Dean-Stark distillation apparatus

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

Figure 5.1 Dean and Stark distillation apparatus with trap for use with heavy entraining...

Figure 8.2 Different apparatus used for steu distillation. A aodified Gaman steam distillation apparatus A, steam generation flask B, sample chamber C, splash head D, condenser B, delivery tube F, separatory funnel. B = micro steam distillation apparatus A, boiling flask B, collection bulb C, water return arm D, Condenser. C - steam distillation apparatus using a Dean and Stark type trap. D = Nielsen-Kryger steam distillation apparatus.

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). 

Sodium 4-hydroxybenzenesulfonate dihydrate (2.37 g, 0.01 mol) was dehydrated by distillation with benzene using Dean-Stark apparatus and then dissolved in 20 mL of acetone in a lOOmL round-bottomed flask with a reflux condenser. Ethyl bromoacetate (2.04 g, 0.012 mol), potassium carbonate (2.79 g, 0.02 mol) and dibenzo-18-crown-6 (74 mg, 0.2 mmol) were added, and the mixture was heated at reflux for 48 h. After cooling to room temperature, the crystals were collected on a Buchner funnel, washed with acetone (2 x 60 mL), and dried under reduced pressure to yield 2 as a white powder (2.68 g, 95 %). m.p. > 300 °C. 

A. 2-( Bromomethyl)- .-( ehloromethyD-1, -dioxane. A 100-mL, round-bottomed flask is equipped with a 10-mL Dean-Stark apparatus and a condenser. The flask is charged with 30.0 g (0.138 mol) of l-bromo-3-chloro-2,2-dimethoxypropane (Note 1), 10.0 mL (0.138 mol) of 1,3-propanediol (Note 2), and 3 drops of concentrated sulfuric acid. The resulting solution is heated (bath temperature 140°C) for 8 hr (Note 3) with distillative removal of methanol (ca. 11 mL). The mixture is allowed to cool to room temperature and the crude product is partitioned in 150 mL of pentane and 40 mL of water. The... 

Secondary amines react with ketones that contain an H atom in the a position through an addition and subsequent El elimination to form enamines (Figure 7.27). In order for enamines to be formed at all in the way indicated, one must add an acid catalyst. In order for them to be formed completely, the released water must be distilled off azeotropically. The method of choice for preparing enamines is therefore to heat a solution of the carbonyl compound, the amine, and a catalytic amount of tolu-enesulfonic acid in cyclohexane to reflux in an apparatus connected to a Dean-Stark trap. 

It may also help to distil out the water that is formed in the reaction diethyl adipate (the diethyl ester of hexanedioic add) can be made in toluene solution using a sixfold excess of ethanol, concentrated H2SO4 as catalyst, distilling out the water using a Dean Stark apparatus. You can tell from the yield that the equilibrium is very favourable. 

When a mixture of toluene and water boils, the vapour produced is a constant ratio mixture of toluene vapour and water vapour known as an azeotrope. If this mixture is condensed, the liquid toluene and water, being immiscible, separate out into two layers with the water below. By using a Dean Stark apparatus, or Dean Stark head, the toluene layer can be returned to the reaction mixture while the water is removed. Reactions requiring removal of water by distillation are therefore often carried out in refluxing toluene or benzene under a Dean Stark head. 

The water content is determined by azeotropic distillation in the Dean-Stark apparatus. ... 

Synthesis of polymer-supported Pd catalyst [44] For the synthesis of polymer 41, see refs. [46-48]. All solvents vs ere degassed by ultrasonication and argon purging prior to use. To a -well-stirred solution of 44 (0.36 mmol in phosphine) in THF (72 mb) was added a solution of 45 (0.12 mmol) in H2O (30 mb) and the mixture was again degassed. After the mixture had been stirred for 62 h at room temperature, a yellow precipitate formed. Water (30 mb) was added to the suspension, and THF was removed at 80 °C by distillation for 4 h in an apparatus fitted with a Dean-Stark head to leave a reddish precipitate. This precipitate was stirred at 100 °C, first in H2O (100 mb) for 12 h, then in THF (100 mb) for 3 h, and finally in further H2O (100 mb) for 12 h to wash away the unreacted palladium species and polymers. After drying in vacuo (ca. 0.1 mmHg), 41 was obtained as a dark-red solid in almost quantitative yield. 

