Hydrochloric Acid - from Solid Sodium Chloride

8 Hydrochloric Acid - from Solid Sodium Chloride 

Problem Historically, hydrogen chloride gas has been produced by the reaction of sodium chloride and concentrated sulfuric acid. This reaction can be observed by students and can be interpreted as a proton transfer from H2S04 molecules to Cl- ions of sodium chloride (see Fig. 7.12). With the recognition of the colorless gas and the production of hydrochloric acid, both substances should be clearly differentiated and be appropriately described in a correct manner the HCl(aq) solution contains the involved ions, and of course the gas HCl(g) contains molecules. 

Material Gas developer apparatus, upright cylinder with glass cover, test tubes sodium chloride, concentrated sulfuric acid, universal indicator paper. 

Procedure Fill the gas developer under the fume hood with sulfuric acid and sodium chloride. Dropping the acid onto the solid salt develops a gas and fills the cylinder through air replacement. First check the gas with a damp universal indicator paper, place a little water and shake, test the solution with indicator paper. 

Observation The substances strongly react in the gas developer, the apparatus warms up, and a colorless gas appears. The gas forms a whitish vapor, it also has a very shocking odor. The damp indicator paper is colored bright red by the formed gas, same color appears in the solution. 

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To a stirred solution of 120 ml of methylene chloride, 18 ml of dry pyridine, and 5 ml of iodine pentafluoride maintained at —10°C to —20°C in a Dry Ice-carbon tetrachloride slurry is added a solution of 13.5 gm (0.1 mole) of cumyl-amine in 10 ml of methylene chloride over a 1 hr period. The reaction mixture is stirred for another hour at —10°C, and then for 1 hr at 0°. After this time, water is added to the reaction mixture and stirring is continued until the yellow solid which had formed is dissolved. The lower organic layer is separated and washed in turn with water, 1 N hydrochloric acid, a saturated sodium thiosulfate solution, and again with water. After drying with anhydrous magnesium sulfate and filtration, the product solution is partially evaporated by means of a rotary evaporator at a temperature below 30°C. The brown solid obtained on cooling is separated and recrystallized twice from methylene chloride yield 4.75 gm (17.9%), m.p. 86.9°-88.7°C. 

To a cooled solution of 3.4 g of 6a-fluoro-16a,17a-isopropylidenedioxypregna-l,4,9(ll)-trien-21-ol-3,20-dione in 20 ml of 9 1 chloroform pyridine is added in small portions 1.4 g of tosyl chloride. The reaction mixture is allowed to stand for 14 hours at 0°C and is then washed with dilute hydrochloric acid, water and sodium bicarbonate solution. The chloroform is removed by evaporation under reduced pressure and the residue is dissolved in acetone. This acetone solution is added to a refluxing suspension of 10 g of potassium fluoride in 50 ml of dimethylformamide. After refluxing for 5 hours, the mixture is cooled and poured into water. The solid which forms is collected by filtration, dried and recrystallized from acetone and hexane to yield 6a,21-difluoro-16a,17a-isopropylidenedioxypregna-l,4,9 (ll)-triene-3,20-dione, M.P. 267°C (dec.), [a]D = +9°. 

To obtain free sulfonic acids from their sodium salts it is usual to stir the solid sodium salt with concentrated hydrochloric acid, filter off the precipitated sodium chloride on a sinter, and evaporate the filtrate in a vacuum the residue consists of the free sulfonic acid as a syrup or a hygroscopic crystal mass which can be freed from small amounts of salt and impurities by dissolution in ethanol. Free sulfonic acids can be obtained with certainty by treating the barium salts with sulfuric acid or the lead salts with sulfuric acid or hydrogen sulfide. 

