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Drying of THF

Playing a dual role, this solvent also acts as a proton source. Since the supply of this proton source—unlike water with the drying of THF (Figure 17.52)—is unlimited in this case, all of the ketone is converted into alkoxide. [Pg.787]

Dissolving metals initially convert aldehydes, ketones, and esters into radical anions. Subsequently, proton donors may react with the latter, which leads to neutral radicals. This mode of reaction is used, for example, in the drying of THF or ether with potassium in the presence of the indicator benzophenone. Potassium and benzophenone react to give the deep-blue potassium ketyl radical anion A (Figure 14.45). Water then protonates ketyl A to the hydroxylated radical B as long as traces of water remain. Further potassium reduces B via another electron transfer to the hydroxysubstituted organopotassium compound C. C immediately tautomerizes to the potassium alkox-ide D. Once all the water has been consumed, no newly formed ketyl A can be pro-tonated so that its blue color indicates that drying is complete. [Pg.583]

In the drying of THF or ether (Figure 14.45), the sequence ketone —> ketyl —> hydroxylated radical —> hydroxylated organometallic compound —> alkoxide is of course not intended to convert all the ketone into product. The reaction depicted in Figure 14.46 features the same sequence of steps as Figure 14.45 (and there is thus no need to discuss their mechanism again). In the reaction of Figure 14.46, however, the reaction is intended to run to completion until all of the ketone has been consumed. The reason for this is that it is the purpose of this reaction to reduce the ketone to the alcohol. The... [Pg.583]

Fig. 14.45. Chemistry of the drying of THF or ether with potassium and benzophenone featuring the ketone -> ketyl reduction and the trapping reaction of the ketyl with residual water. Fig. 14.45. Chemistry of the drying of THF or ether with potassium and benzophenone featuring the ketone -> ketyl reduction and the trapping reaction of the ketyl with residual water.
Synthesis of Alkviamines. General Procedures. Method (A). The synthesis of p-phenethylamine is representative. A flame dried, nitrogen-flushed, 100 ml flask, equipped with a septum inlet, magnetic stirring bar and reflux condenser ivas cooled to 0°C. Sodium borohydride (9.5 mmol, 0.36 g) was placed in the flask followed by sequential addition of THF (13-15 ml) and BF3-Et20 (12 mmol, 1.5 ml) at 0°C. After the addition, the ice bath was removed and the contents were stirred at room temperature for 15 min. The solution... [Pg.139]

A dry reflux set-up is used with a three neck flask allowing a thermometer and sep funnel to be attached to the reaction flask. The thermometer is placed well below the surface of the flask contents. If the temperature rises above 55°C ice will need to be used to cool things down a bit So the three neck flask will be sitting in an ice bath on the stir plate before we begin. If ether is used instead of THF the ether will boil well before 50°C is reached giving a better indication of how hot things are getting. [Pg.235]

To a solution of 0,35 mol of allenyll ithium in about 240 ml of hexane and 200 ml of THF, prepared according to Chapter II, Exp. 13, were added 35 g of dry HMPT at -85°C. r.-Hexyl bromide (0.30 mol) was then added dropwise in 15 min, whilst keeping the temperature of the reaction mixture close to -70 0 (liquid nitrogen bath). After the addition the mixture was held at -60°C for an additional 1 h. [Pg.28]

A solution of 0.35 mol of al1enyl1ithium in about 240 ml of hexane and 240 ml of THF was prepared as described in Chapter II, Exp. 13. To the obtained solution (partly a suspension) were added 40 ml of dry HHPT at -80°C with vigorous stirring. Subsequently the crude bromoether was added over a period of 20 min, while keeping the temperature between -80 and -60°C by cooling in a bath of liquid nitrogen. [Pg.31]

In the flask was placed a solution of 50 g of carbon dioxide in 250 ml of dry THF, made by introducing the gas from a cylinder into THF, cooled at about -90°C (liquid nitrogen bath). The gas inlet was removed and through the neck of the reaction flask was poured a cold solution (-70°C) of 0.40 mol of allenyl1ithiurn in 280 ml of hexane and 280 ml of THF (prepared as described in Chapter II,... [Pg.32]

A solution of 0.10 mol of lithiated methoxyallene in about 70 ml of hexane and 50 ml of THF (see Chapter II, Exp. 15) was cooled to -40°C. Ory, pure acetone (0.12 mol) was added dropwise during 10 min, while keeping the temperature at about -30°. Five minutes after the addition 100 ml of saturated NHi,Cl solution, to which 5 ml of aqueous ammonia had been added (note 1), were run in with vigorous stirring. The product was extracted three times with diethyl ether. The combined organic solutions were dried over potassium carbonate and subsequently... [Pg.43]

The drying agent was filtered off on a sintered-glass funnel and rinsed with some THF. The solution was transferred into a 500-ml wide-necked flask and concentrated in a water-pump vacuum. In order to remove the last traces of THF and some water the flask was connected directly (without a column) to a condenser and a receiver, cooled at -190°. The flask was evacuated by means of a mercury pump (p < 0.1 mmHg) and heated for 1.5 h at 85°C. The greater part of the mono-... [Pg.50]

