Calcium chloride tube

Lead formate separates from aqueous solution without water of crystallisation. It can therefore be used for the preparation of anhydrous formic acid. For this purpose, the powdered lead formate is placed in the inner tube of an ordinary jacketed cond ser, and there held loosely in position by plugs of glass-wool. The condenser is then clamped in an oblique position and the lower end fitted into a receiver closed with a calcium chloride tube. A current of dry hydrogen sulphide is passed down the inner tube of the condenser, whilst steam is passed through the jacket. The formic acid which is liberated... 

Place 0 5 ml. of the pyridine in a 200 ml. round- or flat-bottomed flask and add 34 ml. (30 g.) of benzene. Fit the flask with a reflux water-condenser, and then place it in a cold water-bath. If the experiment is conducted in a fume-cupboard, the top of the condenser can be closed with a calcium chloride tube bent downwards (as in Fig. 61, p. 105 or in Fig. 23(A), p. 45, where the outlet-tube A will carry the calcium chloride tube) and the hydrogen bromide subsequently allowed to escape if, however, the experiment is performed in the open laboratory, fit to the top of the condenser (or to the outlet-tube A) a glass delivery-tube which leads through a piece of rubber tubing to an inverted glass funnel, the rim of which dips just below the surface of some water... 

For this preparation, which must be performed in the fume-cupboard, assemble the apparatus shown in Fig. 67(A). C is a 150 ml. distilling-flask, to the neck of which is fitted a reflux single-surface water-condenser D, closed at the top E by a calcium chloride tube. The side-arm of C carries a cork F which fits the end E of the condenser for subsequent distillation. The side-arm of C is meanwhile plugged by a small rubber cork, or by a short length of glass rod. (Alternatively, use the ground-glass flask and condenser (Fig. 22 (a) and (c), p. 43), and... 

Place 20 g. of dry powdered benzoic acid in C, add 15 ml. (25 g., i.e., a 30% excess) of thionyl chloride and some fragments of porcelain, and then clamp the apparatus on a boiling water-bath as shown so that no liquid can collect in the side-arm of C. Heat for one hour (with occasional gentle shaking), by which time the evolution of gas will be complete. Cool the flask C, detach the condenser and fit it to the side-arm for distillation, using a 360° thermometer for the neck of C. To the lower end of the condenser fit a small conical flask G (Fig. 67(B)) by a cork carrying also a calcium chloride tube. 

In place of the conical flask G, a small Buchner flask may be used with the calcium chloride tube fitted to the side-arm, but in either case a duplicate flask for the second fraction should be available. 

Assemble in a fume-cupboard the apparatus shown in Fig. 67(A). Place 15 g. of 3,5-dinitrobenzoic acid and 17 g. of phosphorus pentachloride in the flask C, and heat the mixture in an oil-bath for hours. Then reverse the condenser as shown in Fig. 67(B), but replace the calcium chloride tube by a tube leading to a water-pump, the neck of the reaction-flask C being closed with a rubber stopper. Now distil off the phosphorus oxychloride under reduced pressure by heating the flask C in an oil-bath initially at 25-30, increasing this temperature ultimately to 110°. Then cool the flask, when the crude 3,5-dinitro-benzoyl chloride will solidify to a brown crystalline mass. Yield, 16 g., i.e,y almost theoretical. Recrystallise from caibon tetrachloride. The chloride is obtained as colourless crystals, m.p. 66-68°, Yield, 13 g Further recrystallisation of small quantities can be performed using petrol (b.p. 40-60°). The chloride is stable almost indefinitely if kept in a calcium chloride desiccator. 

Fit a 750 ml, bolt-head flask (also by a rubber stopper) to a reflux water-condenser closed at the top by a calcium chloride tube ensure that flask and condenser are quite dr). Place 150 ml. of the dried ethyl acetate in the flask and add 15 g. of sodium. The sodium for this purpose should preferably be added in the form of wire directly from a sodium press (Fig. 55, p. 82) alternatively the sodium may be added as thin slices, but in this case each slice should be quickly pressed between drying-paper before being added to the acetate to remove the wet film which may have formed during the weighing and cutting of the metal. 

Refractionation of the low-boiling impurities gives a further quantity of the acetoacetate, but if the initial distillation has been carefully conducted, the amount recovered is less than i g., and the refractionation is not worth while. If possible, complete the preparation in one day. If this is not possible, it is best to allow the cold crude sodium derivative (before acidification) to stand overnight, the flask being closed by a cork carrying a calcium chloride tube the yield will now fall to about 38 g. Alternatively, the crude ester may be allowed to remain overnight in contact with the sodium sulphate, but in this case the yield will fall to about 30 g. 

