Лако-красочные материалы — производство

In the preparation of naphthalene derivatives, good yields are ob­tained only if the naphthalene used as the starting material is of the highest purity. If a good grade of naphthalene is not at hand, it is recommended that the material be purified, first by distillation, and then by treating it with 5 per cent of its weight of concentrated sulfuric acid. Generally, however, pure naphthalene from tar distillation is avail­able today.

12. л-NitronaphthaIene and a-Naphthylamine5 5

In general, naphthalene reacts much more easily than benzene, and nitration of naphthalene takes place so energetically that polynitro compounds are formed easily. On the other hand, since the reaction is carried out at a temperature below the melting point of naphthalene, the larger particles may not be attacked by the nitric acid under the

55 See also O. N. Witt, Chetn. Ind. Get. Nachr.-Ausgabe, 10, 215 (1887); L. Paul, Z. angew. Chem., 10, 145 (1897).

conditions employed. Hence, it is necessary to pulverize the naphtha­lene to such a degree that it will pass through a sieve having 400 meshes per square centimeter.

Naphthalene crystallized aS plates is very difficult to pulverize. If such material is to be used, it should first be melted and allowed to solidify in a compact crystal­line mass which is much more easily pulverized.

To a mixture of 103 grams of 62 per cent nitric acid (40° B6) and 300 grams of 80 per cent sulfuric acid, 128 grams of naphthalene is added. The mixture is stirred continuously for 6 hours at 50°C., and then the temperature is raised to 60° during the course of 1 hour. On cooling the mixture, the nitronaphthalene floats as a porous cake on the surface of the acid. It contains about 90 to 92 per cent of the a-nitro compound, 4 to 5 per cent of the /J-nitronaphthalene, 2 to 3 per cent of dinitronaphthalene, and about 0.5 per cent of 2,4-dinitro-l-naphthol (Martius yellow).

The crude product is melted several times with boiling water to remove the acid and simultaneously distill out any residual naphthalene. The melted product is then poured into cold, well stirred water, caus­ing it to solidify in the form of small balls.

If purified nitronaphthalene is desired, the crude material is dried by melting at 120° in an air oven. It is then treated with 10 per cent of its weight of ligroin (b. p. about 150°). (Commercial xylene or cumene can also be used.) The solution is filtered hot through a smooth filter and allowed to stand for some time. The resulting cake of crystals is pressed out strongly in a cotton cloth. The purification operation is repeated until the nitronaphthalene has a melting point of 61°. It is then in the form of yellow, glistening crystals. Part of the product is lost in the mother liquors and can be recovered by distilling off the solvent.

The crude nitronaphthalene is reduced by the Bechamp method using iron and a small amount of hydrochloric acid. In an iron reduction vessel equipped with an anchor-type stirrer (Fig. 11) is placed 200 grams of iron turnings, 100 cc. water, and 10 cc. concentrated hydro­chloric acid (30 per cent). The mixture is heated in a boiling water bath, and the nitronaphthalene is added in small portions, preferably in the manner described for the reduction of p-chloro-o-nitrophenol (page 110). With continuous stirring, 173 grams (1.0 mole) of nitro­naphthalene (air-dried material) is reduced in a period of 4 hours. It is not advisable to operate more rapidly or undesired azo compounds may be formed. The mixture is now made distinctly alkaline by the addition of soda and removed from the reduction vessel. The a-naph — thylamine can be separated most satisfactorily in the laboratory by dis­tillation with superheated steam. For this purpose, the whole reaction mixture is transferred to a kettle such as that shown in Figure 29. The water is completely driven off, while the mixture is being stirred, by heating the oil bath to about 200°, and then steam, superheated to 250°, is passed in (Fig. 23a). (The figure shows a schematic apparatus with­out stirrer. Stirring is recommended, however, in order to make the separation of iron oxide and naphthylamine easier.) A rapid distilla­tion will easily carry over one-half to one part of naphthylamine with

one part of water. A small amount of very finely divided iron powder, graphite from the cast iron, and iron oxide always comes over with the base. The distillation is complete when no more product, or only colored material, comes over with a steam temperature of 260°. The whole distillation requires 1 to 1.5 hours, depending on the type of heating employed. The kettle then contains a very fine, black mass which is pyrophoric and which therefore cannot simply be thrown out. The naphthylamine is separated from the mother liquor after cooling,
melted, and dried at 110° in an air oven. Vacuum distillation of the dried product gives the base as a colorless, crystalline material. The yield from 1 mole of naphthalene is about 110 grams of pure a-naph — thylamine melting at 50°.

The reaction mixture can also be worked up in the following way. When the reduction is complete, the mixture is neutralized with soda and all of the water is evaporated under vacuum. The residue is then extracted three times with benzene, and the extract is distilled at atmospheric pressure to remove the benzene. The a-naphthylamine is then distilled under reduced pressure.

