Concentrated Hydrochloric Acid Cuprous

Meanwhile, during the cooling of the cuprous chloride solution, prepare a solution of benzenediazonium chloride by dissolving 20 ml. (20-5 g.) of aniline in a mixture of 50 ml. of concentrated hydrochloric acid and 50 ml. of water, and after cooling to 5°, adding slowly a solution of 17 g. of sodium nitrite in 40 ml. of water. Observe carefully the general conditions for diazotisation given in the preparation of iodobenzene (p. 184). 

Allyl Chloride. Comparatively poor yields are obtained by the zinc chloride - hydrochloric acid method, but the following procedure, which employs cuprous chloride as a catalyst, gives a yield of over 90 per cent. Place 100 ml. of allyl alcohol (Section 111,140), 150 ml. of concentrated hydrochloric acid and 2 g. of freshly prepared cuprous chloride (Section II,50,i one tenth scale) in a 750 ml. round-bottomed flask equipped with a reflux condenser. Cool the flask in ice and add 50 ml. of concen trated sulphuric acid dropwise through the condenser with frequent shaking of the flask. A little hydrogen chloride may be evolved towards the end of the reaction. Allow the turbid liquid to stand for 30 minutes in order to complete the separation of the allyl chloride. Remove the upper layer, wash it with twice its volume of water, and dry over anhydrous calcium chloride. Distil the allyl chloride passes over at 46-47°. 

In a 1 5 or 2-Utre rovmd-bottomed flask, prepare cuprous chloride from 105 g. of crystallised copper sulphate as detailed in Section 11,50,1. Either wash the precipitate once by decantation or filter it at the pump and wash it with water containing a httle sulphurous acid dissolve it in 170 ml. of concentrated hydrochloric acid. Stopper the flask loosely (to prevent oxidation) and cool it in an ice - salt mixture whilst the diazo-tisation is being carried out. 

Chlorobenzene. Prepare a solution of phenyldiazonium chloride from 31 g. (30 -5 ml.) of aniUne, 85 ml. of concentrated hydrochloric acid, 85 ml, of water, and a solution of 24 g. of sodium nitrite in 50 ml. of water (for experimental details, see Section IV,60). Prepare cuprous chloride from 105 g. of crystallised copper sulphate (Section 11,50,1), and dissolve it in 170 ml. of concentrated hydrochloric acid. Add the cold phenyl diazonium chloride solution with shaking or stirring to the cold cuprous chloride solution allow the mixture to warm up to room temperature. Follow the experimental details given above for p-chlorotoluene. Wash the chlorobenzene separated from the steam distillate with 40 ml. of 10 per cent, sodium hydroxide solution (to remove phenol), then with water, dry with anhydrous calcium chloride or magnesium sulphate, and distil. Collect the chlorobenzene (a colourless liquid) at 131-133° (mainly 133°), The yield is 29 g. 

The amine (Imol) is added to a solution of anhydrous zinc chloride (Imol) in concentrated hydrochloric acid (42mL) in ethanol (200mL, or less depending on the solubility of the double salt). The solution is stirred for Ih and the precipitated salt is filtered off and recrystallised from ethanol. The free base is recovered by adding excess of 5-ION NaOH (to dissolve the zinc hydroxide that separates) and is steam distilled. Mercuric chloride in hot water can be used instead of zinc chloride and the salt is crystallised from 1% hydrochloric acid. Other double salts have been used, e.g. cuprous salts, but are not as convenient as the above salts. 

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. 

While the cuprous cyanide solution is warmed gently (to 60°-70°) on the water bath, a solution of p-tolyldiazonium chloride is prepared as follows Heat 20 g. of p-toluidine with a mixture of 50 g. of concentrated hydrochloric acid and 150 c.c. of water until dissolution is complete. Immerse the solution in ice-water and stir vigorously with a glass rod so that the toluidine hydrochloride separates as far as possible in a microcrystalline form. Then cool the mixture in ice and diazotise with a solution of 16 g. of sodium nitrite in 80 c.c. of water, added until the nitrous acid test with potassium iodide-starch paper persists. The diazonium chloride solution so obtained is poured during the course of about ten minutes into the warm cuprous cyanide solution, which is meanwhile shaken frequently. After the diazo-solution has been added the reaction mixture is heated under an air condenser on the water bath fox a further quarter of an hour, and then the toluic nitrile is separated by distillation with steam (fume chamber, HCN ). The nitrile (which passes over as a yellowish oil) is extracted from the distillate with ether, the p-cresol produced as a by-product is removed by shaking the ethereal extract twice with 2 A-sodium hydroxide solution, the ether is evaporated,... 

To a solution of 1200 g. of copper sulfate and 400 g. of sodium chloride in 4 1. of water at 60-70° is added a concentrated solution of 200 g. of (90-95 per cent) sodium bisulfite (prepared if desired by saturating with sulfur dioxide a solution of 100 g. of sodium carbonate). The white precipitate of cuprous chloride is filtered off, sucked dry as rapidly as possible, and suspended in a mixture of 2 1. of water and 1500 cc. of concentrated hydrochloric acid (Note 1). 

