Metanilic acid

In a 500 ml. bolt-head flask, provided with a mechanical stirrer, place 70 ml. of oleum (20 per cent. SO3) and heat it in an oil bath to 70°. By means of a separatory funnel, supported so that the stem is just above the surface of the acid, introduce 41 g. (34 ml.) of nitrobenzene slowly and at such a rate that the temperature of the well-stirred mixture does not rise above 100-105°. When all the nitrobenzene has been introduced, continue the heating at 110-115° for 30 minutes. Remove a test portion and add it to the excess of water. If the odour of nitrobenzene is still apparent, add a further 10 ml. of fuming sulphuric acid, and heat at 110-115° for 15 minutes the reaction mixture should then be free from nitrobenzene. Allow the mixture to cool and pour it with good mechanical stirring on to 200 g. of finely-crushed ice contained in a beaker. AU the nitrobenzenesulphonic acid passes into solution if a little sulphone is present, remove this by filtration. Stir the solution mechanically and add 70 g. of sodium chloride in small portions the sodium salt of m-nitro-benzenesulphonic acid separates as a pasty mass. Continue the stirring for about 30 minutes, allow to stand overnight, filter and press the cake well. The latter will retain sufficient acid to render unnecessary the addition of acid in the subsequent reduction with iron. Spread upon filter paper to dry partially. 

Place 84 g. of iron filings and 340 ml. of water in a 1 - 5 or 2-litre bolt-head flask equipped with a mechanical stirrer. Heat the mixture to boiling, stir mechanically, and add the sodium m-nitrobenzenesulphonate in small portions during 1 hour. After each addition the mixture foams extensively a wet cloth should be applied to the neck of the flask if the mixture tends to froth over the sides. Replace from time to time the water which has evaporated so that the volume is approximately constant. When all the sodium salt has been introduced, boU the mixture for 20 minutes. Place a small drop of the suspension upon filter paper and observe the colour of the spot it should be a pale brown but not deep brown or deep yellow. If it is not appreciably coloured, add anhydrous sodium carbonate cautiously, stirring the mixture, until red litmus paper is turned blue and a test drop upon filter paper is not blackened by sodium sulphide solution. Filter at the pump and wash well with hot water. Concentrate the filtrate to about 200 ml., acidify with concentrated hydrochloric acid to Congo red, and allow to cool. Filter off the metanilic acid and dry upon filter paper. A further small quantity may be obtained by concentrating the mother liquid. The yield is 55 g. 

Primary aromatic amines differ from primary aliphatic amines in their reaction with nitrous acid. Whereas the latter yield the corresponding alcohols (RNHj — ROH) without formation of intermediate products see Section 111,123, test (i), primary aromatic amines 3neld diazonium salts. Thus aniline gives phcnyldiazonium chloride (sometimes termed benzene-diazonium chloride) CjHbNj- +C1 the exact mode of formation is not known, but a possible route is through the phenjdnitrosoammonium ion tlius  

Phenyldiazonium chloride and other similar diazonium compounds are very soluble in water, are completely insoluble in ether and other organic solvents, and are completely dissociated in aqueous solution to organic cations and inorganic anions (e.g., chloride ions) a convenient formulation is therefore, for example, CjHjNj+CP. 

The experimental conditions necessary for the preparation of a solution of a diazonium salt, diazotisation of a primary amine, are as follows. The amine is dissolved in a suitable volume of water containing 2 5-3 equivalents of hydrochloric acid (or of sulphuric acid) by the application of heat if necessary, and the solution is cooled in ice when the amine hydrochloride (or sulphate) usually crystallises. The temperature is maintained at 0-5°, an aqueous solution of sodium nitrite is added portion-wise until, after allowing 3-4 minutes for reaction, the solution gives an immediate positive test for excess of nitrous acid with an external indicator—moist potassium iodide - starch paper f  

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Other disazo dyes with good substantivity and high wet-fastness properties on polyamides are Acid Red 114 (40), made by coupling o-toHdine to phenol which is then coupled to G-acid, followed by reaction of the phenoHc hydroxyl group with -toluenesulfonyl chloride, and Acid Blue 113 (41) (metanilic acid — 1-naphthylamine — 8-anilino-1-naphthalenesulfonic acid). 

