Recrystallization water trap

B. a-Hydroxyphenazine (demethylalion). A solution of 4.2 g. (0.02 mole) of a-methoxyphenazine, from A above, in 125 ml. of 55% hydrobromic acid (Note 7) is placed in a 250-ml. round-bottomed flask fitted with a reflux condenser. The flask is immersed in an oil bath, and the solution is heated to 110-120° for 5 hours the evolved gases are absorbed with water in a trap. The reaction mixture is cooled to room temperature, diluted with about 125 ml. of water, almost neutralized with sodium hydro.xide (Note 8), and extracted six times with 30- to 40-ml. portions of ether. The combined ether extracts arc extracted with 25-ml. portions of 10% sodium hydroxide solution (Note 9) until no more purple sodium salt is remox ed from the ether. The aqueous extracts are combined, made acid to litmus with dilute acetic acid, and re-extracted four times with 50-ml. portions of ether. The combined ether extracts are dried over anhydrous sodium sulfate, and the ether is removed by distillation on a steam bath. The residue is recrystallized as follows It is dissolved in the least possible amount of hot alcohol, water... 

A mixture of 17.6 grams of p-n-butoxyacetophenone, 12.1 grams of piperidine hydrochloride, 4.5 grams paraformaldehyde, 0.25 cc concentrated hydrochloric acid, 52.5 cc nitro-ethane, 7.5 cc of 95% ethanol, and 15 cc of toluene was boiled under reflux for one hour, removing water formed in the reaction by means of a condensate trap. The mixture was then cooled. The crystals which formed were collected by filtration, washed with anhydrous ether and recrystallized from methyl ethyl ketone. The crystals thus obtained, which melted at 174°-175°C, were shown by analysis to be 4-n-butoxy-beta-piperidinopropiophen-one hydrochloride. 

Azobis-(2-methylpropionitrile) (ABN) was recrystallized from methanol. Azobis-l-cyanocyclohexane (ABC) was furnished by D. E. Van Sickle, and di-ferf-butylperoxalate (DBPO) was prepared by a literature procedure (2). Oxygen (99.9% ) was passed through a — 80°C. trap to remove trace amounts of water. 

The benzylideneanilines of Table IX are prepared by refluxing a mixture of 0.010 mole each of the appropriate para-substituted benzaldehyde and aniline in 150 ml of benzene containing 0.1 gm of benzenesulfonic acid for 2-4 hr. A Dean-Stark trap is used to collect the water and then the solvent is removed under reduced pressure. The residue is recrystallized from hexane or other... 

Bis[4-methoxyphenyl] Ditellurium1 Sodium borohydride (81 mg, 2.2 mmol) in 3 ml ethanol is added to 670 mg (2.0 mmol) of 4-methoxyphenyl phenylethynyl tellurium in 10 ml ethanol at 40°. The solution is stirred for 10 min then 0.5 ml water and 0.5 ml of 10% aqueous sodium hydroxide are added. The mixture is cooled to 0J and stirred for 10 min. The mixture is then diluted with 30 ml diethyl ether, then washed with brine, and the organic layer separated, dried with anhydrous magnesium sulfate, filtered, and the solvent evaporated from the filtrate. Phenylacctylene iscautiously evaporated at reduced pressure and collected in a trap cooled to — 78°. The residue is recrystallized from diethyl ether yield 95% m.p. 58°. 

Diaryl Tellurium 3-Mercaptopropanoate3 To a solution of 0.05 mol of the diaryl tellurium oxide in 50 ml anhydrous toluene are added 0.05 mol 3-mercaptopropanoic acid. The stirred mixture is refluxed for 3 h. Water is removed by azeotropic distillation and collected in a Dean-Stark trap. The toluene is evaporated. The diphenyl derivative is purified by preparative thin-layer chromatography and column chromatography with toluene as mobile phase. The ethoxyphcnyl derivative is recrystallized from benzene and hexane. Compounds thus prepared include ... 

Without further drying, the potassium 4-chloro-3,5-dinitro-benzenesulfonate is recrystallized from 600 ml. of boiling water (Note 3). Insoluble material is removed by decantation and filtration of the hot solution. The solution is cooled to 5-10° for 12 hours, and the crystalline potassium salt is collected on a suction filter, pressed as dry as possible, and placed at once in a solution of 400 ml. of concentrated ammonium hydroxide (sp. gr. 0.90) in 400 ml. of water. The solution is boiled for 1 hour under a reflux condenser which has been connected to a gas absorption trap,2 and then is cooled at 5-10° for 12 hours. The orange, crystalline potassium 4-amino-3,5-dinitrobenzenesulfo-nate is filtered with suction and pressed as dry as possible on a 10-cm. Buchner funnel. 

