an appropriate thiol (20 mmol) was added dropwise to the filtrate at room temperature. The volatiles were removed off in vacuo and the residue was cooled to precipitate a yellow solid, which was filtered and recrystallized from ethanol. The yields of methylbismuth dithiolate from 2-propanethiol, 2-methyl-2-propanethiol, cyclohex-anethiol and 4-methylbenzenethiol were in the range 57-75% [78ZAAC(439)139]. 

To obtain a perchlorate of this series, a methanolic solution of the related bromide salt is mixed with an excess of a concentrated aqueous solution of sodium perchlorate. An orange, crystalline precipitate is collected by filtration, washed with water, and dried by suction. 

Inasmuch as the hexol sulfate is sparingly soluble in water, it is converted into the chloride by metathesis with barium chloride solution and then isolated as the bromide as follows. The sulfate (1.1 g) is added to a solution containing 1.6 g of barium chloride dihydrate in SOmL of cold 0.001 M hydrochloric acid, and the suspension is stirred for about 3 min. The white precipitate of barium sulfate is removed by suction filtration, and 15 mL of cold 0.001 M hydrochloric acid, saturated with sodium bromide, is added to the filtrate. The fine, dark brown crystalline deposit of ( — )-hexol bromide dihydrate is filtered, washed with 10 mL of methanol, and air-dried. The yield is 1.0 g (31.5%, based on the assumption of equal amounts of each antipode in the racemic hexol iodide tetrahydrate). 

The diazoketoester 20 undergoes cyclopropanation to the unstable pentacycle 6 (major product) when added dropwise to a solution of copper(ll)bis-salicylalde-hyde-/-butylimine in toluene, involving the intermediate carbene 7. Sodium boro-hydride reduces 6 in methanol solution to the secondary alcohol which is, for protection, converted to the benzyleflier 21 by Williamson synthesis involving deprotonation to the alcoholate by sodium hydride and 0-alkylation by benzyl-bromide so that diisobutylaluminumhydride (DIBAH) reduces the i-butylester in 21 to the primary alcohol 22 in dichloromethane. 

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