Add 4.5 mL of concenfrafed hydrochloric acid to the distillate and transfer the mixture to a separatory funnel. Check the pH of the mixture to be certain it is acidic, and then extract it sequentially with two 15-mL portions of diethyl ether to remove any unreacted nitrobenzene. Transfer the aqueous layer to an Erlenmeyer flask. Cool the contents of the flask in an ice-water bath and make the aqueous solution basic by slowly adding a minimum vo ume of 12 Msodium hydroxide solution. Saturate the aqueous solution with solid sodium chloride, cool the mixture to room temperature, and transfer it to a dean separatory funnel. Extract the aqueous mixture sequentially with two 15-mL portions of diethyl ether, using the first portion to rinse the flask in which the neutralization was done. Separate the aqueous layer from the organic layer as thoroughly as possible each time. Dry the combined organic extracts over several spatula-tips full anhydrous sodium sulfate. Decant the dried solution into a round-bottom flask, and remove most of the diethyl ether by simple distillation. Alternatively,... 

Pure pyridine may be prepared from technical coal-tar pyridine in the following manner. The technical pyridine is first dried over solid sodium hydroxide, distilled through an efficient fractionating column, and the fraction, b.p. 114 116° collected. Four hundred ml. of the redistilled p)rridine are added to a reagent prepared by dissolving 340 g. of anhydrous zinc chloride in a mixture of 210 ml. of concentrated hydrochloric acid and 1 litre of absolute ethyl alcohol. A crystalline precipitate of an addition compound (probable composition 2C5H5N,ZnCl2,HCl ) separates and some heat is evolved. When cold, this is collected by suction filtration and washed with a little absolute ethyl alcohol. The yield is about 680 g. It is recrystaUised from absolute ethyl alcohol to a constant m.p. (151-8°). The base is liberated by the addition of excess of concentrated... 

The above simple experiments illustrate the more important properties of aliphatic acid chlorides. For characterisation, the general procedure is to hydrolyse the acid chloride by warming with dilute alkali solution, neutralise the resulting solution with dilute hydrochloric acid (phenol-phthalein), and evaporate to dryness on a water bath. The mixture of the sodium salt of the acid and sodium chloride thus obtained may be employed for the preparation of solid esters as detailed under Aliphatic Acids, Section 111,85. The anilide or p-toluidide may be prepared directly from the acid chloride (see (iii) above and Section III,85,i). 

Benzoates. Dissolve 0-5 g. of the amino acid in 10 ml. of 10 per cent, sodium bicarbonate solution and add 1 g. of benzoyl chloride. Shake the mixture vigorously in a stoppered test-tube remove the stopper from time to time since carbon dioxide is evolved. When the odour of benzoyl chloride has disappeared, acidify with dilute hydrochloric acid to Congo red and filter. Extract the solid with a little cold ether to remove any benzoic acid which may be present. RecrystaUise the benzoyl derivative which remains from hot water or from dilute alcohol. 

Method 1. Treat 2 0 g. of the mixture of amines with 40 ml. of 10 per cent, sodium hydroxide solution and add 4 g. (3 ml.) of benzenesulphonyl chloi de (or 4 g. of p-toluenesulphonyl chloride) in small portions. Warm on a water bath to complete the reaction. Acidify the alkaline solution with dilute hydrochloric acid when the sulphonamides of the primary and secondary amines are precipitated. Filter off the solid and wash it with a little cold water the tertiary amine will be present in the filtrate. To convert any disulphOnamide that may have been formed from the primary amine into the sulphonamide, boil the solid under reflux with 2 0 g. of sodium dissolved in 40 ml. of absolute ethyl alcohol for 30 minutes. Dilute with a little water and distil off the alcohol filter off the precipitate of the sulphonamide of the secondary amine. Acidify the filtrate with dilute hydrochloric acid to precipitate the derivative of the primary amine. Recrystallise the respective derivatives from alcohol or from dilute alcohol, and identify them inter alia by a determination of the m.p. 

