Aniline extraction

Stipanovic, R. D., Donovan, J. C., Bell, A. A., and Martin, F. W. (1984). Factors interfering in gossypol analysis of okra and glandless cottonseed using direct aniline extraction. J. Agric. Food Chem. 32, 809-810. 

Dilute 1 c.c. of this aniline solution with 10 c.c. of water, and add a small quantity of a filtered water solution of bleaching powder. A violet colouration takes place by this reaction (Runge s), the most minute quantity of free aniline may be detected. If in this experiment the solution should not remain clear, but a dirty violet precipitate separate out, a too concentrated solution has been used the aniline water is diluted further, and the experiment repeated. If a salt of aniline is to be tested, it is dissolved in water, treated with alkali, the free aniline extracted with ether, this latter evaporated, and the residue dissolved in water. Then proceed exactly as just directed. 

K103. . Process residues from aniline extraction from the production of aniline... 

Acids also dissolve basic organic compounds such as amines and aniline. Extraction with acids should be avoided if cyanides or sulfides are present to prevent formation... 

Add 4 g. of aniline hydrochloride to 16 ml. of aniline contained in a 100 ml. conical flask, and then add 8 g. of diazoaminobenzene, both the solid components being finely powdered. Place the flask in a water-bath, and heat the latter carefully so that the well-stirred mixture is kept at 40° for i hour. Then remove the flask from the water-bath and allow it to stand overnight to ensure that the conversion is complete. Then add about 20 ml. of glacial acetic acid dissolved in the same volume of water, and stir the mixture well to extract the free aniline in the form of its soluble acetate. Allow the mixture to stand (with occasional stirring) for at least 10 minutes, and then filter at the... 

The mixed amines are dissolved in hydrochloric acid and zinc chloride solution added. The quinoline chlorozincate, (C H7N)2,HtZnCl, crystallises out, being almost insoluble in water, while the aniline chlorozincate remains in solution. The quinoline chlorozincate is then filtered off and decomposed by alkalis, and the liberated quinoline extracted with ether or steam-distilled. 

Dilute hydrochloric or sulphuric acid finds application in the extraction of basic substances from mixtures or in the removal of basic impurities. The dilute acid converts the base e.g., ammonia, amines, etc.) into a water-soluble salt e.g., ammonium chloride, amine hydrochloride). Thus traces of aniline may be separated from impure acetanilide by shaking with dilute hydrochloric acid the aniline is converted into the soluble salt (aniline hydrochloride) whilst the acetanilide remains unaffected. 

If the presence of unreduced nitrobenzene is suspected (odour and/or high b.p. residue), treat all the product with excess of dilute hydrochloric acid and remove the nitrobenzene either by steam distillation or by ether extraction render the residue alkaline with sodium hydroxide solution and isolate the aniline os before. 

Note on the laboratory preparation of monoethylaniline. Although the laboratory preparation of monomethyl- or monoethyl-aniline is hardly worth whUe, the following experimental details may be useful to those who wish to prepare pure monoethylaniline directly from amline. In a flask, fitted with a double surface reflux condenser, place 50 g. (49 ml.) of aniline and 65 g. of ethyl bromide, and boU gently for 2 hours or until the mixture has almost entirely sohdified. Dissolve it in water and boil off the small quantity of unreacted ethyl bromide. Render the mixture alkaUne with concentrated sodium hydroxide solution, extract the precipitated bases with three 50 ml. portions of ether, and distil off the ether. The residual oil contains anihne, mono- and di-ethylaniline. Dissolve it in excess of dilute hydrochloric acid (say, 100 ml. of concentrated acid and 400 ml. of water), cool in ice, and add with stirring a solution of 37 g. of sodium nitrite in 100 ml. of water do not allow the temperature to rise above 10°. Tnis leads to the formation of a solution of phenyl diazonium chloride, of N-nitrosoethylaniline and of p-nitrosodiethylaniline. The nitrosoethylaniline separates as a dark coloured oil. Extract the oil with ether, distil off the ether, and reduce the nitrosoamine with tin and hydrochloric acid (see above). The yield of ethylaniline is 20 g. 

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. 

Hydrolysis of benzanilide. Place 5 g. of benzanilide and 50 ml. of 70 per cent, sulphuric acid in a small flask fitted with a reflux condenser, and boU gently for 30 minutes. Some of the benzoio acid will vapourise in the steam and solidify in the condenser. Pour 60 ml. of hot water down the condenser this will dislodge and partially dissolve the benzoic acid. Cool the flask in ice water filter off the benzoic acid (anifine sulphate does not separate at this dilution), wash well with water, drain, dry upon filter paper, and identify by m.p. (121°) and other tests. Render the filtrate alkaline by cautiously adding 10 per cent, sodium hydroxide solution, cool and isolate the aniline by ether extraction. Recover the ether and test the residue for anifine (Section IV,100). 

Method 2. Suspend 2-0 g. of methyl orange in 4 ml. of water, and add a small quantity of sodium hyposulphite (Na2S204). Heat the mixture and add more sodium hyposulphite until the colour is discharged. The sulphanilic acid remains in the solution as sodium sulphanilate and the p-aminodimethyl-aniline may be extracted with ether as in Method 1. 

