Potassium aniline

Mono-substituted and unsymmetrical di-substituted ureas may be prepared by a modification of Wohler s urea synthesis, salts of primary or secondary amines being used instead of the ammonium salt for interaction with potassium cyanate. Thus when an aqueous solution containing both aniline hydrochloride and potassium cyanate is heated, aniline cyanate is first formed, and then C,HjNH,HCl -h KCNO = C,H6NHj,HCNO -h KCl C,HsNH HCNO = C.H NHCONH, by the usual molecular rearrangement is converted into monophenyburea. 

Dissolve 5 g. of aniline hydrochloride in 120 ml. of hot water contained in a 200 ml. conical flask and then add 4 g. of potassium cyanate. Heat the solution on a water-bath for 30 minutes, adding about 1-2 g. of animal charcoal towards the end of the heating if a slight turbidity has developed. Now bring the solution quickly to the boil over a gauze, and filter it at the pump, using a Buchner funnel and flask which have been preheated by the filtration of some boiling distilled water. The clear... 

Required Aniline, 15 ml. hydrochloric acid, 40 ml. sodium nitrite, 12-5 g. potassium iodide, 35 g. 

Required Aniline, 20 ml. hydrochloric acid, 50 ml. sodium nitrite, 17 g. copper sulphate, 55 g. potassium cyanide, 60 g. 

Required Sulphuric acid, 27-5 ml. aniline, 24 ml. sodium nitrite, 20 g. dry potassium carbonate, 3-4 g. (To ensure that the potassium carbonate is dry, it should be gently heated in an evaporating-basin over a small Bunsen flame for 4-5 minutes with stirring, and then allowed to cool in a desiccator.)... 

Required Aniline, 30 ml. onrhlorobenzoic acid, 8 g. potassium carbonate, 8 g. powdered copper oxide, 0 4 g. 

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°. 

Calcium chloride cannot be used to dry the ethereal solution because it combines with aniline (and other amines) to form molecular compounds. The best drying agent is sodium or potassium hydroxide (pellet form). 

The experimental details for mono-M-propylanillne are as follows. Reflux a mixture of 230 g. of aniline and 123 g. of n-propyl bromide for 8-10 hours. Allow to cool, render the mixture alkafine, and add a solution of 150 g. of zinc chloride in 150 g. of water. Cool the mixture and stir after 12 hours, filter at the pump and drain well. Extract the thick paste several times with boiling light petroleum, b.p. 60-80° (it is best to use a Soxhlet apparatus), wash the combined extracts successively with water and dilute ammonia solution, and then dry over anhydrous potassium carbonate or anhydrous magnesium sulphate. Remove the solvent on a water bath, and distil the residue from a Claisen flask with fractionating side arm (well lagged). Collect the n-propyl-aniline at 218-220° the yield is 80 g. Treat the pasty solid zincichloride with an excess of. sodium hydroxide solution and steam distil 130 g. of pure aniline are recovered. 

Place 130 ml. of concentrated hj drochloric acid in a 1 - 5 litre round-bottomed flask, equipped ith a mechanical stirrer and immersed in a freezing mixture of ice and salt. Start the stirrer and, when the temperature has fallen to about 0°, add 60 g. of finely-crushed ice (1), run in 47 5 g. (46 5 ml.) of pure aniline during about 5 minutes, and then add another 60 g. of crushed ice. Dissolve 35 g. of sodium nitrite in 75 ml. of water, cool to 0-3°, and run in the cold solution from a separatory funnel, the stem of which reaches nearly to the bottom of the flask. During the addition of the nitrite solution (ca. 20 minutes), stir vigorously and keep the temperature as near 0° as possible by the frequent addition of crushed ice. There should be a slight excess of nitrous acid (potassium iodide-starch paper test) at the end of 10 minutes after the last portion of nitrite is added. 

An alternative method of removing the aniline is to add 30 ml. of concentrated sulphuric acid carefully to the steam distillate, cool the solution to 0-5°, and add a concentrated solution of sodium nitrite until a drop of the reaction mixture colours potassium iodide - starch paper a deep blue instantly. As the diazotisation approaches completion, the reaction becomes slow it will therefore be necessary to teat for excess of nitrous acid after an interval of 5 minutes, stirring all the whUe. About 12 g. of sodium nitrite are usually required. The diazotised solution is then heated on a boiling water bath for an hour (or until active evolution of nitrogen ceases), treated with a solution of 60 g. of sodium hydroxide in 200 ml. of water, the mixture steam-distilled, and the quinoline isolated from the distillate by extrsM-tion with ether as above. 