Fit a 50 ml. round-bottomed flask to a reflux water-condenser fitted with a calcium chloride tube. Dissolve 1-05 ml. of dry bromobenzene in 5 ml. of dry ether and add this solution to 0-25 g. of magnesium contained in the round-bottomed flask. Now add a crystal of iodine so that it rests on the magnesium. Warm if necessary to start the reaction if the latter becomes too vigorous immerse the flask in cold... 

Assemble an apparatus similar to that used in the prenous experiment, i.e., a 500 ml. conical flask fitted at the neck with a freshly-charged calcium chloride tube, a dropping-funnel, and in addition an outlet-tube joined to the water-pump so that dry air can be drawn through the calcium chloride tube and thence through the conical flask. The purpose of the air-stream is to remove as much as possible of the excess of hydrogen chloride. 

Place 38 ml. of isopropanol in a two-necked 500 ml. round-bottomed flask fitted with (a) a reflux water-condenser having a calcium chloride tube at the top, and (b) a dropping-funnel. Cool the flask in ice-water and then run 13 5 ml. of phosphorus trichloride in from the dropping-funnel during 15 minutes. Then allow the reaction-mixture to attain room temperature. Now replace the condenser and the... 

Two forms of the so called calcium chloride tubes (also termed drying tubes, straight form) are shown in (c) and (d) these are fiUed with anhydrous calcium chloride or with cotton wool (previously dried at 100°), and are attached by means of a stopper to a flask or apparatus containing substances from which moisture is to be excluded. 

Absorbent cotton (cotton wool). This material is an excellent drying agent for use in the so-called calcium chloride tubes, i.e., drying tubes, placed at the top of dropping funnels, reflux condensers, etc., to exclude moisture. It is more convenient than calcium chloride, and should preferably be dried in an oven at 100° before use. 

Method 1. Use the apparatus depicted iu Fig. Ill, 56, 1, but omit the thermometer also attach a cotton wool (or calcium chloride) tube to the side arm of the filter fiask receiver in order to prevent the entrance of moisture into the apparatus. Mount the reaction fiask in a water bath e.g., a large beaker or other convenient vessel). It is important that all the apparatus be perfectly dry, since both phosphorus trichloride and acetyl chloride are decomposed by water. The set-up should be assembled in the fume eupboard. 

Dissolve 57 g. of dry malonic acid in 92 5 ml. of dry P3rridine contained in a 500 ml. round-bottomed flask, cool the solution in ice, and add 57 g. (70 ml.) of freshly distilled n-heptaldehyde (oenanthol) with stirring or vigorous shaking. After a part of the aldehyde has been added, the mixture rapidly seta to a mass of crystals. Insert a cotton wool (or calcium chloride) tube into the mouth of the flask and allow the mixture to stand at room temperature for 60 hours with frequent shaking. Finally, warm the mixture on a water bath until the evolution of carbon dioxide ceases (about 8 hours) and then pour into an equal volume of water. Separate the oily layer and shake it with 150 ml. of 25 per cent hydrochloric acid to remove pyridine. Dissolve the product in benzene, wash with water, dry with anhydrous magnesium sulphate, and distil under reduced pressure. Collect the ap-nonenoic acid at 130-13272 mm. The yield is 62 g. 

Dihydroxyacetophenone. Finely powder a mixture of 40 g. of dry hydroquinone diacetate (1) and 87 g. of anhydrous aluminium chloride in a glass mortar and introduce it into a 500 ml. round-bottomed flask, fitted with an air condenser protected by a calcium chloride tube and connected to a gas absorption trap (Fig. II, 8, 1). Immerse the flask in an oil bath and heat slowly so that the temperature reaches 110-120° at the end of about 30 minutes the evolution of hydrogen chloride then hegins. Raise the temperature slowly to 160-165° and maintain this temperature for 3 hours. Remove the flask from the oil bath and allow to cool. Add 280 g. of crushed ice followed by 20 ml. of concentrated hydrochloric acid in order to decompose the excess of aluminium chloride. Filter the resulting solid with suction and wash it with two 80 ml. portions of cold water. Recrystallise the crude product from 200 ml. of 95 per cent, ethanol. The 3 ield of pure 2 5-dihydroxyacetophenone, m.p. 202-203°, is 23 g. 

