C6H5CH=CHBr + KOH—> C6H5CTBCH + KBr + H2O
Prepared by JOHN C. HESSLER. Checked by J. B. CONANT and E. R. BARRETT.
IN a 500-cc. Pyrex distilling flask are placed 150 g. of potassium hydroxide. The mouth of the flask is provided with a one-hole stopper holding a dropping funnel; the side tube of the flask is connected with a condenser set for downward distillation. The b-bromostyrene (100 g.) is placed in the dropping funnel.
The distilling flask is gradually heated in an oil bath until the temperature of the bath is 200'0, and the bromostyrene is then dropped in upon the molten potassium hydroxide, at the rate of somewhat less than a drop a second. Since the boiling point of phenylacetylene is 142-143'0, and that of bromostyrene is 218-220'0, the phenylacetylene distils away from the unchanged bromostyrene.
While the bromostyrene is being dropped in, the temperature of the oil bath is raised very gradually to 215-220'0, and is kept at this temperature until all the bromostyrene has been added. Finally the temperature is raised to 230'0, and is held there until no more distillate comes over. The distillate is colorless; it consists of two layers, the lower one being water. The upper layer is separated and dried with solid potassium hydroxide. It is then distilled. The yield of the distilled phenylacetylene, boiling at 142-144'0, is 37 g. (67 per cent of the theoretical amount). 2. Notes
Toward the end of the reaction, a crust of potassium bromide may tend to cover the melted potassium hydroxide. One can break the crust by shaking the distilling flask gently, or by using a glass rod inserted through a second hole in the stopper holding the dropping funnel.
It is convenient to have such a rod or stirrer passing through a mercury seal in the stopper of the flask. An occasional turn of this stirrer breaks the crust and facilitates the operation. Mechanical stirring should not be employed, as it reduces the yield tremendously. Apparently this is because it facilitates the solution of bromostyrene in the tarry by-products and thus causes it to polymerize instead of reacting with the potassium hydroxide. A single Pyrex flask can be used for only three or four runs. The flask should be emptied while still very hot.
The yield of material can be somewhat increased by working with small lots (25 g. of bromostyrene).
The use of steel or copper vessels in place of a glass flask seems to diminish the yield slightly.
3. Other Methods of Preparation
Phenylacetylene has been prepared by the elimination of carbon dioxide from phenylpropiolic acid by means of phenol or aniline or by heating with barium hydroxide; from styrene dibromide, by heating with potassium hydroxide in alcohol; by heating b-bromo or chloro styrene with sodium ethylate or potassium hydroxide in alcohol; by passing the vapors of a-dichloroethylbenzene over hot soda lime; by the action of alcoholic potassium hydroxide on dibenzal-acetone tetra-bromide;[1b] by the action of aqueous potassium hydroxide on phenyl propargylaldehyde;[2b] by the action of molten potassium hydroxide on b-bromo-styrene.[3b]
 Ber. 20, 3081 (1887).
 Rec. trav. chim. 16, 157 (1896).
 Arm. 221, 70 (1883).
 Ann. 154, 155 (1870); 235, 13 (1886); Bull. soc. chim. 35, 55 (1881); (3) 25, 309 (1901).
 Ann. 308, 265 (1899); 342, 220 (1905).
 Jahresb. 1876, 308; Gazz. chim. ital. 22 (2), 67 (1892); Bull. soc. chim. (3) 25, 309 (1901).
[1b] Ber. 39, 4146 (1900).
[2b] Ber. 31, 1023 (1898).
[3b] J. Am. Chem. Soc. 44, 425 (1922).
C6H5NH2HCl + NaNO2 + HCl—> C6H5N2Cl + NaCl + 2H2O C6H5N2Cl + 4H(Na2SO3)—> C6H5NHNH2HCl
Prepared by G. H. COLEMAN. Checked by J. B. CONANT and H. R. THOMPSON.
