Distillation Dean-Stark

A mixture of tritylamine (13 g, 0.050 mol) and a freshly distilled aldehyde (0.055 mol) in benzene (50 mL) was heated to reflux in a Dean-Stark distillation device with a calibrated receiver. When the calculated amount of H20 (0.9 mL) had separated, the mixture was concentrated to give the product, which was recrystallized. For acetaldehyde imine 1 (R =Trt R2=Me) yield 100% mp 144-147°C (dec). 

Extraction with a solvent (Dean-Stark distillation apparatus) ... 

Water removal can be accomplished by using Dean-Stark distillation, molecular sieves, CaS04, CUSO4, or water scavengers such as Triethyl Orthoformate or dialkyl sulfites... 

Note 1). The mixture is heated with a mantle with stirring for 32 hr under a 50-cm fractionating column packed with 5-nm glass beads and topped by a Dean-Stark trap. The reaction mixture is then distilled through the packed column. The fraction which boils at 120 -126°C is collected. The yield is 86.0-87.3 g (77-78%) of 2,2-dimethyl-4-pentenal (1) as a clear, colorless oil, n 1.4216 (Note 2). 

A. 0-Methyl-ls -2-octalone id,lA-Dimethylhydra2one. A 250-ml., round-bottomed flask equipped with a magnetic stirring bar and a Dean-Stark water separator is maintained under a dry nitrogen atmosphere (Note 1) and eharged with 7.4 g. (0.045 mole) of 10-methyl-A -2-oetalone [2(3 f)-Naphthalenone, 4,4a,5,6,7,8-hexahydro-4a-methyl-] (Note 2), 9.0 g. (0.15 mole) of N,N-dimethylhydrazine, 150 ml. of dry benzene, and 0.02 g. of p-toluenesulfonie aeid. This mixture is refluxed for 10-14 hours, after whieh time no further water separates. Benzene and excess N,A -dimethylhydrazine are then removed by simple distillation, and the residue is distilled under reduced pressure to give 8.1 g. (87%) of the dimethylhydrazone as a pale-yellow liquid, b.p. 94-98 (0.2 mm.) (Notes 3, 4). 

In a 1-L rbf attached to a Dean-Stark trap, equipped with a reflux condenser is placed distilled aniline (1, 46.5 g, 45.5 mL, 0.5 mol), commercially available ethyl acetoacetate (5, 65 g, 63.5 mL, 0.5 mol), benzene (100 mL) and glacial AcOH (1 mL). The flask is heated at about 125 °C, and the water which distills out of the mixture with the refluxing benzene is removed at intervals. Refluxing is continued until no more water separates (9 mL collects in about 3 hrs) and then for an additional 30 min. The benzene is then distilled under reduced pressure, and the residue is transferred to a 125 mL modified Claisen flask with an insulated column. The flask is heated in an oil or metal bath maintained at a temperature not higher than 120 °C while the forerun of 1 and 5 is removed and at 140-160 °C the product distills giving 78-82 g, 76-80% yield of 6. 

Azeotropic drying of organic substances is also effective, providing the material is relatively nonvolatile. A benzene or toluene solution of the compound is distilled (in a Dean-Stark trap, if available) until the distillate is free of water droplets. The remaining solution is essentially dry. 

Soya oil, 88.6 g, 20.0 g of pentaerythritol, and 0.06 g of lithium hydroxide monohydrate are weighed into a 250-mL three-necked round-bottom flask fitted with a magnetic stirrer, a Dean-Stark separator, and nitrogen inlet and outlet. The reaction mixture is heated to 250°C for 30 min under nitrogen (note a below), then cooled to 200°C. Phthalic anhydride, 34.6 g, 0.70 g of maleic anhydride, and 8.0 g of xylene are added. The reaction mixture is heated to 230°C and the toluene-water azeotrope is removed by distillation. The reaction is stopped when the acid number of reaction medium is lower than 10 (note b below). After cooling to room temperature, 52 g of white spirit is added. 

Toluene (99.8% anhydrous, water <0.001%, evaporation residue <0.005%) was purchased from Aldrich Chemical Company and used as received. The capacity of the receiver in the Dean-Stark trap was 28 mL. The initial amount of toluene placed in the flask was 88 mL. Upon heating to reflux, 28 mL of toluene was distilled from the flask and collected in the receiver. The remaining volume of toluene in the reaction flask was ca. 60 mL, corresponding to an approximately 0.50M concentration of the reactants. 

Bromomethyl acetyl sulfide (26.8 g, 0.16 mol) and triethyl phosphite (28.4 g, 0.17 mol) were combined in a flask fitted with a Dean-Stark trap. The mixture was stirred at 130°C for 2.5 h, during which time ethyl bromide collected in the Dean-Stark trap. The reaction mixture was vacuum distilled to give the pure (diethyl phosphonomethyl) acetyl sulfide (23.5 g, 65%) as a clear oil of bp 105 to 106°C/0.03 torr, which exhibited NMR spectra in accord with the proposed structure. 

