Sodium carbonate solutions

Ethyl bromide soon distils over, and collects as heavy oily drops under the water in the receiving flask, evaporation of the very volatile distillate being thus prevented. If the mixture in the flask A froths badly, moderate the heating of the sand-bath. When no more oily drops of ethyl bromide come over, pour the contents of the receiving flask into a separating-funnel, and carefully run oflF the heavy lower layer of ethyl bromide. Discard the upper aqueous layer, and return the ethyl bromide to the funnel. Add an equal volume of 10% sodium carbonate solution, cork the funnel securely and shake cautiously. Owing to the presence of hydrobromic and sulphurous acids in the crude ethyl bromide, a brisk evolution of carbon dioxide occurs therefore release the... 

Reactions of Picric Acid, (i) The presence of the three nitro groups in picric acid considerably increases the acidic properties of the phenolic group and therefore picric acid, unlike most phenols, will evolve carbon dioxide from sodium carbonate solution. Show this by boiling picric acid with sodium carbonate solution, using the method described in Section 5, p. 330. The reaction is not readily shown by a cold saturated aqueous solution of picric acid, because the latter is so dilute that the sodium carbonate is largely converted into sodium bicarbonate without loss of carbon dioxide. 

For dehydrogenation, add this ester to dilute nitric acid (20 ml. of the concentrated acid diluted with 40 ml. of water) and boil the mixture under reflux for about 5 minutes, during which the ester gently efferv esces and Anally gives a clear solution. Cool this solution in ice-w ater, make alkaline with aqueous sodium carbonate solution and extract tw ice with ether (50 ml. for each extraction). Dry the extract with sodium sulphate, filter, and then distil using a small distilling-flask... 

The Bart reaction can be carried a stage further. For example, dichloro-phenylarsine, CjHjAsCl, when added to an excess of sodium carbonate solution, gives CjHjAsfONa) this solution, if similarly treated with benzenedia-zonium chloride, affords diphenylarsinic acid, (CjHjjjAsf. OjOH. 

Section 5. Treatment with Sodium Carbonate solution. 

Sodium carbonate solution [cf. Section 5, p. 330). Note that phenols (except those containing acidic groups, e.., nitrophenols) give no reaction with sodium carbonate solution. 

Solubility in sodium carbonate solution. Note that phenols, when soluble in water, will also dissolve in NagCOg solution, but usually loithout evolution of CO, i.e., without the formation of a sodium derivative. This reaction can therefore be used to distinguish between carboxylic adds and most phenols. See Section 5, p. 330. 

This tube is connected %vith rubber tubing of about 6 mm. bore to the carbon dioxide Kipp, via a wash-bottle containing sodium carbonate solution (to remove any dilute hydrochloric acid spray). It is very important, when the apparatus is in use, that there should be no constriction or bend in the rubber tube between the tap C and the wash-bottle. If these precautions are taken, a slow, e en, and easily controlled flow of gas can be obtained. 

This type of extraction depends upon the use of a reagent which reacts chemically with the compound to be extracted, and is generally employed either to remove small amounts of impurities in an organic compound or to separate the components of a mixture. Examples of such reagents include dilute (5 per cent.) aqueous sodium or potassium hydroxide solution, 5 or 10 per cent, sodium carbonate solution, saturated sodium bicarbonate solution (ca. 5 per cent.), dilute hydrochloric or sulphuric acid, and concentrated sulphuric acid. 

Dilute sodium hydroxide solution (and also sodium carbonate solution and sodium bicarbonate solution) can be employed for the removal of an organic acid from its solution in an organic solvent, or for the removal of acidic impurities present in a water-insoluble solid or liquid. The extraction is based upon the fact that the sodium salt of the acid is soluble in water or in dilute alkali, but is insoluble in the organic solvent. Similarly, a sparingly soluble phenol, e.g., p-naphthol, CioH,.OH, may be removed from its solution in an organic solvent by treatment with sodium hydroxide solution. 

Methylene chloride. The commercial substance is purified by washing with 5 per cent, sodium carbonate solution, followed by water, dried over anhydrous calcium chloride, and then fractionated. The fraction, b.p. 40-41°, is collected. 

All hydrocarbons prepared by th -. Wurtz reaction contain small quantities of unsaturated hydrocarbons. These may be removed by shaking repeatedly with 10 pier cent, of the volume of concentrated sulphuric acid until the acid is no longer coloured (or is at most extremely pale yellow) each shaking should be of about 5 minutes duration. The hydrocarbon is washed with water, 10 pier cent sodium carbonate solution, water (twice), and dried with anhydrous magnesium or calcium sulphate. It is then distilled from sodium two distillations are usually necessary... 

