Distilling Heads

Round-bottomed flasks (Fig. 22(A)) of various sizes and having necksof various lengths and widths. They can be closed with stoppers (Fig. 22(B)), or fitted with any of the following units reflux air-condensers (Fig. 22(C)) or water condensers (Fig. 22(D)) distillation heads, of the simple knee-tube type (Fig. 22(E)), or with a vertical joint (Fig. 22(F)) for thermometers, etc., or with... 

The distillation heads Fig. 22(F) and Fig. 22(G) can be fitted with thermometers having a ground-glass cone just above the bulb (Fig. 22(M)). These are expensive, and it is usually more convenient to fit a thermometer pocket (Fig. 22(N)) which consists of a small well , fitting as shown into the neck of the flask. A small volume of mercury is placed in the well just to cover the bulb of a conventional thermometer, and thus provides excellent thermal contact between the thermometer and the sides of the pocket. 

Fit a 500 ml. bolt-head flask F with a well-fitting cork which is free from flaws, and which carries a dropping-funnel D and a delivery tube (or knee-tube ) T, the latter being connected to a water-condenser C (Fig. 52). Attach an adaptor A to the lower end of the condenser. (Alternatively, use a ground-glass flask (Fig. 22(a), p. 43) with a distillation-head (Fig. 22(F)) the dropping-funnel can be fitted into the distillation-head, the side-arm of which is connected to a condenser as in Fig. 23(0), p. 45.)... 

Pour the mixture into a 500 ml. flask fitted with a steam-distillation head, and with a steam-inlet tube reaching almost to the bottom of the flask. First distil off the benzene in steam. Then place the flask in an oil-bath heated to 165-170 ", and continue the steam-distillation (2-3 hours). The /)-bromobiphenyl passes over and forms orange crystals in the water-condenser therefore run the water out of the condenser for a short while from time to time to melt the orange deposit and allow it to run into the receiver containing the distilled water. 

Prepare a mixture of 30 ml, of aniline, 8 g. of o-chloro-benzoic acid, 8 g. of anhydrous potassium carbonate and 0 4 g. of copper oxide in a 500 ml. round-bottomed flask fitted with an air-condenser, and then boil the mixture under reflux for 1 5 hours the mixture tends to foam during the earlier part of the heating owing to the evolution of carbon dioxide, and hence the large flask is used. When the heating has been completed, fit the flask with a steam-distillation head, and stcam-distil the crude product until all the excess of aniline has been removed. The residual solution now contains the potassium. V-phenylanthrani-late add ca. 2 g. of animal charcoal to this solution, boil for about 5 minutes, and filter hot. Add dilute hydrochloric acid (1 1 by volume) to the filtrate until no further precipitation occurs, and then cool in ice-water with stirring. Filter otT the. V-phcnylanthranilic acid at the pump, wash with water, drain and dry. Yield, 9-9 5 g. I he acid may be recrystallised from aqueous ethanol, or methylated spirit, with addition of charcoal if necessary, and is obtained as colourless crystals, m.p. 185-186°. 

When the reaction has subsided, boil the reaction-mixture under reflux for 2 hours then make it alkaline with sodium hydroxide solution, and distil it in steam until oily drops no longer come over in the aqueous distillate (1 2 litres). Extract the distillate thoroughly with ether ca. 150 ml.), and dry the ethereal extract over powdered sodium hydroxide. Filter the dry extract through a fluted filter-paper moistened with ether into a 200 ml. flask. Fit the flask with a distillation-head, or a knee-tube , and distil off the ether. Now replace the distillation-head by a reflux water-condenser, add 10 ml. of acetic anhydride, and boil the mixture under reflux for 10 15 minutes. 

Distillation heads (or still heads). Fig. II, 56, 5 is a bend ( knee tube ), which is frequently employed for distillation. Convenient sizes are bottom cone 19, 24, 29 or 34 side cone 19 or 24. 

