(1)HOC6H4OH(4) + O(Na2Cr2O7 + H2SO4)—> O=C6H4=O + H2O Prepared by E. B. VLIET. Checked by ROGER ADAMS and E. E. DREGER.

1. Procedure

IN a 2.5-l. beaker, 100 g. of hydroquinone are dissolved in 2000 cc. of water heated to about 50'0. After the solid is completely dissolved, the solution is cooled to 20'0, 100 g. of concentrated sulfuric acid are slowly poured in, and the mixture is again cooled to 20'0. A concentrated solution of technical sodium dichromate is prepared by dissolving 140 g. in 65 cc. of water. This solution is then added gradually to the hydroquinone solution, with the use of a mechanical stirrer (see notes), the mixture being cooled so that the temperature never rises above 30'0. At first a greenish-black precipitate forms, but upon further addition of the sodium dichromate solution, the color changes to yellowish green. As soon as this color remains permanent (a slight excess of sodium dichromate does no harm) the reaction is complete. This requires about one-half to three-quarters of an hour; 90 to 110 cc. of sodium dichromate solution is necessary. The mixture is then cooled to about 10'0 and filtered with suction. As much water as possible is pressed out of the crystals.

The filtrate is extracted twice, 150 cc. of benzene being used for each extraction. The precipitate of quinone is transferred to a 1-l. beaker, and 500 cc. of benzene, including the 300 cc. used to extract the filtrate, are added, The mixture is now heated with stirring on a steam-bath, and as soon as most of the quinone has dissolved the benzene layer is decanted into another beaker. It is dried while hot by stirring a short time with a little calcium chloride, and then filtered through an ordinary funnel into a 1-l. distilling flask before it cools. There is a certain amount of quinone which does not go into the 500 cc. of benzene, so that the residue is extracted a second time with about 100 cc. of benzene, which is dried and filtered with the first extract. During these extractions, the benzene should not be at the boiling point, as this will cause a considerable volatilization of the quinone.

The distilling flask is now attached to a condenser set for downward distillation, and the benzene is distilled. As soon as the quinone starts to separate, the residue in the flask is transferred to a beaker and cooled in an ice bath. The precipitate is filtered off with suction and the product spread out for a short time to dry. The product is yellow in color and weighs 75 to 80 g. (76-81 per cent of the theoretical amount). Material made in this way will hold its yellow color over long periods of time, provided it is protected from light.

The benzene distillate is yellow and contains some quinone. This, as well as the benzene from the final filtration of the quinone crystals, may be used in a subsequent run and thus raises the yield of the subsequent runs to about 85-90 g. (85-90 per cent of the theoretical amount).

2. Notes

As the mixture becomes thick during the oxidation, it is very necessary to use a stirrer which will keep the whole mass agitated by reaching to the sides and bottom of the beaker.

If impure hydroquinone is used, a black, sticky precipitate will usually appear after the addition of the sulfuric acid to the hydroquinone solution. This should be removed, before the oxidation is started, by filtration without suction through a fluted filter.

When technical sodium dichromate is used, the solution should be filtered with suction, before it is added to the hydroquinone, in order to remove any insoluble impurities.

In the laboratory it is convenient to make several small runs of the size indicated, as far as the oxidation is concerned; but the benzene extractions can be combined.

It is also possible to obtain good yields of quinone in the following manner: 1500 cc. of water, 465 g. of concentrated sulfuric acid and 300 g. of hydroquinone are mixed in a 3-l. beaker. The mixture is cooled to 0'0, and 330 g. of sodium dichromate are added in powdered form, the temperature being kept below 5'0 at all times. This procedure requires a longer time and much more care in the control of conditions than the method described above.