To a flask equipped with a stirrer and condenser is added 37.2 gm (0.5 mole) of 3-chloropropyne, 5.0 gm (0.051 mole) of cuprous chloride, 4.0 gm (0.075 mole) of ammonium chloride, 4.0 ml of concentrated hydrochloric acid, and... 

To a large bottle are added 116.5 gm (1.0 mole) of 3-chloro-l-hexyne, 20.0 gm (0.20 mole) of cuprous chloride, 16.0 gm (0.30 mole) of ammonium chloride, 10 ml of concentrated hydrochloric acid, 50 ml of water, and 0.6 gm of copper bronze. The bottle is sealed and shaken at room temperature for 14 days. The organic layer is separated, dried over potassium carbonate, and fractionally distilled through a glass-helix-packed column to afford 61.0 gm (52%) of nearly pure l-chloro-l,2-hexadiene, b.p. 54°-57°C (50 mm), p5 1.4567-1.4680, 9.3 gm (8%) of 3-chloro-l-hexyne, and some polymeric material. Shorter periods of reaction give lower yields. The product is purified as described for bromopropadiene. 

To a flask equipped with two dropping funnels and containing 2 liters of saturated sodium chloride solution, 50.0 gm (0.51 mole) of cuprous chloride, 2.0 gm of copper powder, and 50 ml of concentrated hydrochloric acid warmed to 75°C is added a 30% sodium cyanide solution until the pH approaches approximately 3-4. At this time 150.0 gm (2.0 mole) of propargyl chloride is added dropwise over a 4-hr period. At the same time, more of the aqueous 30 % sodium cyanide is added to keep the pH constant at 3-4. The reaction product is later steam-distilled from the catalyst solution, separated from the water, dried, and fractionally distilled to afford 96.0 gm (73 %), b.p. 60°-67°C (95 mm), n ° 1.44-1.45. This product is contaminated with propargyl cyanide and is refractionated to afford pure cyanoallene, b.p. 50°-51.5°C (50 mm), d° 1.4612, Amax 46,500 cm 1, emax 14,200 (methanol). 

Method 3-4 is an improvement over the method of making bromopropadiene by shaking 3-bromopropyne for 6 days with cuprous bromide, concentrated hydrochloric acid, ammonium bromide, and copper bronze to afford a 28 % yield of bromopropadiene. 

Secondary and tertiary chlorides can be rearranged to allenes with the aid of concentrated hydrochloric acid in the presence of cuprous chloride and ammonium chloride [57]. 

Alternative Method.—Cupric chloride would serve better than a mixture of salt and copper sulfate, but it is much more expensive. A still simpler way is to start with copper. Place a suitable quantity in a flask and add concentrated hydrochloric acid in the ratio given in the last exercise. Heat nearly to boiling and add concentrated nitric acid drop by drop through a separatory funnel. When most of the copper has dissolved, stop adding nitric acid, heat vigorously for a time, and pour into cold water containing sodium sulfite. Proceed as in the first method. The aqua regia converts some of the copper into cupric chloride, and this is reduced to the cuprous salt by the excess of copper. 

Dissolve 20 g. of cuprous chloride, CuCl, in the least possible volume of concentrated hydrochloric acid. Cool the solution in ice and slowly add 500 cc. of concentrated ammonia. Keeping the temperature at 0°, add 55 g. of carbon disulfide and shake vigorously at frequent intervals. After standing some 6 days in an ice box at approximately 0°, shining green crystals of the thio-carbonate separate from the solution. Filter off these crystals, wash them with cold water, and quickly dry them on paper. The potassium salt can be made with slight modifications of these directions. 

As in the case of ferric chloride, cupric chloride is only incompletely reduced by sulphur dioxide in concentrated hydrochloric acid solution, but in aqueous solution this forms an excellent method for the preparation of cuprous chloride ... 

Experiment shows that cuprous chloride is oxidised in concentrated hydrochloric acid solution, thus ... 

Arsenic acid in solution is readily reduced by nascent hydrogen, arsine being evolved in the presence of alkali, however, this reduction does not take place.1 When distilled with concentrated hydrochloric acid, arsenic trichloride is formed and passes into the distillate the reaction is accelerated by the presence of organic matter 2 or other reducing agents, such as ferrous 3 or cuprous 4 salts. The reaction 5... 

When arsenic trisulphide is exposed to dry hydrogen chloride or hydrogen bromide, it liquefies at the ordinary temperature and on heating complete volatilisation occurs.9 It is not readily attacked by halogen acids. When boiled with concentrated hydrochloric acid it is decomposed, but with great difficulty, and the hydrogen sulphide and arsenious chloride evolved reproduce arsenious sulphide in the receiver.10 A similar reaction occurs when heated with a chloride in the presence of concentrated sulphuric acid, but the decomposition is incomplete.11 The reaction is facilitated by the presence of cuprous chloride or ferric chloride. Only a slight reaction is observed with dilute acid,12 and the... 

---