A mixture of concentrated hydrochloric acid (175 ml) and water (175 ml) is added to the acetamidoacetone (52 g, 0.45 mol). The mixture is boiled under reflux in a nitrogen atmosphere (6h) and concentrated by flash evaporation below 60°C using a condensation trap for solvent cooled in a dry-ice-acetonc bath. A dark, oily residue (40-45 g) is obtained. This is very hygroscopic but can be dried over P2O5 in a vacuum desiccator. Purification is achieved by recrystallization from absolute ethanol, adding ether until cloudy. This reagent can be stored as the semicarbazone, from which aminoacetone can be generated as required in siru. 

After recrystallization it is usually necessary to dry the material. This may be done by spreading the material out on a large piece of filter paper and permitting the solvent to evaporate. Otherwise the material may be placed in a vacuum desiccator which is then evacuated by a mechanical pump protected by a dry ice-acetone cooled trap. If the solvent was water, an alcohol, or a compound easily absorbed by... 

Schiff base condensation reactions have also been widely used in the preparation of new imine-functionalized tertiary phosphines (64) (68).122-129 The most frequently used experimental procedure involves the condensation of a carbonyl compound (often 2-Ph2PCeH4CHO)176 and the appropriate amine in ethanol, benzene, or THF under refluxing conditions. To ensure complete reaction, a Dean-Stark trap or the addition of molecular sieves is often necessary, to remove water formed during the reaction. Evaporation of the solvent and recrystallization yield the desired ligand in good to excellent yields. This approach can be used to prepare bis-phosphines, e.g., (66)-(68).127- 29 The iminophosphine (69) was prepared by a series of coupling reactions at a palladium template, and was liberated from the metal by treatment with aqueous cyanide.130... 

Under stirring, a-bromo(dineopentyl) ketone (33.6 g, 0.135 mol), cooled by an ice-water bath, was triturated over a period of 30min with a solution of t-BuOK in /-BuOH (120 mL, l.OM, 0.12mol) (prepared by addition of potassium metal to freshly distilled, sodium-dried t-BuOH and standardized by back titration of an aliquot with 0.1 N aq HCl). When the mixture solidified, the iee-bath was removed. The mixture was concentrated at ca. 60 °C (25 Torr) and trap-to-trap distilled at 25 -100 "C (0.1 Torr). Recrystallization of the distillate from pentane at — 78 "C gave /ranr-2,3-di-/er/-butylcyclopropanone yield 16.8 g (75%) bp 75-77°C/20Torr mp 24-26 C the yield can vary from 30 to 75%. 

To a suspension of the alkylmagnesium bromide (50 mmol, 25 % excess) in THF (200 mL, cooled to — 78 °C) was added Ti(0-i-Pr)4 (20 mmol) in THF (10 mL) under Nj through a steel cannula. After the mixture had been stirred for 2 min, the dialkylamide (20 mmol) in THF (10 mL) was added, and the mixture allowed to warm to 20 °C. After stirring for an additional 3 h volatile amines (with boiling points elose to that of THF and i-PrOH) together with THF were distilled from the reaction mixture, without adding water, under reduced pressure (lOOTorr) into a cold trap (— 78" C). Addition of a solution of HCl in EtjO precipitated the hydrochloride of the cyclopropylamine. The crystals were collected and recrystallized (CHCh/EtjO). 

Extremely wet solids (solid floating in water). Set up a gravity filtration (see Chapter 13, Recrystallization ) and filter the liquid off of the solid. Remove the filter paper cone with your solid product, open it up, and leave it to dry. Or remove the solid and dry it on fresh filter paper as above. Use lots of care, though. You don t want filter paper fibers trapped in your solid. 

Dihydroxybenzoic acid (18.8 g, 120 mmol), butanol (23 mL, 250 mmol), and H2SO4 (3-4 mL, cone.) are refluxed in toluene previously dried over sodium (25 mL) in a flask equipped with a Teflon-coated magnetic stirrer and a Dean-Stark trap for 9 h. On completion of the reaction (as revealed by TLC), the product is poured into water and extracted with ether. Washing with sodium hydrogen carbonate solution and then water followed by recrystallizing from petroleum ether (60-80 fractions) gives the product as a white solid. 

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