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50 grms. m-dinitrobenzene. 150

alcohol (90 per cent.). 25

conc. ammonia.

Fifty grms. dinitrobenzene, 150 grms, dilute alcohol (90 per cent.), and 25 grms. conc. ammonia are mixed together in a half-litre flask, and into the dark red pasty mass sulphuretted hydrogen is passed, the mixture being well stirred meanwhile.* The dinitrobenzene slowly dissolves, and when the red liquid is saturated with the gas, crystalline flakes of ammonium thiosulphate begin to separate. When the solution is completely saturated, it is heated on the water-bath until any excess of sulphuretted hydrogen is expelled; at the same time sulphur separates out in quantity. After cooling, the liquid is again saturated with sulphuretted hydrogen as before, and heated on the water-bath, and the same process repeated until the contents of the flask have increased in weight about 30 grms. A sufficient quantity of water is now added to the liquid to precipitate the nitraniline and filtered.

In order to purify the crude product, it is repeatedly extracted with small quantities of dilute hydrochloric acid, the acid solution somewhat concentrated, whereby a small quantity of unchanged dinitrobenzene separates, and filtered. Conc. ammonia added to the filtrate precipitates the m-nitraniline, which may be purified by recrystallisation from boiling water. The filtrate from the crude nitraniline is acidified with dilute hydrochloric acid, and evaporated to dryness on the water bath. The residue is extracted with dilute hydrochloric acid, and the filtered solution treated with conc. ammonia. In this way a further quantity of nitraniline may be obtained. C.4,(N0g)2 + 3NH,HS = CH.NA: + 3NH2 + 35 + 311,0

[blocks in formation]

Properties.--Yellow needles; m. p. 114°; b. p. 285°. Compare the melting point with that of ortho- and para-nitraniline, p. 28.

PREPARATION IX.

,

C,H,

s C

1 C2H5. LITERATURE.-A. W. Hofmann (1850), Ann. Ch, Pharm. 74, 128.

50 grms. aniline.
65

ethyl bromide.

A. mixture of 50 grms. pure commercial aniline and 65 grms, ethyl bromide are heated on the waterbath in a flask connected with reflux condenser. After about three hours the contents of the flask have solidified to a brownish crystalline mass consisting of the mixed hydrobromides of diethyl-, monoethylaniline and aniline. Water is added, which readily dissolves the hydrobromides, and then excess of caustic potash solution. The free bases separate out as a dark brown oily layer on the surface of the liquid. The aqueous portion is carefully separated and extracted with ether, the ether distilled, and the residue added to the other oil. The whole is mixed with an equal weight of acetic anhydride, which causes a considerable rise of temperature and converts the aniline and monoethylaniline into the corresponding acetyl compounds, whereas the diethyl compound is unacted upon. The mixture is distilled in a retort connected with a condenser and receiver. At first excess of acetic anhydride and some acetic acid pass over. The thermometer then rises rapidly and the portion distilling above 180° is collected in a separate vessel. At this point it is advisable to run the water out of the condenser to avoid cracking the tube or to replace the condenser simply by a straight wide tube. A portion of the distillate, on cooling, solidifies to a yellow crystalline mass. The oil is drained off by filtering with the pump through a platinum cone and the residue is washed with small quantities of cold and very dilute sulphuric acid. The filtrate contains the diethylaniline. The crystalline residue consists of the acetyl compounds

of aniline and monoethylaniline.1 The filtrate is made alkaline with caustic potash solution extracted with ether and dehydrated over solid caustic potash. The ether is distilled off on the water-bath and the residual oil fractionated over the flame. The light yellow oil passing over at 210°—215° is nearly pure diethylaniline. CH5NH, + 2C,H,Br = C,H,N(C2H3)2 + 2HBr

Diethylaniline. Properties.--Colourless oil; b. p. 213-5°; sp. gr. *936 at 18°.

PREPARATION X.

PARA-NITROSODIMETHYLANILINE,

C3H2N,0 = Co H,{I}N(CH3'2

4(4)NO. LITERATURE.-Baeyer, Caro (1874), Ber. 7, 810 and 963 ; Schraube (1875), Ber. 8, 616; Wurster (1879), Ber. 12, 523.

1 The monoethylaniline may be isolated by boiling the mixed acetyl compounds with slight excess of 20 per cent. hydrochloric acid for two hours, adding excess of caustic potash solution and distilling with steam. The mixture of oil and water in the receiver is acidified with dilute sulphuric acid, and a small quantity of sodium nitrite solution slowly added to the cold solution. The aniline is converted into diazobenzene sulphate, which dissolves; the ethyl aniline into ethylphenylnitrosamine, which separates as an oil and may be extracted with ether. After distilling off the ether the nitrosamine is reduced with tin and hydrochloric acid, and is reconverted into monoethylaniline (Fischer).

D

50 grms. dimethylaniline.
125 conc. hydrochloric acid diluted

with 250 grms. water.
30

sodium nitrite. To a solution of 50 grms. dimethylaniline in 125 grms. conc. hydrochloric acid diluted with 250 grms. water, rather more than the calculated quantity of sodium nitrite (30 grms.) dissolved in a small quantity of water is slowly added and the mixture well shaken and cooled in ice. The separation of the hydrochloride of nitrosodimethylaniline in the form of small yellow needles soon begins, and the liquid is gradually filled with a thick crystalline deposit. When after standing for some time no further increase in the quantity of crystals is observed, the mass is filtered at the pump and washed with alcohol containing hydrochloric acid. The salt may be purified by recrystallisation from hot water. It forms small yellow needles. In order to prepare the free base, the hydrochloride is mixed into a paste with water and excess of potassium carbonate or caustic soda solution added in the cold. The yellow colour of the salt changes to green and the free base, which is formed, is extracted with ether. On evaporating off the ether the base remains in the form of brilliant green foliated crystals. C&H N(CH3),HCl + HNO, = C H (NO)N(CH3)2. HCI+H.,O Dimethylaniline

p-Nitrosodimethylaniline hydrochloride

hydrochloride.

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