3. Other Methods of Preparation

Quinone may be prepared by the oxidation of aniline with dichromate or manganese dioxide and sulfuric acid.[1] This is a more feasible commercial method than the one given. However, the oxidation of hydroquinone is more rapid and convenient and, hence is more desirable for use in the laboratory. Various materials have been oxidized by chemical means to give quinone: they are quinic-acid,[2] hydroquinone,[3] benzidine,[4] p-phenylenediamine,[5] sulfanilic acid,[6] p-phenolsulfonic acid,[7] arbutin,[8] aniline black,[9] and the leaves of various plants.[10] Quinone is also formed by several other methods: by the fermentation of fresh grass;[11] by the action of iodine on the lead salt of hydroquinone;[1b] by the decomposition of the compound, C6H4<.>2CrO2Cl with water;[2b] by the action of sulfuric acid on phenol blue;[3b] by the electrochemical oxidation of aniline,[4b] hydroquinone[5b] or benzene;[6b] by the catalytic oxidation of benzene.[7b]

[1] Jahresb. 1863, 415; Ber. 10, 1934, 2005 (1877); 16, 687 (1883); 19, 1468 (1886); 20, 2283 (1887); 31, 1524 (1898); Ann. 200, 240 (1880); 215, 127 (1882).

[2] Ann. 27, 268 (1838).

[3] Ann. 51, 152 (1844) j Am. Chem. J. 14, 555 (1892).

[4] Jahresb. 1863, 415.

5 Jahresb. 1863, 422.

6 Ann. 159, 7 (1871); Ber. 8, 760 (1875).

[7] Ber. 8, 760 (1875).

[8] Ann. 107, 233 (1858).

[9] Ber. 10, 1934 (1877); 34, 1285 (1901).

[10] Ann. 89, 247 (1854); Ber. 34, 1162 (1901).

[11] Ber. 30, 1870 (1897).

[1b] Ber. 31, 1458 (1898); Am. Chem. J. 26, 20 (1901).

[2b] Ann. chim. phys. (5) 22, 270 (1881).

[3b] Ber. 18, 2915 (1885); 21, 889 (1888).

[4b] D. R. P. 109,012; Frdl. 5, 664 (1900); D. R. P. 117,129; Frdl. 6, 112 (1901); J. Soc. Dyers and Colourists, 36, 138 (1920).

[5b] D. R P. 117,129; Frdl. 6, 112 (1901).

[6b] D. R. P. 117,251; Frdl. 6, 109 (1901); U. S. Pat. 1,322,580 (1919); C. A. 14, 287 (1920); Rev. produits chim. 21, 219 (1918); 21, 288 (1918).

[7b] U. S. Pat. 1,318,631 (1919); C. A. 14, 70 (1920).

XXIII

SODIUM p-TOLUENESULFINATE

2CH3C6H4SO2Cl + 3Zn—> (CH3C6H4SO2)2Zn + ZnCl2 (CH3C6H4SO2)2Zn + Na2CO3—> 2CH3C6H4SO2Na + ZnCO3

Prepared by FRANK C. WHITMORE and FRANCIS H. HAMILTON Checked by J. B. CONANT and PAUL ALLEN, JR.

1. Procedure

FIVE HUNDRED grams of technical p-toluenesulfonyl chloride are ground in a mortar to break up all lumps. Three liters of water are placed in a 12-l. crock provided with a large brass stirrer and a tube for passing steam directly into the liquid. Dry steam is passed into the water until the temperature reaches 70'0. The steam is then shut off and 400 g. of zinc dust (90 to 100 per cent pure) is added. The sulfonyl chloride is then added in small portions by means of a porcelain spoon. The addition takes about ten minutes. The temperature rises to about 80'0. Stirring is continued for ten minutes after the last of the chloride has been added. Steam is then passed into the mixture until the temperature reaches 90'0. If it is heated any hotter, bumping takes place. The steam is shut off, and 250 cc. of 12 N. sodium hydroxide solution is added. Finely powdered sodium carbonate is then added in 50-g. portions until the mixture is strongly alkaline. The mixture froths considerably, but this causes no trouble unless too small a crock is used. The stirrer is loosened and the crock is removed. The mixture is filtered by suction in a large funnel. The filtrate has a volume of about 4.5 l. The cake of unchanged zinc dust and zinc compounds is transferred to a 3-l. battery jar and placed under the stirrer, and the latter is clamped in place. Water (750 cc.) is added, the stirrer is started, and steam is passed in until the mixture starts to froth too violently. The steam is then shut off, but the stirring is continued for ten minutes. The mixture is filtered and the filtrate is added to the main solution in a large evaporating dish. The liquid is evaporated over a large burner to a volume of about 1 l., or until a considerable crust forms around the edges. The mixture is then cooled. Large, flat, transparent crystals separate. The thoroughly cooled mixture is filtered by suction, and the crystals are air-dried until efflorescence just starts. They are then bottled. The product is CH3C6H4SO2Na<.>2H2O. Yield 360 g. (64 per cent of the theoretical amount). Careful acidification of the mother liquor with dilute hydrochloric acid yields 15 g. of the free sulfinic acid.