IN a 12-l. round-bottom flask, fitted with a mechanical stirrer, are placed 1045 cc. of concentrated commercial hydrochloric acid (sp. gr. 1.138). The flask is surrounded with a freezing mixture of ice and salt, and when the contents are at 0'0, stirring is started and 500 g. of cracked ice are added; then 372 g. of aniline, also cooled to 0'0, are run in during five minutes. The mixture is treated with 500 g. more of cracked ice, and a cold solution (0'0) of 290 g. of technical sodium nitrite dissolved in 600 cc. of water are allowed to run in slowly (twenty to thirty minutes) from a dropping funnel, the end of which is drawn to a small tip, and reaches nearly to the bottom of the flask. During this addition, the stirrer is operated rather vigorously, and the temperature is kept as near 0'0 as possible by the frequent addition of cracked ice (about 1 kg).
In the meantime, a sodium sulfite solution is prepared by dissolving 890 g. of sodium hydroxide, of about 90 per cent purity, in about 1 l. of water and then diluting to 6 l. A few drops of phenolphthalein solution are added and sulfur dioxide passed in, first until an acid reaction is indicated and then for two or three minutes longer. During the addition of the sulfur dioxide, the solution is cooled with running water. On account of the strong alkaline solution, the original color produced by the phenolphthalein is very faint, but this slowly increases until it becomes deep just before the acid point is reached. It is best to remove a small sample of the liquid from time to time, dilute with three or four volumes of water and add a drop more of phenolphthalein.
The sodium sulfite solution is placed in a 12-l. flask and cooled to about 5'0. Approximately 500 g. of cracked ice are added, and then, with mechanical stirring, the diazonium salt solution is run in as rapidly as possible. The mixture becomes a bright orange-red. The flask is now warmed to about 20'0 on a steam bath, until the solid sodium sulfite, which has separated while cooling, redissolves. The total amount of liquid is now about 10 l. One-half of this is poured into another 12-l. flask, and both halves are warmed on the steam bath to 60-70'0, until the color becomes quite dark (thirty to sixty minutes). Sufficient hydrochloric acid (300-400 cc.) is now added to each flask to make the solutions acid to litmus. The heating is continued and the color gradually becomes lighter until, after four to six hours, the solutions have become nearly colorless; they may be heated overnight, if desired.
To the hot solutions are now added about one-third of their volume of concentrated hydrochloric acid (2 l. to each portion) and the mixtures cooled, first in running water, then in a freezing mixture, to 0'0. The phenylhydrazine hydrochloride precipitates in the form of slightly yellowish or pinkish crystals which may be filtered off and dried.
The free base is liberated by adding to the phenylhydrazine hydrochloride 1 l. of a 25 per cent solution of sodium hydroxide. The phenylhydrazine separates and is taken up with benzene (two 300-cc. portions). The combined extractions are well dried with 200 g. of solid sodium hydroxide, poured off, and distilled. Most of the benzene may be distilled under ordinary pressure, and the remainder, and any low-boiling impurities, under diminished pressure. The pure phenylhydrazine boils at 137-138'0/18 mm., and is obtained as a pale-yellow liquid. It can be crystallized on cooling in an ice bath; the crystals melt at 230. The crude phenylhydrazine from two lots of aniline (744 g.) is best distilled at one time and gives 695-725 g. of pure product (80-84 per cent of the theoretical amount).
If the sodium sulfite solution contains an excess of alkali, a black tar tends to form when the solution is warmed, and very little phenylhydrazine is obtained. Great care must be taken in determining the end point in the neutralization of the sodium hydroxide by the sulfur dioxide.
If the sodium sulfite-diazonium salt mixture is acidified before warming or before becoming dark, the red color of the solution does not disappear on heating, and the precipitated phenylhydrazine hydrochloride obtained is colored red.
The benzene solution of phenylhydrazine should be well dried before distilling, since the presence of moisture causes an increased amount of foaming to take place just after the benzene has distilled off. When the distillation is carried out carefully, practically no phenylhydrazine distils with the benzene or other low-boiling impurities.
In order to obtain the maximum yield, it is necessary to cool the hydrochloric acid solution of the phenylhydrazine hydrochloride from 20'0 to 0'0, before filtration. From 5 to 10 per cent of product separates between these two temperatures. When this is done, no more phenylhydrazine hydrochloride is obtained by concentration of the mother liquor. An increase in the amount of hydrochloric acid above 2 l. for the precipitation of the hydrochloride produces no increase in yield of product.