In a i-l. three-necked, round-bottom flask fitted with a mechanical stirrer through a mercury seal, a separatory funnel and an efficient reflux condenser to which a calcium chloride tube is attached, are placed 25 g. (1.03 moles) of magnesium turnings 140 cc. of dry ether, and a small crystal of iodine. The stirrei is started and a small portion (about 10 cc.) of a solution of 118.5 g. (i mole) of cyclohexyl bromide (Note i) in 120 cc. of dry ether is added through the separatory funnel. After the reaction starts, the remainder of the solution is run in at such a rate that the whole is added at the end of forty-five minutes. The mixture is stirred and refluxed for an additional thirty to forty-five minutes. 

A MIXTURE of 120 g. (3 moles) of sodamide (Note i) and 200 cc. of purified mineral oil (Note 2) is ground together in a mortar until the amide is finely pulverized (Note 3). This suspension is transferred to a 2-I. round-bottom, three-necked flask fitted with a reflux condenser holding a calcium chloride tube, a 500-cc. separatory funnel, and an efficient mechanical stirrer through a mercury seal. The mortar and pestle are rinsed with an additional 250 cc. of the oil which is then added to the reaction flask. This is heated in an oil bath maintained at 160-165, the stirrer is started and 203 g. (i mole) of cyclohexylbromopropene (p. 20) is dropped in during one and one-half hours. Ammonia is evolved and this is allowed to pass through the condenser and is collected in water. 

In a 5-I. round-bottom flask, fitted with a stirrer, separatory funnel and a reflux condenser to the upper end of which a calcium chloride tube is attached, is placed 150 g. of magnesium turnings. A small crystal of iodine (Note i) and about 100 cc, of a mixture of 822 g. (6 moles) of M-butyl bromide and 2 1. of anhydrous ethyl ether are added. As soon as the reaction starts, 350 cc. of anhydrous ether is added and the remainder of the -butyl bromide solution is dropped in at such a rate that the mixture boils continuously. The time of addition (one and one-half hours) may be decreased by cooling the flask externally. Stirring is started as soon as enough liquid is present in the flask. 

A mixture of 56.8 g (0.21 mol) of diphenyl phosphorochloridate (Note 1), 16.3 g (0.25 mol) of sodium azide, and 300 mL of anhydrous acetone (Note 2) in a 500-mL round-bottomed flask fitted with a calcium chloride tube is stirred at 20-25°C for 21 hr. The lachrymatory mixture is filtered in a hood, and the filtrate is concentrated under reduced pressure. The residue is distilled through a short Vigreux column (Note 3). The yield of diphenyl phos-phorazidate, bp 134-136 C (0.2 ram), is 49-52 g (84-89 ) (Note 4). 

The crude enamlne (1) is dissolved in 20 mL of toluene, and the solution is transferred (Note 3) to a 100-mL, three-necked flask equipped with a magnetic stirring bar, 50-mL dropping funnel, reflux condenser protected with a calcium chloride tube, and a thermometer immersed in the solution. A solution of 13.2 g (0.048 mol) of diphenyl phosphorazidate (Note 4 uarntng) in 20 mL of toluene is added with stirring during 30 min di11e the reaction temperature is maintained at about 25°C. The mixture is stirred for 4 hr at 25 C and heated at reflux for 1 hr. The mixture is transferred to a 300-mL, round-bottomed flask and most of the toluene is removed under reduced pressure to yield 23.7 g of a reddish-brown oil, 2 (Note 5). 

I. The 500 cc. of absolute alcohol is cooled in an ice bath and treated with dry hydrogen chloride until 163 g. has been added, an amount sufficient for saturation. The solution should be protected from the moisture of the air with a calcium chloride tube. 

A. Ester condensation. A suspension of 9.40 g. (0.41 gram atom) of powdered sodium in 100 ml. of absolute ether is placed in a 1-1. three-necked flask (Note 1) fitted with a reflux condenser, dropping funnel, and a calcium chloride tube. A solution of 23.8 ml. (0.41 mole) of absolute alcohol (Note 2) in 50 ml. of abso-... 

The considerable quantities of hydrogen chloride and hydrogen bromide evolved are best handled by means of a gas-absorption trap.- The insertion of a calcium chloride tube between the trap and the reflux condenser is recommended. 

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