Technical Observations, (a) Nitronaphthalene. The waste acid from the nitration is always partly re-used, being brought back to 80 per cent sulfuric acid by the addition of stronger acid. The unused part of the acid is used in acidi­fying alkali fusion mixtures, and similar purposes. The nitration is almost quantita­tive if the starting material has been ground up correctly (disintegrating at 60°). Nitronaphthalene is used in the preparation of 1,5- and 1,8-dinitronaphthalenes, as well as of the diazo compound of l-amino-2-naphthol-4-sulfonic acid. In the latter preparation, nitronaphthalene, heated with bisulfite, gives l-naphthylamine-2,4- disulfonic acid along with some naphthionic acid. The disulfonic acid is diazotized and converted to the diazo compound of l-amino-2-naphthol-4-sulfonic acid by treatment with sodium bicarbonate and sodium hypochlorite. This remarkable series of reactions is shown below:66

This process, although good, has been replaced by the less expensive Sandmeyer process (page 202).

(b) а-Naphthylamine. The reduction is carried out in apparatus similar to that already described. However, paddle or propeller stirrers cannot be used be­cause of the pasty consistency of the reaction mixture, and only anchor-type stirrers are usable, such as the one shown in Figure 31. The steam distillation is done in apparatus such as the one shown in Figure 24, in which the steam is heated in a superheater. Various satisfactory models of this equipment are supplied by different manufacturers.

In large scale operations, a large part of the naphthylamine can be drawn off directly as a liquid. The residue of iron, iron oxide, and a-naphthylamine is mixed with sawdust and extracted several times with benzene. The mixture of [36]
iron, iron oxide, and sawdust is freed of benzene by steam and then sent to the foundry where it is used as a binding material for briquetting of iron turnings for the cupola furnace.

a-Naphthylamine is used as an end component or especially as a middle com­ponent, in the preparation of many important azo dyes; it is also used in the preparation of dyes of other classes, a-Naphthylamine is the starting material for the synthesis of a whole series of dye intermediates, some of which are described below. Like aniline, о-naphthylamine has found a new and interesting application outside of the dye field. It is used in North America and Australia in refining some of the poorer ores by the flotation process. In this process, the finely stamped ore is mixed vigorously (emulsified) with about one-half of one per cent of its weight of naphthylamine and crude xylene and a large quantity of water. The heavy ore, despite its high specific gravity, collects with the foam on the surface ana can easily be scooped off.

Phenyl-a-naphthylamine

In a round-bottomed flask fitted with a thermometer and a vertical tube, a mixture of 143 grams (1.0 mole) of a-naphthylamine, 175 grams of aniline, and 3 grams of sulfanilic acid is boiled vigorously for 42 hours. Ammonia is liberated and the boiling point of the mixture increases to 215°C. from an initial value of about 195°. When the reaction is com­pleted, the mixture is fractionated carefully in vacuum. Three frac­tions are taken: about 80 grams of aniline, about 10 grams of an inter­mediate fraction containing some aniline, a little a-naphthylamine, and mainly phenyl-a-naphthylamine, and finally, 190 to 200 grams of phenyl- a-naphthylamine which solidifies at about 53°. The residue is worth­less and is discarded. This method, which is generally used today, gives a purer product than is obtained when the condensation is carried out with hydrochloric acid. Little or no diphenylamine is formed, and the reaction can be carried out on a large scale in an iron vessel. At 12 mm. pressure, the boiling point of aniline is about 73°, of a-naphthylamine about 160°, and of phenyl-a-naphthylamine about 224°.

Phenyl-a-naphthylamine, as well as the alkyl derivatives of a-naphthylamine, is used in preparing basic diphenylnaphthylmethane dyes (Victoria blue).

A mixture of 143 grams of a-naphthylamine, 110 grams of 66° Вё sulfuric acid, and 1 liter of water is heated at 200°C. under 14 at­mospheres pressure. The naphthylamine should first be melted in the water and the acid added in a thin stream with good stirring. The auto­clave should be either leaded or enameled, although the cover can be of iron, since the sulfuric acid is not volatile. It is necessary that the autoclave be heated in an oil bath, because any overheating might cause the lead to melt.

After 8 hours, the mixture is allowed to cool and the a-naphthol is separated from the mother liquor. Ammonium sulfate is recovered from the latter. The product is melted with a little water and, after cooling, separated from the liquid. It is almost chemically pure. Completely pure material is obtained by vacuum distillation. The yield of a-naph­thol melting at 94° is 94 to 95 per cent of the theoretical amount.