Most published directions for the preparation of phenylhydrazine specify the use of zinc dust and acetic acid following the reduction with sodium sulfite. No improvement in the quality or quantity of the product was obtained by using zinc and acetic acid.
It is best to use freshly prepared sodium sulfite for the reduction, since the commercial quality is poor and gives a lower yield of phenylhydrazine. A cylinder of liquid sulfur dioxide should, of course, be available.
The rapid addition of the diazonium salt solution to the sodium sulfite seems to be advantageous.
Pure phenylhydrazine dissolves in dilute acetic acid to yield a perfectly clear solution.
The phenylhydrazine hydrochloride may be purified by crystallizing from water. A 600-cc. portion of water is used for 100 g. of crude hydrochloride, and the solution boiled a short time with a few grams of animal charcoal. After filtering, 200 cc. of concentrated hydrochloric acid are added, and the mixture cooled to 0'0. Pure white crystals in a yield of 85-90 g. are obtained.
Rubber gloves should be worn when working with large quantities of phenylhydrazine, since the product may cause serious injury to the skin. The vapors of phenylhydrazine should not be inhaled.
3. Other Methods of Preparation
Phenylhydrazine has been prepared by the reduction of benzene diazonium salts with sulfites; by the reduction of benzene diazonium chloride with stannous chloride; by the reduction of benzene diazonium hydrate with zinc or sulfur dioxide; by the reduction of sodium benzene diazotate with sodium stannite; by the reduction of diazoamino benzene; by the reduction of nitrosophenyl hydroxylamine or its methyl ether; and by the action of hydrazine hydrate on phenol.
 Ann. 190, 79 (3878); Ber. 20, 2463, (1887).
 Ber. 16, 2976 (1883); 17, 572, footnote (1884).
 Ber. 31, 346 (1898).
 Ber. 36, 816 (1903).
 Ber. 31, 582 (1898).
 Ann. 190, 77 (1878).
 Ber. 31, 2910 (1898).
The most feasible method consists in the reduction of diazonium salts with sodium sulfite. Although this method is given in several laboratory manuals, the results were not found entirely satisfactory. The present directions provide for a lengthy but essential heating of the diazonium-sulfite mixture, omit the useless zinc dust reduction, and supply exact details for preparation on a fairly large laboratory scale.
PHTHALIMIDE CO CO C6H4O + NH4OH—> C6H4NH + 2H2O CO CO CO CO 2C4O + (NH4)2CO3—> 2NH + CO2 + 3H2O CO CO
Prepared by W. A. NOYES and P. K. PORTER. Checked by H. T. CLARKE and J. H. BISHOP.
IN a 5-l. round-bottom flask (Pyrex) is placed a mixture of 500 g. of phthalic anhydride and 400 g. of 28 per cent ammonium hydroxide. The flask is fitted with an air condenser not less than 10 mm. in diameter and is then slowly heated with a free flame until the mixture is in a state of quiet fusion at a temperature of about 300'0. It requires about one hour before all the water has gone and about one and a half to two hours before the temperature of the reaction mixture reaches 300'0 and the mixture is a homogeneous melt. It is advisable, during the heating, to shake the flask occasionally; some material sublimes into the condenser and must be pushed down with a glass rod. The hot reaction mixture is now poured out into a crock, covered with a paper to prevent loss by sublimation, and allowed to cool. The product is practically pure without further treatment, and melts at 232-235'0. The yield is 470-480 g. (94-95 per cent of the theoretical amount).
Phthalimide may also be made by using 500 g. of phthalic anhydride and 500 g. of ammonium carbonate which has been previously ground in a mortar. The subsequent procedure is the same as when aqueous ammonia is used. Frequent shaking is necessary, and the sublimed material must be occasionally pushed back into the reaction flask. About two hours are required for completion.
Several smaller runs of 25 g. of phthalic anhydride gave the same percentage yield.
Phthalimide may be recrystallized from water, but only about 4 g. of phthalimide will dissolve in a liter of boiling water. It may also be crystallized from alcohol, in which solvent it dissolves to the extent of five parts in a hundred at boiling temperature.