2. Notes

The free sulfinic acid may be prepared by dissolving the sodium salt in cold water and carefully acidifying the solution with hydrochloric acid. An excess of the latter must be avoided, as it dissolves the acid to a certain extent. The sulfinic acid is difficult to dry without partial conversion into the sulfonic acid.

3. Other Methods of Preparation

Toluenesulfinic acid and its salts have been prepared by three general methods: (1) The reduction of the sulfonyl chloride. The reagents which have been used for this are sodium amalgam,[1] zinc dust in alcohol or water,[2] sodium sulfite,[3] sodium sulfide,[4] potassium hydrosulfide[5] (the thio acid being first formed) and sodium arsenite.[6] (2) From toluene by the Friedel and Crafts reaction, using either sulfur dioxide and hydrogen chloride[7] or sulfuryl chloride.[8] (3) From p-toluidine by diazotization and subsequent treatment with sulfur dioxide and finely divided copper.[1b] The compound has also been obtained in certain reactions which, however, would not be suitable for preparative work; thus it is formed by hydrolysis and reduction of certain thio derivatives[2b] prepared from the acid itself and also by the decomposition of ditolylsulfonmethylamine.[3b]

[1] Ann. 142, 93 (1867).

[2] Ber. 9, 1586 (1876).

[3] Ber. 3, 965 (1870).

[4] D. R. P. 224,019; Chem. Zentr. 1910, (II), 513.

[5] Ber. 42, 3821 (1909).

[6] Ber. 41, 3351 (1908); Ber. 42, 480 (1909).

[7] Ber. 41, 3318 (1908); J. Chem. Soc. 93, 754 (1908).

[8] Rec. trav. chim. (2) 30, 381 (1911).

[1b] Ber. 32, 1141 (1899); J. Chem. Soc. 95, 344 (1909).

[2b] Ber. 15, 130 (1882); 20, 2088 (1887); 41, 3351 (1908).

[3b] J. prakt. Chem. (2) 63, 170 (1901).

XXIV

1,3,5-TRINITROBENZENE

C6H2(NO2)3CO2H—> C6H3(NO2)3 + CO2

Prepared by H. T. CLARKE and W. W. HARTMAN. Checked by J. B. CONANT and J. J. TOOHY.

1. Procedure

THE crude trinitrobenzoic acid obtained by oxidation of 360 g. of trinitrotoluene (prep. XXV, p. 95) is mixed with 2 l. of water at 35'0 in a 5-l. flask provided with a stirrer. Fifteen per cent sodium hydroxide solution is added, with continuous stirring, until a FAINT red color is just produced. (See Notes.) The color is then immediately discharged by means of one or two drops of acetic acid, and the liquid is filtered from unchanged trinibrotoluene. The filtrate is transferred to a 5-l. flask, and 70 cc. of glacial acetic acid are added. The mixture is then gently heated, with continuous stirring, when trinitrobenzene separates in crystalline condition, and floats on the surface of the liquid as a frothy layer. After about one and a half hours the evolution of gas ceases; at this point the crystals begin to stir into the solution. The heating and stirring is continued for three-quarters of an hour, when the mixture is allowed to cool, and the crystals filtered off. A sample of the filtrate should be tested for undecomposed trinitrobenzoic acid: if a precipitate is produced by the addition of sulfuric acid the process must be continued. After recrystallization from glacial acetic acid, the product melts at 121-122'0. The yield is 145-155 g. (43 to 46 per cent of the theoretical amount calculated from the trinitrotoluene). 2. Notes

During the solution of the trinitrobenzoic acid, the temperature should not be below 35'0, owing to the slight solubility of trinitrobenzoic acid in cold water. The heat of neutralization raises the temperature to 45-55'0, but the latter temperature should not be exceeded, since any trinitrobenzene formed at this point would later be removed with the unreacted trinitrotoluene.