Fig. II, 56, 6 is a simple distillation head when this is fitted into a flask with a ground glass socket, the assembly is virtually a distillation flask. The bottom cone is usually 19, 24 or 29 the side cone is generafly B19 but may be 24 the thermometer socket is 14. For many purposes, a thermometer is fitted into a one-hole rubber stopper of correct taper and then inserted into the 14 socket the area of rubber which is exposed to the action of the organic vapour is relatively so small that the amount of contamination thus introduced is negligible. If, however, all rubber stoppers must be absent because of the highly corrosive character of the vapour, a thermometer with a 14 cone is employed. It is important to have the thermometer of the same glass as the distillation head, otherwise difficulties may arise owing to the different expansion coefficients of the two kinds of glass.

Fig. 11, 56, 7 is a Claisen distillation head. The lower cone is usually B19 or 24 and the side cone is generally 19 (sometimes 24) thesockets... 

To a 3QQ-mL, round-bottomed flask fitted with a water separator, (Note 1) which contains 15 g of Linde 4A molecular sieve l/16-1nch pellets and Is filled with toluene, are added 7.3 g (0.04 mol) of cyclododecanone, 11.4 g (0.16 mol) of pyrrolidine, 100 mL of toluene, and 0.57 g (0.004 mol) of boron trifluoride etherate. The solution is heated under reflux for 20 hr. The water separator is replaced by a distillation head, and about 90 mL of the toluene is removed by distillation at atmospheric pressure. The residue containing l-(N-pyrrolidino)-l-cyclododecene (1) is used in the next step without further purification (Note 2). 

In a 2-1. flask fitted with a total-reflux, variable-take-off distillation head is placed a solution of 53 g. (0.472 mole) of dihydroresorcinol (Note 1), 2.3 g. of -toluenesulfonic acid monohydrate and 250 ml. of absolute ethanol in 900 ml. of benzene. The mixture is heated to boiling and the azeotrope composed of benzene, alcohol, and water is removed at the rate of 100 ml. per hour. When the temperature of the distilling vapor reaches 78° (Note 2), the distillation is stopped and the residual solution is washed with four 100-ml. portions of 10% aqueous sodium hydroxide which have been saturated with sodium chloride. The resulting organic solution is washed with successive 50-ml. portions of water until the aqueous washings are neutral and then concentrated under reduced pressure. The residual liquid is distilled under reduced pressure. The yield of 3-ethoxy-2-cyclohexenone (Note 3), b.p. 66-68.5°/0.4 mm. or 115-121°/11 mm., Mq 1.5015, is 46.6-49.9 g. (70-75%). 

Tetraethyl orthosilicate (104.2 g) and deuterium oxide (40 g) are stirred in a stoppered distillation flask at room temperature until a viscous, miscible solution is obtained (approximately 24 hr). (A small amount of acid catalyst, such as deuteriochloric acid, speeds up the reaction considerably. ) A distillation head and a receiver cooled in a dry ice-acetone bath are attached and the solution is distilled at 2 mm pressure until no further product is obtained. A 90% yield of ethanol-OD is obtained having an isotopic purity equal to that of the deuterium oxide used. ... 

The reaction vessel is cooled to 30° and the reflux condenser replaced with a distillation head and condenser. The methylene chloride is removed by distillation, b.p. 35-55°. The residue is then transferred to a 500-ml. round-bottomed flask and distilled through a 30-cm. Vigreux column. The yield of a-chloroanisole is 266-271 g. (93-95%), b.p. 74-77° (13 mm.), w23d 1.5342 (Notes 5, 6, 7). 

In a 2-1 three-necked flask equipped with a stirrer, a reflux condenser, and a dropping funnel (Note 1) 832 g (4 0 moles) of phosphorus pentachloride is stirred with 250 ml. of phosphorus oxychloride (Note 2) To this is added with stirring 264 g (272 ml, 4 4 moles) of methyl formate (Note 3). During the addition the reaction vessel is cooled in an ice bath to maintain a reaction temperature of 10-20° The addition requires about 1.75 hours When the addition is complete, the solution is stirred at a temperature under 30° until all the phosphorus pentachloride has dissolved (about 1 hour) Then the stirrer is removed, the reflux condenser is replaced by a distilling head, and the reaction... 