On a large scale, it would be advisable to collect the small amount of ammonia given off during the reaction.
If desired, the product obtained by pouring the reaction mass into the crock may be treated with hot water to soften the cake, broken up with a glass rod, transferred to a flask and boiled with water for a few minutes. This treatment, however, is quite unnecessary; for all practical purposes, the crude cake, as it is obtained, may be ground up and used directly.
3. Other Methods of Preparation
Phthalimide has been formed by heating ammonium phthalate; by heating acid ammonium phthalate; by passing dry ammonia over heated phthalic anhydride; by treating phthalyl chloride with dry ammonia; by heating phthalamide; by heating phthalic anhydride with ammonium thiocyanate; by heating phthalic anhydride with urea; by heating phthalic anhydride with ammonium carbonate;[1b] by heating phthalic acid with nitriles;[2b] by fusing o-cyanobenzoic acid;[3b] and by the action of potash on o-cyanobenzaldehyde.[4b]
 Jahresb. 1868, 549; Ann. 19, 47 (1836); 41, 110 (1842); 42, 220 (1842); 205, 300 (1880); 215, 181 (1882).
 Jahresb. 1847-1848, 590.
 Am. Chem. J. 3, 29 (1881).
 Am. Chem. J. 3, 28 (1881).
 Ber. 39, 2278 (1906).
 Ber. 19, 1398 (1886),
 Ber. 10, 1166 (1877); Am. Chem. J. 18, 333 (1896); J. Am. Chem. Soc. 32, 116 (1910); Z. angew. Chem. 32, I, 301 (1919).
[1b] J. Am. Chem. Soc. 42, 1282 (1920).
[2b] J Am. Chem. Soc. 18, 680 (1896); 20, 654 (1898).
[3b] Rec. trav. chim. (I) 11, 93 (1892).
[4b] Ber. 30, 1698 (1897).
Of these, the first three are the only ones which need be considered as methods for the preparation of phthalimide. It was found that the third was by no means easy to bring about: dry phthalic anhydride is apparently only superficially affected by the dry ammonia, and it was difficult to introduce sufficient heat into the loose mass of crystals to cause the reaction to start.
/ / C3H5(OH)3 + C6H5NH2 + 4O(C6H5NO2) > + 4H2O /
Prepared by H. T. CLARKE and ANNE W. DAVIS. Checked by ROGER ADAMS and A. W. SLOAN.
IN a 5-l. round-bottom flask, fitted with an efficient reflux condenser of wide bore, are placed, in the following order, 80 g. of powdered crystalline ferrous sulfate, 865 g. of glycerol (c. p.), 218 g. of aniline, 170 g. of nitrobenzene, and 400 cc. of concentrated sulfuric acid (sp. gr. 1.84). The contents of the flask are well mixed and the mixture heated gently over a free flame. As soon as the liquid begins to boil, the flame is removed, since the heat evolved by the reaction is sufficient to keep the mixture boiling for one-half to one hour. If the reaction proceeds too violently at the beginning, the reflux condenser may be assisted by placing a wet towel over the upper part of the flask. When the boiling has ceased the heat is again applied and the mixture boiled for five hours. It is then allowed to cool to about 100'0 and transferred to a 12-l. flask; the 5-l. flask is rinsed out with a small quantity-of water. The 12-l. flask is then connected with the steam-distillation apparatus shown in Fig. 3, a 12-l. flask being used as a receiver; steam is passed in (without external heat) until 1500 cc. have distilled (ten to thirty minutes). This removes all the unchanged nitrobenzene (10-20 cc.). The current of steam is then interrupted, the receiver is changed, and 1500 g. of 40 per cent sodium hydroxide solution are added cautiously through the steam inlet. The heat of neutralization is sufficient to cause the liquids to boil and thus become thoroughly mixed. Steam is then passed in as rapidly as possible until all the quinoline has distilled. In this process, 6-8 l. of distillate are collected (two and a half to three and a half hours are required, unless a very efficient condensing apparatus is used, under which conditions the distillation may be complete in one-half to one and a half hours). The distillate is allowed to cool, and the crude quinoline separated. The aqueous layer of the distillate is again distilled with steam until all the quinoline has been volatilized and collected in about 3 l. of distillate.