One of the first reactions carried out in perfluorinated solvents was the transesterification described by Zhu in 1993 [10]. He used the perfluorinated solvent FC-77 (mainly perfluoro-2-butyltetrahydrofuran) for an azeotropic distillation of the formed methanol or propanol in the transesterification of methyl- or pro-pylesters 1 with different alcohols 2 using a Dean-Stark apparatus Eq. (1). 

Washing and extraction steps are made easier or even suppressed. In the case of equilibrated reactions leading to light polar molecules (MeOH, EtOH or H2O), equilibrium can be easily shifted by a simple heating just above the boiUng points or under reduced pressure. With the usual procedure this operation is impeded by the presence of solvent necessitating an azeotropic distillation using a Dean-Stark apparatus [Eq. (2)]. 

A suspension of freshly activated MTS or silica gel (1 or 4) in toluene was refluxed and stirred for 2 h with CPS under dry nitrogen. After distillation in a Dean-Stark collector of a fraction of toluene containing methanol (or ethanol), the mixture was again heated at toluene refluxing temperature for 2 h and the distillation sequence was repeated. The modified solid was filtered, extracted in a sohxlet apparatus for 24 h with methanol, then dried at 100°C (solids 2a, b or 5a,... 

Protection of the Aldehyde. A mixture of o-anisaldehyde (13.6 g, 100 mmoles), ethylene glycol (7.4S g, 120 mmoles), and p-toluenesulfonic acid (0.3 g) is refluxed with benzene in a Dean-Stark apparatus until no starting aldehyde can be detected by TLC ( 6 hr). After being cooled, the benzene solution is washed three times with 5% aqueous NaHC03, then with saturated salt water until the washings are neutral, and then dried over Na2SOa. The solvent is removed under vacuum and the product collected in 96% yield by vacuum distillation (80°, 1 torr Hg). 

A mixture of di- -butyltin oxide, phenol, and tetralin stirred and refluxed 3.5 hrs. at 225-240° bath temp, until the theoretical amount of water has evolved di-rt-butyltin diphenoxide. Y 84%. - A Dean-Stark apparatus with xylene in the side arm is used because the organic phase of the distillate is denser than water. F. e. s. R. G. Rees and A. F. Webb, J. Organometal. Chem. 12, 239 (1968). 

A mixture of 14.92 g /7-A,A -dimethylaminobenzaldehyde (0.1 mol), 4.45 g ethanol-amine, and 50 mL dry benzene in a Dean-Stark moisture determination apparatus was refluxed in an oil bath until the volume of water collected in the trap remained constant (2-3 h). The benzene was removed by distillation under reduced pressure, and the residual oil was poured onto an ice-water mixture. The solid crystalline mass was triturated with cold water, collected on a suction filter, and washed on the filter with several portions of cold water. After drying the crystals on the filter by use of a rubber dam followed by air drying, the crude material was dissolved in boiling petroleum ether (b.p. 30-60°C), treated with Norite A for 15 min, and filtered. The filtrate was cooled in an ice-water bath to induce crystallization. The crystals were collected on a suction filter and washed with several small portions of cold petroleum ether, in a yield of 57%, m.p. 103-104°C. 

After all the components have been thoroughly dried in an oven, the apparatus is assembled as shown. Dried xylene is added to the Morton flask and heated to reflux any traces of residual moisture are removed by distilling over several milliliters and removing any azeotrope that forms in the Dean-Stark trap. Anhydrous rerr-butyl alcohol is added to the flask, followed by potassium metal. The solution is stirred, and after all the potassium has reacted and the solution is boiling vigorously, slow addition of diethyl tetradecan-l,14-dicarboxylate from the Hershberg funnel is started. The solvent vapors, which condense and fall into the dilution chamber, dilute the diester and carry it into the Morton flask where the reaction occurs. An ethanol-xylene mixture is removed via the Dean-Stark trap at approximately the same rate as the solution is added from the dropping funnel. A slow continuous addition of the ester maximizes the probability of cyclization a typical reaction time is 24 hr. 

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