N-Phenylanthranilic acid may be prepared by the action of aniline upon c-chlorobenzoic acid in the presence of anhydrous potassium carbonate and a little copper oxide ... 

In a 1 litre round-bottomed flask, equipped with an air condenser, place a mixture of 44 g. of o-chlorobenzoic acid (Section IV,157) (1), 156 g. (153 ml.) of redistilled aniline, 41 g. of anhydrous potassium carbonate and 1 g. of cupric oxide. Reflux the mixture in an oil bath for 2 hours. Allow to cool. Remove the excess of aniline by steam distillation and add 20 g. of decolourising carbon to the brown residual solution. Boil the mixture for 15 minutes, and filter at the pump. Add the filtrate with stirring to a mixture of 30 ml. of concentrated hydrochloric acid and 60 ml. of water, and allow to cool. Filter off the precipitated acid with suction, and dry to constant weight upon filter paper in the air. The yield of iV-phenylanthranilic acid, m.p. 181-182° (capillary tube placed in preheated bath at 170°), is 50 g. This acid is pure enough for most purposes. It may be recrystaUised as follows dissolve 5 g. of the acid in either 25 ml. of alcohol or in 10 ml. of acetic acid, and add 5 ml. of hot water m.p. 182-183°. 

Formic acid is a good reducing agent in the presence of Pd on carbon as a catalyst. Aromatic nitro compounds are reduced to aniline with formic acid[100]. Selective reduction of one nitro group in 2,4-dinitrotoluene (112) with triethylammonium formate is possible[101]. o-Nitroacetophenone (113) is first reduced to o-aminoacetophenone, then to o-ethylaniline when an excess of formate is used[102]. Ammonium and potassium formate are also used for the reduction of aliphatic and aromatic nitro compounds. Pd on carbon is a good catalyst[103,104]. NaBH4 is also used for the Pd-catalyzed reduction of nitro compounds 105]. However, the ,/)-unsaturated nitroalkene 114 is partially reduced to the oxime 115 with ammonium formate[106]... 

Other Compounds. Primary and secondary amines add 1,4- to isoprene (75). For example, dimetbylamine in ben2ene reacts with isoprene in the presence of sodium or potassium to form dimetby1(3-metby1-2-buteny1)amine. Similar results are obtained with diethylamine, pyrroHdine, and piperidine. Under the same conditions, aniline and /V-metbylaniline do not react. Isoprene reacts with phenol in the presence of aluminum phenoxide (76) or concentrated phosphoric acid (77) to give complex products. 

In the known absence of bromoform, iodoform, chloral, and other halogenated methanes, the formation of phenyhsonitrile with aniline provides a simple and faidy sensitive but nonspecific test for the presence of chloroform, the carbylamine test. Phenyhsonitrile formation is the identification test given in the British Pharmacopoeia. A small quantity of resorcinol and caustic soda solution (10% concentration) added to chloroform results in the appearance of a yellowish red color, fluorescing yeUow-green. When 0.5 mL of a 5% thymol solution is boiled with a drop of chloroform and a small quantity of potassium hydroxide solution, a yellow color with a reddish sheen develops the addition of sulfuric acid causes a change to brilliant violet, which, diluted with water, finally changes to blue (33). 

Oxidation of phenols or anilines to quinones by means of potassium nitrosodlsuHanate (Fremy s salt). 

Diaminoazobenzene was reported by Nietzki to have been prepared by diazotizing -nitroaniline and coupling the product with aniline. The resulting 4-nitrodiazoaminobenzene is rearranged and the nitro group reduced. The submitters tried several times to carry out this procedure but were unsuccessful. 4,4 -Diaminoazobenzene has been prepared by the oxidation of -nitroaniline with potassium persulfate followed by the reduction of the nitro groups. ... 

An early ease in whieh the existenee of benzyne as a reaetion intermediate was established was in the reaction of chlorobenzene with potassium amide. Carbon-14 label in the starting material was found to be distributed in the aniline as expeeted for a benzyne intermediate. ... 

A solution to the question of the mechanism of these reactions was provided by John D. Roberts in 1953 on the basis of an imaginative experiment. Roberts prepared a sample of chlorobenzene in which one of the car bons, the one bearing the chlorine, was the radioactive mass-14 isotope of carbon. Reaction with potassium amide in liquid fflnmonia yielded aniline containing almost exactly half of its label at C-1 and half at C-2 ... 

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