These 3 l. of distillate are then mixed with the first yield of quinoline and 280 g. (150 cc.) of concentrated sulfuric acid are added. The solution is cooled to 0-5'0, and a saturated solution of sodium nitrite added until a distinct excess of nitrous acid is present (as shown either by starch-potassium iodide paper or by the odor). This generally requires 50 to 70 g. of sodium nitrite. The mixture is then warmed on a steam bath for an hour, or until active evolution of gas ceases, and is then distilled with steam until all the volatile material has been expelled (41. of distillate will result) The receiver is then changed and the mixture in the distillation flask is neutralized, as before, with 700 g. of 40 per cent sodium hydroxide solution. The quinoline is distilled exactly as described above, the aqueous portions of the distillate being distilled with steam until all the quinoline has been isolated. The crude product is then distilled under reduced pressure, and the fraction which boils at 110-114'0/14 mm. is collected. The foreruns are separated from any water which may be present, dried with a little solid alkali, and redistilled. The total yield is 255-275 g. (84-91 per cent of the theoretical amount based on the aniline taken).
Although these directions have been used many times with results exactly as described, in a few cases the yields have dropped to 60-65 per cent without any apparent reason. At present no explanation can be given for this.
In the Skraup synthesis of quinoline the principal difficulty has always been the violence with which the reaction generally takes place; it occasionally proceeds relatively smoothly, but in the majority of cases gets beyond control, with consequent loss of material through the condenser. By the addition of ferrous sulfate, which undoubtedly functions as an oxygen carrier, the reaction is extended over a longer period of time. It is thus possible to work with much larger quantities of material when ferrous sulfate is employed.
It is important that the materials should be added in the correct order; should the sulfuric acid be added before the ferrous sulfate, the reaction may start at once. It is also important to mix the materials well before applying heat; the aniline sulfate should have dissolved almost completely and the ferrous sulfate should be distributed throughout the solution. To avoid danger of overheating, it is well to apply the flame away from the center of the flask where any solids would be liable to congregate.
In the apparatus for steam distillation, the greater portion of the condensation is effected by the stream of water passing over the receiver. It is, therefore, necessary that the stream passing through the condenser should be sufficiently rapid to cause it to form a uniform film over the receiving flask. A 12-l. flask is even more efficient as a condenser than the 5-l. flask. It is important that the tube through which the vapors leave the distillation flask should be neither too short nor, especially, too narrow. Where the external diameter of the steam inlet tube is 5-8 mm., the internal diameter of this steam head should be not less than 28 mm. Were it less, the current of steam passing through it would be so rapid as to prevent small quantities of liquid from returning to the flask, and these would be driven over into the receiver.
Much time can be saved by the use of the steam distillation apparatus described, especially when large quantities have to be handled. The above directions avoid the use of extraction methods, which not only consume more time but may lead to appreciable losses of material. If the downward condenser is of iron, the apparatus is even more efficient and the time for the steam distillation is halved.
The percentage yields have been based on the amount of aniline taken. It would probably be more legitimate to base the calculation on the amounts of aniline taken and of nitrobenzene not recovered, since undoubtedly the latter is reduced to aniline during the course of the reaction. If this be done, the yield is found to be only 55 to 60 per cent of the calculated amount.
In a number of experiments, the glycerol used contained an appreciable amount of water. Under these conditions, the yield of product is much lower. "Dynamite" glycerol containing less than half a per cent of water is best employed; U. S. P. glycerol contains 5 per cent of water and usually gives lower yields.
3. Other Methods of Preparation
Quinoline has been produced by passing the vapor of allylaniline over red-hot lead oxide;[1a] by heating acrylideneaniline, or better, a mixture of aniline, glycerol and sulfuric acid;[2a] by heating aniline with glycerol and sulfuric acid, using nitrobenzene as an oxidizing agent; by treating a mixture of glyoxal and o-toluidine with alkali; by treating a solution of o-aminobenzaldehyde with acetaldehyde and alkali; by heating methylacetanilide with zinc chloride; by heating aminoazobenzene with glycerol and sulfuric acid; by heating a mixture of aniline, glycerol and sulfuric acid with arsenic acid.