Care must be taken that no more alkali is added than is just sufficient to produce the faint red color. If an excess of alkali is added it produces a permanent color, which is not removed by acid and colors the final product.

When once the evolution of carbon dioxide sets in, the flame must be cut down so as to avoid the formation of a thick layer of froth which might foam over.

3. Other Methods of Preparation

1,3,5-Trinitrobenzene can be prepared by heating m-dinitrobenzene with nitric acid and sulfuric acid to 120'0;[1] by heating 2,4,6-trinitrotoluene with fuming nitric acid in a sealed tube at 180'0 for three hours;[2] by heating 2,4,6-trinitrobenzoic acid or its sodium salt with water, alcohol, dilute sodium carbonate or other suitable solvent.[3]

[1] Ber. 9, 402 (1876); Ann. 215, 344 (1882).

[2] Ber. 16, 1596 (1883).

[3] D. R. P. 77,353; Frdl. 4, 34 (1894).

XXV

2, 4, 6-TRINITROBENZOIC ACID

C6H2(NO2)3CH3 + 3O(Na2Cr2O7 + H2SO4)—> C6H2(NO2)3CO2H + H2O

Prepared by H. T. CLARKE and W. W. HARTMAN. Checked by J. B. CONANT and J. J. TOOHY.

1. Procedure

To 3600 g. of concentrated sulfuric acid, in a 5-l. flask placed in an empty water bath, are added 360 g. of technical trinitrotoluene, while the mixture is stirred mechanically. Sodium dichromate (Na2Cr2O7 2H2O) is now added in small quantities (PRECAUTION: see Notes), with constant stirring, until the temperature of the mixture reaches 40'0; the empty water bath is now filled with cold water and the addition of sodium dichromate continued at such a rate that the temperature remains at 45-55'0. In all 540 g. of sodium dichromate are added, the addition taking one to two hours. When all has been added, the mixture, which has now become very thick, is stirred for two hours at 45-55'0, and poured into a crock containing 4 kg. of crushed ice. The insoluble trinitrobenzoic acid is filtered off, and carefully washed with cold water until free from chromium salts. On drying it weighs 320-340 g.

The product is now mixed with 2 l. of distilled water at 35'0 in a 5-l. flask provided with a stirrer, and 15 per cent sodium hydroxide solution is dropped in with continuous stirring until a FAINT red color is just produced. Should this disappear, it is restored by the addition of a few drops more. When it has persisted for five minutes, the color is discharged by the addition of a few drops of acetic acid, and the insoluble unattacked trinitrotoluene filtered off and washed with a little water. The trinitrobenzoic acid is precipitated from the filtrate by the addition of a slight excess of 50 per cent sulfuric acid. The solution is chilled, and the acid filtered and washed free from salts with ice water. When dried in air it weighs 230-280 g. (57 to 69 per cent of the theoretical amount).

2. Notes

The mother liquors and washings lose carbon dioxide on boiling, and the insoluble trinitrobenzene separates see preparation XXIV); after filtering, washing, and drying, it weighs 15-20 g. (4 to 6 per cent of the theoretical amount).

It is essential that the stirring should be most efficient, so that when the mixture becomes thick the dichromate will be evenly distributed throughout the liquid, as rapidly as it is added. If the stirring is not efficient, local reactions of extreme violence (in certain cases leading to conflagration) will occur. An iron stirrer may be employed in the oxidation reaction, but not in the purification.

Technical sodium dichromate generally contains a certain amount of chlorides, and the chlorine liberated from these tends to cause a troublesome foam towards the end, of the reaction. Only a very efficient stirrer, which draws down the surface of the liquid, is able to combat this difficulty. The amount of solid sodium dichromate given is for the dry crystalline compound containing two molecules of water of crystallization.