Equip a 500 ml. three-necked flask with a powerful mechanical stirrer and a separatory funnel leave the third neck open or loosely stoppered. Introduce, while the flask is cooled in a freezing mixture of ice and salt, 90 ml. of concentrated ammonia solution (sp. gr. 0 -88) and 54 g. (43 ml.) of pure (e.g., A.R.) carbon disulphide. Stir the mixture and run in 56 g. (55ml.)of pure aniline from the separatory funnel during about 20minutes stir for a further 30 minutes, and allow to stand for another 30 minutes. A heavy precipitate of ammonium phenyldithiocarbamate separates. Transfer the salt to a 5 litre round-bottomed flask by four extractions with 200 ml. portions of water. Add to the resulting solution, with... 

Into a 1-litre beaker, provided with a mechanical stirrer, place 36 - 8 g. (36 ml.) of aniline, 50 g. of sodium bicarbonate and 350 ml. of water cool to 12-15° by the addition of a little crushed ice. Stir the mixture, and introduce 85 g. of powdered, resublimed iodine in portions of 5-6 g, at intervals of 2-3 minutes so that all the iodine is added during 30 minutes. Continue stirring for 20-30 minutes, by which time the colour of the free iodine in the solution has practically disappeared and the reaction is complete. Filter the crude p-iodoaniline with suction on a Buchner funnel, drain as completely as possible, and dry it in the air. Save the filtrate for the recovery of the iodine (1). Place the crude product in a 750 ml. round-bottomed flask fitted with a reflux double surface condenser add 325 ml. of light petroleum, b.p. 60-80°, and heat in a water bath maintained at 75-80°. Shake the flask frequently and after about 15 minutes, slowly decant the clear hot solution into a beaker set in a freezing mixture of ice and salt, and stir constantly. The p-iodoaniline crystallises almost immediately in almost colourless needles filter and dry the crystals in the air. Return the filtrate to the flask for use in a second extraction as before (2). The yield of p-iodoaniline, m.p. 62-63°, is 60 g. 

Separations based upon differences in the chemical properties of the components. Thus a mixture of toluene and anihne may be separated by extraction with dilute hydrochloric acid the aniline passes into the aqueous layer in the form of the salt, anihne hydrochloride, and may be recovered by neutralisation. Similarly, a mixture of phenol and toluene may be separated by treatment with dilute sodium hydroxide. The above examples are, of comse, simple apphcations of the fact that the various components fah into different solubihty groups (compare Section XI,5). Another example is the separation of a mixture of di-n-butyl ether and chlorobenzene concentrated sulphuric acid dissolves only the w-butyl other and it may be recovered from solution by dilution with water. With some classes of compounds, e.g., unsaturated compounds, concentrated sulphuric acid leads to polymerisation, sulphona-tion, etc., so that the original component cannot be recovered unchanged this solvent, therefore, possesses hmited apphcation. Phenols may be separated from acids (for example, o-cresol from benzoic acid) by a dilute solution of sodium bicarbonate the weakly acidic phenols (and also enols) are not converted into salts by this reagent and may be removed by ether extraction or by other means the acids pass into solution as the sodium salts and may be recovered after acidification. Aldehydes, e.g., benzaldehyde, may be separated from liquid hydrocarbons and other neutral, water-insoluble hquid compounds by shaking with a solution of sodium bisulphite the aldehyde forms a sohd bisulphite compound, which may be filtered off and decomposed with dilute acid or with sodium bicarbonate solution in order to recover the aldehyde. 

Even though they are weaker bases arylammes like alkylammes can be com pletely protonated by strong acids Aniline is extracted from an ether solution into 1 M hydrochloric acid by being completely converted to a water soluble amlimum salt under these conditions... 

The older methods have been replaced by methods which require less, if any, excess sulfuric acid. For example, sulfonation of naphthalene can be carried out in tetrachloroethane solution with the stoichiometric amount of sulfur trioxide at no greater than 30°C, followed by separation of the precipitated l-naphthalenesulfonic acid the filtrate can be reused as the solvent for the next batch (14). The purification of 1-naphthalenesulfonic acid by extraction or washing the cake with 2,6-dimethyl-4-heptanone (diisobutyl ketone) or a C-1—4 alcohol has been described (15,16). The selective insoluble salt formation of 1-naphthalenesulfonic acid in the sulfonation mixture with 2,3-dimethyl aniline has been patented (17). 

After leaving the reactor, the reaction mixture consisting of aniline, water, and excess hydrogen is cooled and condensed prior to the purification steps. First, the excess hydrogen is removed and recycled back to the reactor. The rest of the mixture is sent to the decanter where the water and aniline are separated. The cmde aniline, which contains less than 0.5% of unreacted nitrobenzene and about 5% water, is distilled in the cmde aniline column. The aniline is further dehydrated in the finishing column to yield the purified aniline. Meanwhile, the aqueous layer from the decanter, which contains about 3.5% aniline, is extracted to recover the aniline and clean up the water before it is sent to the waste-water treatment plant. 

Phenethylanillne 1 (hydrochloride) (23 3 g 01 mol) was heated in a sealed tube at 200 230 Clor6h The cooled mixture was extracted with 15% HCI and Et20 The Et20 layer was extracted with HCI The acid extract alter neutralization with S% NaOH, extraction with PhH and distillation gave 2 3 g of aniline and 4 2 g of 2 and 3 (24%), bp 165 170°C m a ratio of 3 7... 

Aniline will be used as a second example. It has a pK of 4.60 at 25° in H2O. If it is placed in aqueous solution at pH 1.60 it will exist almost completely (99.9%) as the anilinium cation. This solution can then be extracted with solvents e.g. diethyl ether to remove neutral impurities. The pH of the solution is then adjusted to 7.60 whereby aniline will exist as the free base (99.9%) and can be extracted into diethyl ether in order to give purer aniline. 

---