Method 2. Place a 3 0 g. sample of the mixture of amines in a flask, add 6g. (4-5 ml.) of benzenesulphonyl chloride (or 6 g. of p-toluenesulphonyl chloride) and 100 ml. of a 5 per cent, solution of sodium hydroxide. Stopper the flask and shake vigorously until the odour of the acid chloride has disappeared open the flask occasionally to release the pressure developed by the heat of the reaction. AUow the mixture to cool, and dissolve any insoluble material in 60-75 ml. of ether. If a solid insoluble in both the aqueous and ether layer appears at this point (it is probably the sparingly soluble salt of a primary amine, e.g., a long chain compound of the type CjH5(CH2) NHj), add 25 ml. of water and shake if it does not dissolve, filter it off. Separate the ether and aqueous layers. The ether layer will contain the unchanged tertiary amine and the sulphonamide of the secondary amine. Acidify the alkaline aqueous layer with dilute hydrochloric acid, filter off the sulphonamide of the primary amine, and recrystaUise it from dilute alcohol. Extract the ether layer with sufficient 5 per cent, hydrochloric acid to remove all the tertiary amine present. Evaporate the ether to obtain the sulphonamide of the secondary amine recrystaUise it from alcohol or dilute alcohol. FinaUy, render the hydrochloric acid extract alkaline by the addition of dilute sodium hydroxide solution, and isolate the tertiary amine. 

A solution of 1-piperazino ethyl acetate (Q2 mol) in benzene (300 ml) is treated with 3,4.5-trimethoxy cinnamoyl chloride (0,2 mol) in the presence of sodium bicarbonate (0.3 mol). After contacting for one hour at room temperature, the mixture is refluxed for a further hour. The benzene solution is then treated with an aqueous solution of sodium bicarbonate. After evaporation of the solvent, a solid product is obtained which is recrystallized from isopropyl ether. Melting point = 96°C. This base, when treated with hydrochloric acid, gives a hydrochloride having a melting point of 200°C with decomposition. By the action of malaic acid the acid maleate is obtained, having a melting point of 130°C. 

The following description is taken from U.S. Patent 3,116,203. A stirred solution of 75 g of 2-amino.2 -nitrobenzophenone in 700 ml of hot concentrated hydrochloric acid was cooled to 0°C and a solution of 21.5 g of sodium nitrite in 50 ml of water was added in the course of 3 hours. The temperature of the suspension was kept at 2° to 7°C during the addition. The resulting clear solution was poured into a stirred solution of 37 g of cuprous chloride in 350 ml of hydrochloric acid 1 1. The solid which had formed after a few minutes was filtered off, washed with water and recrystallized from ethanol. Crystals of 2-chloro-2 -nitrobenzophenone melting at 76° to 79°C were obtained. 

The organic fractions are combined and washed successively with N,N-dimethyl-1,3-propane-diamine, dilute hydrochloric acid, saturated sodium bicarbonate solution and saturated sodium chloride solution. The organic fraction is dried over anhydrous magnesium sulfate. The solvent is then evaporated off. Upon trituration of the residue with methanol, a solid crystallizes, 5-(p-toluovl)-1 -methvlpvrrole-2-acetonitrile, which is removed by filtration and purified by recrystallization from benzene. 

The resulting solution is poured into ice acidified with dilute hydrochloric acid. A white solid precipitates which Is extracted into ether. The ether phase is washed with a saturated solution of sodium chloride and dried over anhydrous magnesium sulfate. The solvent is evaporated and a white solid, 5-(p-toluoyl)-1 -methylpvrrole-2-acetic acid is obtained which is recrystal-lized twice from isopropanol, melting point 155°C to 157°C. 

A suspension of 30 g of sodium hydride in benzene (30 ml) was added dropwise to 52 g of 8-chlorodibenzo[b,f] thiepin-10(11 H)-one dissolved in dimethylformamide (800 ml), and the mixture was heated at 100°C for 2 hours. To this, there were added 68 g of 2-dimethylamino-ethyl chloride, and the mixture was heated at 60°C for 39 hours. The reaction mixture, after cooled, was poured into ice-water, and the solution was extracted with ethyl acetate. The ethyl acetate layer, after washed with water, was extracted with 10% hydrochloric acid, when oil was precipitated. The aqueous layer, in which oil was precipitated, was washed with ether, made neutral with concentrated sodium hydroxide solution and then extracted with ethyl acetate. The ethyl acetate layer was washed with water, dried over magnesium sulfate, and concentrated to give oil, which was allowed to stand to provide solid. The solid was washed with petroleum ether and recrystallized from cyclohexane to yield 42.5 g of 8melting point 90°C to 91°C. Male-ate as colorless needle, melting point 204°C to 204.5°C. 

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