Great care should be taken in dissolving the crude acid in the alkali.
If an excess of alkali persists for any length of time, a permanent
color is produced which will discolor the final product.
The acid is fairly soluble in cold water and should be washed with care.

3. Other Methods of Preparation

2,4,6-Trinitrobenzoic acid has been prepared by heating trinitrotoluene with fuming acid in a sealed tube to 100'0, for two weeks,[1a] the oxidation being only partial. It can also be prepared by heating trinitrotoluene under a reflux condenser, with a mixture of 5 parts of concentrated nitric acid and 10 parts of concentrated sulfuric acid;[1] this method is, however, unsuitable in the laboratory owing to the difficulty of devising suitable apparatus. Another method is to dissolve trinitrotoluene in nitric acid and, to this solution (at 95'0), to add potassium chlorate at such a rate that the temperature does not fall;[2] this method has been found to be difficult to control on a laboratory scale.

[1a] Ber. 3, 223 (1870)

[1] D. R. P. 77,559; Frdl. 4, 34 (1894)

[2] D. R. P. 226,225; Frdl. 10, 167 (1910).

The method described above is a modification of a patented process,[3] in which trinitrotoluene suspended in sulfuric acid is treated with chromic anhydride.

[3] D. R. P. 127,325; Frdl. 6, 148 (1901).

INDEX

A

Acetic acid, 18, 33, 64 Acetone, 41 Acetophenone, 1 Ammonium carbonate, 75 Ammonium hydroxide, 37, 75 Aniline, 71, 79 Anthranilic acid, 47

B

Benzalacetophenone, 1 Benzaldehyde, 1, 5 Benzoic acid, 5 Benzyl alcohol, 5 Benzyl benzoate, 6 Benzyl chloride 9 Benzyl cyanide, 9-11, 27, 57, 63 Bromostyrene, 67

C

Carbon tetrachloride, 23 Chlorine, 37 Copper sulfate, 38

D

Dibenzyl ether, 6 a, g-Dichloroacetone, 13-15 Dimethylaminobenzaldehyde, 17-21 Dimethylaniline, 17, 47

E

Ethyl alcohol, 23, 27 Ethyl oxalate, 23-26 Ethyl phenylacetate, 27-28

F

Ferrous sulfate, 79 Formaldehyde, 17

G

Gelatine solution, 37 Glycerol, 29, 33, 79 Glycerol a, g-dichlorohydrin, 29-31 Glycerol a-monochlorohydrin, 33-35

H

Hydrazine sulfate, 37 40 Hydrochloric acid, 17, 30, 34, 47, 71 Hydroquinone, 85

M

Mesitylene, 41-45 Methyl red, 47-61

N

Naphthol, 61 Nitric acid, 57 Nitrobenzene, 79 p-Nitrobenzoic acid, 63-66 p-Nitrobenzyl cyanide, 67-58, 59 p-Nitrophenylacetic acid, 6940 Nitrosodimethylaniline hydrochloride, 17 Nitroso-,3-naphthol, 61-62 Nitrotoluene, 53

O

Oxalic acid, 23

P

Phenylacetic acid, 10, 63-65 Phenylacetylene, 67-69 Phenylhydrazine, 71-74 Phthalic anhydride, 75 Phthalimide, 7~78 Potassium hydroxide, 67

Q Quinoline, 79 83 Quinone, 86 88 S

Sodium acetate, 48 Sodium benzylate, 6 Sodium cyanide, 9 Sodium dichromate, 13, 53, 85, 95 Sodium hydroxide, 1, 37, 61, 93 Sodium hypochlorite, 37 Sodium, metallic, 5, 42

Sodium nitrite, 17, 47, 61, 71, 80 Sodium sulfite, 71 Sodium p-toluene sulfinate,—91 Sulfur dioxide, 71 Sulfuric acid, 13, 27, 30. 34, 37, 41, 43, 53, 57, 59, 63, 79, 85, 95

T Toluene, 48 Toluenesulfonyl chloride, 89 I, 3, s-Trinitrobenzene, 93— 94, 96 2, 4, 6-Trinitrobenzoic acid, 93, 96 97 2, 4, 6-Trinitrotoluene, 93, 95 Zinc dust, 89