In a 1-1. round-bottomed flask equipped with a condenser are placed 78.0 g. (0.56 mole) of commercial anhydrous potassium arbonate, 45.0 g. (0.50 mole) of methallyl chloride (Note 1), 55.0 g. (0.55 mole) of 2,4-pentanedione (Note 1), and 300 ml. of anhydrous ethanol (Note 2). The mixture is refluxed on a steam bath for 16 hours. The condenser is replaced by a distilling head and condenser, and about 200 ml. of ethanol is distilled from the mixture (Note 3). Ice water (600 ml.) is added to dissolve the salts, and the mixture is extracted three times with ether. The... 

Adipic acid, 219.2 g (1.5 mol), and 77.6 g (1.25 mol) of 1,2-ethanediol are weighed into a 500-mL glass reactor equipped with a mechanical stirrer, a nitrogen inlet, and a distillation head connected to a condenser and a receiver fiask. The reactor is placed in a salt bath preheated at 180°C and the temperature is dien raised gradually to 220°C (see note at end of procedure) until the greater part of water has been removed (3 h). The reactor is cooled down to 160°C and vacuum is applied slowly to ca. 0.07 mbar (30 min). Temperature is ramped to 220°C (see note below) at a rate of l°C/min and reaction is continued for an additional 90 min. At the end of reaction, the carboxylic acid endgroup content is close to 1.90 mol/kg. No purification of final polyester is carried out. 

Maleic anhydride, 98 g (1.0 mol), 148 g (1.0 mol) of phthalic anhydride, and 160 g (2.1 mol) of 1,2-propanediol are poly condensed in a three-necked flask equipped with a mechanical stirrer, a nitrogen inlet, and a distillation head connected to a condenser and a receiver flask. The flask is placed in a salt bath preheated at 160°C. Water begins to distill and the temperature is then raised gradually to 190°C. The polycondensation is stopped (after about 15 h) when the reaction mixture has an acid number of 50 (see Section 2.3.8.4.1) (Scheme 2.54). A slightly different procedure is described in ref. 423. 

Into a 1-L three-necked glass reaction kettle equipped with a mechanical stiner, nitrogen inlet tube, and a distillation head connected to a condenser are... 

A 250-mL, three-necked, round-bottomed flask equipped with stirrer and distillation head suitable for vacuum distillation is filled with 120 g of freshly distilled 2-pyrrolidone. The reaction mass is heated under nitrogen to 80° C. Flake potassium hydroxide (3.4 g) is then added. The water formed is rapidly distilled from the flask under 1 mbar pressure. The hot solution is then rapidly... 

The distillation was conducted in a 500-mL, round bottomed flask equipped with a magnetic stirring bar and a variable take-off distillation head. 

Cyclopentadiene was obtained by pyrolysis of dicyclopentadiene (pract., 90%) which was purchased from Fluka. Pyrolysis was carried out following the previously described general procedure.2, Dicyclopentadiene (80 mL) was placed in a round-bottomed flask equipped with a magnetic stirbar and a Vigreux column fitted with a distillation head through which cold water was circulated. The contents of the flask were slowly heated with stirring at 160°C in an oil bath, and ca. 60 mL of cyclopentadiene (bp 38-42°C) was collected in a receiver cooled in an ice-salt bath. The cyclopentadiene was used... 

Triflic acid (0.032 g) is added through a septum to a stirred mixture of 2,5-hex-andione 1487 (1.95 g, 0.017 mol) and HMDS 2 (7.4 mb, 0.035 mol) whereupon an exothermic reaction results and hexamethyldisiloxane 7 is removed by distillation through a short-path distillation head. When the reaction subsides (15 min) 81% pure 2,5-dimethylpyrrole 1494, b.p. 165 °C, is isolated by distillation [41]. 

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