Commercial diethyl carbonate may be purified by the following process. Wash 100 ml. of diethyl carbonate successively with 20 ml. of 10 per cent, sodium carbonate solution, 20 ml. of saturated calcium chloride solution, and 25 ml. of water. Allow to stand for one hour over anhydrous calcium chloride with occasional shaking, filter into a dry fiask containing 5 g. of the same desiccant, and allow to stand for a further hour. Distil and collect the fraction boiling at 125-126°. Diethyl carbonate combines with anhydrous calcium chloride slowly and prolonged contact should therefore be avoided. Anhydrous calcium sulphate may also be used. 

Allyl Bromide. Introduce into a 1-litre three-necked flask 250 g. (169 ml.) of 48 per cent, hydrobromic acid and then 75 g. (40-5 ml.) of concentrated sulphuric acid in portions, with shaking Anally add 58 g. (68 ml.) of pure allyl alcohol (Section 111,140). Fit the flask with a separatory funnel, a mechanical stirrer and an efficient condenser (preferably of the double surface type) set for downward distillation connect the flask to the condenser by a wide (6-8 mm.) bent tube. Place 75 g. (40 5 ml.) of concentrated sulphuric acid in the separatory funnel, set the stirrer in motion, and allow the acid to flow slowly into the warm solution. The allyl bromide will distil over (< 30 minutes). Wash the distillate with 5 per cent, sodium carbonate solution, followed by water, dry over anhydrous calcium chloride, and distil from a Claisen flask with a fractionating side arm or through a short column. The yield of allyl bromide, b.p. 69-72°, is 112 g. There is a small high-boiling fraction containing propylene dibromide. 

Dibromobutane from 1 4 butanediol). In a 500 ml. threenecked flask fltted with a stirrer, reflux condenser and dropping funnel, place 154 g. (105 ml.) of 48 per cent, hydrobromic acid. Cool the flask in an ice bath. Add slowly, with stirring, 130 g. (71 ml.) of concentrated sulphuric acid. To the resulting ice-cold solution add 30 g. of redistilled 1 4-butanediol dropwise. Leave the reaction mixture to stand for 24 hours heat for 3 hours on a steam bath. The reaction mixture separates into two layers. Separate the lower layer, wash it successively with water, 10 per cent, sodium carbonate solution and water, and then dry with anhydrous magnesium sulphate. Distil and collect the 1 4-dibromo-butane at 83-84°/12 mm. The yield is 55 g. 

Mix 30 g. (38 ml.) of iaopropyl alcohol with 450 g. (265 ml.) of constant boiling point hydriodic acid (57 per cent.) (Section 11,49,2) in a 500 ml. distilling flask, attach a condenser for downward distillation, and distil slowly (1-2 drops per second) from an air bath (compare Fig. II, 5, 3). When about half the liquid has passed over, stop the distillation. Separate the lower layer of crude iodide (80 g.). Redistil the aqueous layer and thus recover a further 5 g. of iodide from the flrst quarter of the distillate (1). Wash the combined iodides with an equal volume of concentrated hydrochloric acid, then, successively, with water, 5 per cent, sodium carbonate solution, and water. Dry with anhydrous calcium chloride and distil. The isopropyl iodide distils constantly at 89°. 

Add 1 ml. of the alcohol-free ether to 0-1-0-15 g. of finely-powdered anhydrous zinc chloride and 0 5 g. of pure 3 5-dinitrobenzoyl chloride (Section 111,27,1) contained in a test-tube attach a small water condenser and reflux gently for 1 hour. Treat the reaction product with 10 ml. of 1-5N sodium carbonate solution, heat and stir the mixture for 1 minute upon a boiling water bath, allow to cool, and filter at the pump. Wash the precipitate with 5 ml. of 1 5N sodium carbonate solution and twice with 6 ml. of ether. Dry on a porous tile or upon a pad of filter paper. Transfer the crude ester to a test-tube and boil it with 10 ml. of chloroform or carbon tetrachloride filter the hot solution, if necessary. If the ester does not separate on cooling, evaporate to dryness on a water bath, and recrystallise the residue from 2-3 ml. of either of the above solvents. Determine the melting point of the resulting 3 5 dinitro benzoate (Section 111,27). 

Treat a small quantity of the bisulphite addition compound with 5 ml. of 10 per cent, sodium carbonate solution, and note the odour. Repeat the experiment with 5 ml. of dilute hydrochloric acid. 

The bisulphite solution obtained by passing sulphur dioxide into sodium carbonate solution is not recommended since the resulting yellow solution contains free sulphurous asid which dissolves some bisulphite compounda... 

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