Technical Observations. The process described above is the best and least expensive. There is, however, another method which is analogous to the prepara­tion of /З-naphthol. Sodium naphthalene-a-sulfonate is fused with caustic soda at 290° (not to exceed 300°). The sulfonation is carried out at 80-90°, and the product is salted out in as concentrated a solution as possible. The sulfonate can also be isolated by removing the excess acid with lime or chalk, treating with soda, and evaporating to obtain the product. The sulfonate, thus obtained, can be used in the fusion without further purification, but the resulting a-naphthol is impure.

Naphthionic Acid from a-Naphthylamine

Naphthionic acid is prepared from naphthylamine acid sulfate by the baking process, i. e., long, dry heating, preferably under reduced pressure.

SO, H

(a) Preparation of the Acid Sulfate

In a three-neck flask fitted with thermometer, stirrer, and vertical condenser, 73.5 grams of 70 per cent sulfuric acid is heated to 120-125°,

and then a warm (50°) solution of 75 grams of a-naphthylamine in about 15 grams of benzene is added with thorough stirring, during a 30-minute period. The formation of clumps of undissolved base is com­pletely avoided in this way, and the benzene distills out slowly. The light reddish solution soon solidifies, and the resulting solid is dried at 120° in vacuo for 18 hours. A very pure acid sulfate, which is of the greatest importance in the baking process, is obtained by the use of 70 per cent sulfuric acid and pure a-naphthylamine.

The conversion of a-naphthylamine sulfate into naphthionic acid is carried out in a vacuum baking apparatus constructed as shown in Fig­ure 30. 75 grams of the finely powdered sulfate is heated for 8 hours at 180° under a pressure of 10-15 mm. After the heating a light gray mass remains. This is dissolved in about 500 cc. water to which 20 grams of anhydrous soda has been added. The solution is heated to boiling and filtered, and then extracted with benzene to remove unchanged naph­thylamine. The solution is again heated to boiling and hydrochloric acid is added until a slight turbidity is formed. Decolorizing carbon is added, the solution is filtered hot, and the filtrate is cooled and acidi­fied with hydrochloric acid. The colorless naphthionic acid which separates is filtered off and dried at 100°. The yield is 60 to 65 grams, or 85 to 95 per cent of the theoretical amount.

The general principles of the baking process are discussed on page 127 ff.

l —

Naphthol-4-sulfonic Acid (Nevile-Winther Acid) from
Naphthionic Acid (Bucherer Reaction)

A mixture of 100 grams of 100 per cent naphthionate in 200 cc. water and 600 grams of sodium bisulfite solution (25 per cent S02) is boiled under reflux for 1 day. Sufficient 30 per cent sodium hydroidde solution is then added to cause the solution to give a red test with thiazole paper, and the solution is boiled as long as ammonia is liber­ated, then acidified with hydrochloric acid. Crystalline Nevile-Winther acid is obtained on cooling. It is freed from residual naphthionic acid by dissolving in water and filtering. The yield is about 80 per cent of the theoretical amount.

Naphthols as well as naphthylamines are converted to labile intermediate com­pounds by the action of bisulfite. These intermediates were considered to be sulfurous acid esters of naphthols (Formula I) by Bucherer, the discoverer of the reaction, but Woroshtzow formulated them as addition products of bisulfite with the keto forms of the naphthols (Formula II). These intermediates yield the cor­responding naphthylamines with ammonia, and are hydrolyzed to the naphthols by caustic alkali. Thus, it is possible to convert naphthols into naphthylamines (pages 200 and 203), as well as naphthylamines into naphthols.[37]

Furthermore, ammonia can be replaced by primary or secondary aliphatic or aromatic amines (the latter, however, only in (he p series), thus affording a means of preparing alkylated or arylated naphthylamines starting with either the primary naphthylamine or the corresponding naphthol.[38]

The Bucherer reaction is also applicable with certain compounds in the benzene and anthracene[39] series, but it is of practical significance only with naph­thalene compounds. The reaction can be used with both a — and ^-naphthols or
-naphthylamines. It does not work, however, if a sulfo group is present in the position ortho or meta to an a—OH or —NH2, or meta to a p—OH or —NH2. Thus, for example, in J acid (2-amino-5-naphthol-7-sulfonic acid) or Gamma acid (2- amino-8-naphthol-6-sulfomc acid), the reaction involves only the amino group and not the hydroxyl group which is “protected” by the meta sulfo group (cf. pnenyl — gamma acid, page 209). Similarly, the reaction with 2,8-dihydroxynaphthalene-6- sulfonic acid involves only the hydroxyl group in the 2 position (page 208).

l-Naphthol-4-sulfonic acid can be prepared also by diazotizing naphthionic acid. It is used chiefly as an azo dye component.