Its production was 621 t and the average price 0.75/kg in 1987. Direct YeUow 44 (64) is prepared by phosgenation of an equimolar mixture of metanilic acid coupled to o-anisidinomethanesulfonic acid (with subsequent hydrolysis of the methanesulfonic acid group) and nitro aniline coupled to sahcychc acid (with subsequent reduction of the nitro group). 

Direct Blue 218 had reported sales of 623 t valued at 4.4 million ia 1987. It is produced from Direct Blue 15 (76) by metallizing and elimination of methyl groups from the methoxide to form the copper complex. Direct Blue 15 (76) is prepared by coupling o-dianisidine [119-90-4] to two moles of H-acid (4-amiQO-5-hydroxy-2,7-naphthalenedisulfonic acid) under alkaline pH conditions. Other important direct blues iaclude Direct Blue 80 (74), (9-dianisidine coupled to two moles of R-acid (3-hydroxy-2,7-naphthalenedisulfonic acid [148-75-4]) followed by metallizing to form a bis copper complex, and Direct Blue 22 (77), an asymmetrical disazo dye, prepared by coupling o-dianisidine to Chicago acid [82-47-3] and 2-naphthol. Direct Blue 75 (78) is an example of a trisazo dye represented as metanilic acid — 1,6-Q.eve s acid — 1,6-Q.eve s acid — (alb) Ai-phenyl J-acid. 

Fusion/Hydroxylation. The conversion of arylsulfonic acids to the corresponding hydroxy compound is normally effected by heating with caustic soda (caustic fusion). The primary examples are P-naphthol in the naphthalene series and resorcinol in the benzene series further examples are m- am in oph en o1 from metanilic acid and diethyl-y -arninophenol from /V,/V-diethy1metani1ic acid. In the naphthalene series the hydroxy group is much... 

Metanilic acid (3-aminobenzenesulfonic acid) [121-47-1] M 173.2, m <300 (dec), pK from water (as the hydrate), under CO2 in a semi-darkened room. (The soln is photosensitive.) Dried over 90% H2SO4 in a vac desiccator. 

Metanil-gelb, n. metanil yellow, metaniline yellow, -saure, /. metanilic acid. 

OT-nitrobenzenesulphonic acid to metanilic acid has been run. A cathode of copper particles was used in a 1000 A unit and the overall performance of the electrode was satisfactory (Smith, 1969). 

Acid Orange 7 Sludge originally collected from a pulp and paper wastewater treatment plants Color removal of 96% was achieved in the presence of liposomes that facilitated uptake of dyes by anaerobic biomass, leading to a fast decolorization. Amines such as sulfanilic acid and aniline were mineralized by inocula with high microbiological diversity, even with domestic effluent. Orthanilic and metanilic acids and 1-amino-2-naphtol were persistent under tested conditions [176]... 

Metanilic acid, all6 Methacholine chloride, a49 Methacrolein, m27 Methacrolein diacetate, m32 Methallyl alcohol, m400 Methallyl chloride, cl82... 

In the sulphonation of aniline small amounts of the o-compound are produced along with sulphanilic acid. Aniline o-sulphonic acid, however, is of no further interest. Metanilic acid, on the other hand, is also manufactured as an intermediate in the azo-dye industry. It is obtained from nitrobenzene-m-sulphonic acid by reduction. The amino-(iand hydroxy-) sulphonic adds of the naphthalene series are of the greatest technical importance. They are either diazotised themselves or serve for coupling with other diazo-compounds. In this way the most important azo-dyes are produced. 

Mercury benzamide, 797 Mercury-sealed stirrers, 66-69, 220 Mesitaldehyde, 690, 701 Mesityl oxide, 353 Metaldehyde, 319 Metanilic acid, 586, 589 Methiodides, 660 Metho-p-toluenesulphonates, 660 p-Methoxyacetophenone, 733 p-Methoxybenzaldehyde, 690, 703 4-Methoxybenzoin, 708, 714 p-Methoxycinnamic acid, 719 p-Methoxyphenylacetic acid, 904, 905, 924, 925... 

Preparation 364.—Metanilic Acid (Aniline-m-sulphonic acid). 

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