Mix 0.25M substituted benzaldehyde, 0.3M nitroethane, 50 ml dry toluene and 5 ml n-butylamine (or other amine), and reflux 3 hours with a Dean-Stark trap (or prepare the nitro-propene as described elsewhere here). Add 50 g iron powder and 1 g FeCl3 optional) and reflux while adding 90 ml concentrated HCI over 3 hours. Reflux 1 hour more, add 2 liters of water and extract 3 times with ether, then dry and evaporate in vacuum (or steam distill until about 3.5 liters of distillate is obtained extract the distillate 3 times with toluene wash the toluene layers with 7 g NaHS03 in 225 ml of water, then 3 times with water and dry, evaporate in vacuum) to get the ketone. Mix 0.13M ketone, 28 g formamide (or dimethyl-formamide if the N.N-dimethylamine is desired) and 3 ml formic acid and heat at 160°. Add 3 more ml formic acid and heat 16 hours at 170-180° adding formic acid from time to time to keep the pH acid. Distill off the water formed (about 16 ml), cool and extract with 3X70 ml benzene. Distill off the benzene and reflux the residue 7 hours with 30 ml concentrated HCI. Chill, basify with 10% NaOH and extract with 3X70 ml ether. Dry and evaporate the ether in... 

A. 1-Pyrrolidinocyrtohexene.2 3 A solution of 29.4 g. (0.3 mole) of cyclohexanone and 28.4 g. (0.4 mole) of pyrrolidine in 150 ml. of benzene is placed in a 500-ml., one-necked flask to which a Dean-Stark water separator is attached. The solution is refluxed under a nitrogen atmosphere until the separation of water ceases (Note 1). The excess pyrrolidine and benzene are removed from the reaction mixture on a rotary evaporator. The resulting residue is stored under refrigeration and distilled just before use in the next step to provide 44.6 g. of 1-pyrrolidinocyclohexene, b.p. 76-77° (0.5 mm.), 105-106° (13 mm.). 

Lithiimi iodide dihydrate is available from Fluka A.G., Buchs, S.G., Switzerland. The checkers used the trihydrate and, by means of a Dean Stark trap attached between the flask and the condenser, 1 mole, of water was removed via azeotropic distillation with collidine. 

A mixture of the above diol, PHBA, p-TSA and "Aromatic 150" was heated under N2 in a 3-neck flask equipped with stirrer, Dean-Stark trap, condenser and thermometer. The PHBA/diol wt. ratio varied from 20/80 to 60/A0 0.2 wt. % of p-TSA was used. About 10 wt. % of "Aromatic 150" was used the amount was adjusted to maintain the temperature at 230 +/- 3°. Distillate (cloudy H2O) was collected in the Dean-Stark trap during 9 to 11 hr. The reaction mass was cooled to 115°, and MIBK was added to yield a solution (20/80 PHBA/ diol ratio) or dispersion (other PHBA/diol ratios) of the crude polyol. 

C. l-d-2-Methylbutanal. A 1-1. three-necked round-bottomed flask is equipped with a dropping funnel, a gas inlet tube for steam, and a Dean-Stark trap to which is attached a condenser through which acetone cooled to —15° is circulated (Note 15). A solution of 50.4 g. (0.40 mole) of oxalic acid dihydrate in 200 ml. of water is added to the flask, and the solution is heated at reflux. Steam is introduced into the flask, and when some begins to condense,in the Dean-Stark trap, the distilled aldimine from part B is added dropwise from the funnel. The aldehyde and water collect in the trap, and the water layer is periodically removed. After the distillation of the aldehyde is complete, the product is drained from the trap, and the water layer is separated... 

The reaction from an enamine is initiated by the addition of a trace of a strong acid, e.g. /7-toluenesulfonic acid (TsOH, 4-methylbenzene-sulfonic acid), to the ketone and pyrrolidine in a solvent such as toluene. When the mixture is at reflux in a Dean-Stark apparatus, water is liberated and is removed through azeotropic distillation, leaving the enamine in the reaction vessel. After a follow-up reaction between the enamine and a suitable electrophile, an iminium salt is produced that liberates both the a-substituted ketone and pyrrolidine when it is treated with aqueous acid (Scheme 6.20). 

In a system containing a Dean Stark trap arranged for azeotropic removal of water. 9.3 g (56 mmol) of (-)-(S)-a-(mcthoxymethyl)benzeneethanamine and 6.5 g (66 mmol) of cyclohexanone arc dissolved in 100 mL of benzene or toluene and heated to reflux until the theoretical amount of water is collected in the trap. Removal of the solvent and distillation of the oily residue gives a clear viscous oil yield 13.0 g (93 %) bp (Kugelrohr) 95-100°C/0.5 Torr [a]D —46.2 (c = 6.7, methanol). 

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