HCl and 50 ml of water. The upper layer was separated off and the aqueous phase was extracted five times with small portions of THF. After drying the combined solutions over magnesium sulfate the solvent was removed in a water-pump vacuum. The residue was distilled through a 30-cm Vigreux column, connected to an air condenser. After a preliminary aqueous fraction of the carboxylic acid the main fraction passed over at 100°C/15 mmHg. The compound solidified in the receiver and (partly) in the condenser. The yield was almost quantitative. [Pg.59]

To a solution of ethylnagnesium bromide in 350 ml of THF, prepared from 0.5 mol of ethyl bromide (see Chapter 11, Exp. 6) was added in 10 min at 10°C 0.47 mol of 1-hexyne (Exp. 62) and at 0°C 0.47 mol of trimethylsilylacetylene (Exp. 31) or a solution of 0.60 mol of propyne in 70 ml of THF (cooled below -20°C). With trimethyl si lylacetylene an exothermic reaction started almost immediately, so that efficient cooling in a bath of dry-ice and acetone was necessary in order to keep the temperature between 10 and 15°C. When the exothermic reaction had subsided, the mixture was warmed to 20°C and was kept at that temperature for 1 h. With 1-hexyne the cooling bath was removed directly after the addition and the temperature was allowed to rise to 40-45°C and was maintained at that level for 1 h. [Pg.71]

A solution of 0.21 mol of butyllithium in about 140 ml of hexane (note 1) was cooled below -40°C and 90 ml of dry THF ivere run in. Subsequently a cold (< -20 C) solution of 0.25 nol of propyne in 20 ml of dry THF was added with cooling below -20°C and a white precipitate was formed. A solution of 0.10 mol of anhydrous (note 2) lithium bromide in 30 ml of THF was added, followed by 0.20 mol of freshly distilled cyclopentanone or cyclohexanone, all at -30°C. The precipitate had disappeared almost completely after 20 min. The cooling bath was then removed and when the temperature had reached 0°C, the mixture was hydrolyzed by addition of 100 ml of a solution of 20 g of NHi,Cl in water. After shaking and separation of the layers four extractions with diethyl ether were carried out. The extracts were dried over magnesium sulfate and the solvents removed by evaporation in a water--pump vacuum. Careful distillation of the remaining liquids afforded the following... [Pg.75]

After the air in the flask had been completely replaced with nitrogen, it was cooled in a liquid nitrogen bath and a solution of 25 g of acetylene in 160 ml of dry THF was introduced. The solution had been prepared by dissolving acetylene (freed from acetone by means of a cold trap) in THF cooled at -80 to -90°C. A solution of 0.21 mol of butyl lithium in about 150 ml of hexane was added in 5 min to the vigorously stirred solution. During this addition the temperature of the mixture was kept between -80 and -100°C by occasionally dipping the flask into the liquid nitrogen. To the white suspension were successively added at -80°C a solution of 10 g. of anhydrous lithium bromide (note 1) in 30 ml of THF and 0.20 mol of freshly distilled benzaldehyde. The reaction mixture was kept for 3 h at -69°C, after which the temperature was allowed to rise to +10°C over a period of 2 h. [Pg.80]

TO a solution of 0.10 mol of phenyl acetyl one (commercially available, see also Ref. 1) in 100 ml of dry THF was added a solution of 0.21 mol of butyllithium in about 145 ml of hexane. During this addition the temperature was kept below -20°C. The obtained solution was cooled to -65°C and a solution of 0.12 mol of KO-tert.--CijHg (commercially available, see Chapter IV, Exp. 4, note 2) in 100 ml of THF was added, while keeping the temperature below -55°C. After an additional 15 min the cooling bath was removed, the temperature was allowed to rise to -10°C and was kept at that level for 1 h (note 1). The reddish suspension was subsequently cooled to -50°C and 0.32 mol of trimethylchlorosi1ane was added in 10 min. The cooling bath was then removed and the temperature was allowed to rise to 10°C. [Pg.86]

To a mixture of 100 ml of THF and 0.10 mol of the epoxide (note 1) was added 0.5 g Of copper(I) bromide. A solution of phenylmagnesium bromide (prepared from 0.18 mol of bromobenzene, see Chapter II, Exp. 5) in 130 ml of THF was added drop-wise in 20 min at 20-30°C. After an additional 30 min the black reaction mixture was hydrolysed with a solution of 2 g of NaCN or KCN and 20 g of ammonium chloride in 150 ml of water. The aqueous layer was extracted three times with diethyl ether. The combined organic solutions were washed with water and dried over magnesium sulfate. The residue obtained after concentration of the solution in a water-pump vacuum was distilled through a short column, giving the allenic alcohol, b.p. 100°C/0.2 mmHg, n. 1.5705, in 75% yield. [Pg.172]


See other pages where Drying of THF is mentioned: [Pg.786]    [Pg.786]    [Pg.786]    [Pg.228]    [Pg.786]    [Pg.786]    [Pg.786]    [Pg.228]    [Pg.141]    [Pg.2]    [Pg.15]    [Pg.33]    [Pg.34]    [Pg.41]    [Pg.49]    [Pg.50]    [Pg.52]    [Pg.56]    [Pg.59]    [Pg.70]    [Pg.73]    [Pg.84]    [Pg.106]    [Pg.158]    [Pg.160]    [Pg.164]    [Pg.165]    [Pg.168]    [Pg.169]    [Pg.171]    [Pg.173]    [Pg.195]    [Pg.231]    [Pg.233]    [Pg.238]    [Pg.129]   
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