[1a] Ber. 12, 453 (1879).
[2a] Ber. 13, 911 (1880); Monatsh. 1, 316 (1880).
 Monatsh. 2, 141 (1881); J. prakt. Chem. (2) 49, 549 (1894),
 Monatsh. 15, 277 (1894).
 Ber. 15, 2574 (1882); 16, 1833 (1883).
 Ber. 23, 1903 (1890).
 Ber. 24, 2623 (1891)
 Ber. 29, 704 (1896)
Of the above methods, the only ones which need be considered are those in which a mixture of aniline, glycerol and sulfuric acid is heated with an oxidizing agent. With the use of nitrobenzene, the reaction, according to the original method, takes place with extreme violence.
The method above described is the most satisfactory for the preparation of quinoline itself, but for the preparation of homologues of quinoline, the use of arsenic acid is preferable, since the yields are somewhat greater.
Since the work was carried out, a method has been published in which aniline, glycerol and sulfuric acid are treated with ferric oxide. By this method Adams and Parks were unable to obtain yields comparable with those resulting from the above directions.
 Chem. News 121, 205 (1920).
(1)HOC6H4OH(4) + O(Na2Cr2O7 + H2SO4)—> OC6H4O + H2O Prepared by E. B. VLIET. Checked by ROGER ADAMS and E. E. DREGER.
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).
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. 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, hydroquinone, benzidine, p-phenylenediamine, sulfanilic acid, p-phenolsulfonic acid, arbutin, aniline black, and the leaves of various plants. Quinone is also formed by several other methods: by the fermentation of fresh grass; by the action of iodine on the lead salt of hydroquinone;[1b] by the decomposition of the compound, C6H42CrO2Cl 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]
 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).
 Ann. 27, 268 (1838).
 Ann. 51, 152 (1844) j Am. Chem. J. 14, 555 (1892).
 Jahresb. 1863, 415.
5 Jahresb. 1863, 422.
6 Ann. 159, 7 (1871); Ber. 8, 760 (1875).
 Ber. 8, 760 (1875).
 Ann. 107, 233 (1858).
 Ber. 10, 1934 (1877); 34, 1285 (1901).
 Ann. 89, 247 (1854); Ber. 34, 1162 (1901).
 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).
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.
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 CH3C6H4SO2Na2H2O. 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.
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, zinc dust in alcohol or water, sodium sulfite, sodium sulfide, potassium hydrosulfide (the thio acid being first formed) and sodium arsenite. (2) From toluene by the Friedel and Crafts reaction, using either sulfur dioxide and hydrogen chloride or sulfuryl chloride. (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]
 Ann. 142, 93 (1867).
 Ber. 9, 1586 (1876).
 Ber. 3, 965 (1870).
 D. R. P. 224,019; Chem. Zentr. 1910, (II), 513.
 Ber. 42, 3821 (1909).
 Ber. 41, 3351 (1908); Ber. 42, 480 (1909).
 Ber. 41, 3318 (1908); J. Chem. Soc. 93, 754 (1908).
 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).
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.
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; by heating 2,4,6-trinitrotoluene with fuming nitric acid in a sealed tube at 180'0 for three hours; by heating 2,4,6-trinitrobenzoic acid or its sodium salt with water, alcohol, dilute sodium carbonate or other suitable solvent.
 Ber. 9, 402 (1876); Ann. 215, 344 (1882).
 Ber. 16, 1596 (1883).
 D. R. P. 77,353; Frdl. 4, 34 (1894).
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.
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).
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; 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; this method has been found to be difficult to control on a laboratory scale.
[1a] Ber. 3, 223 (1870)
 D. R. P. 77,559; Frdl. 4, 34 (1894)
 D. R. P. 226,225; Frdl. 10, 167 (1910).
The method described above is a modification of a patented process, in which trinitrotoluene suspended in sulfuric acid is treated with chromic anhydride.
 D. R. P. 127,325; Frdl. 6, 148 (1901).
Acetic acid, 18, 33, 64 Acetone, 41 Acetophenone, 1 Ammonium carbonate, 75 Ammonium hydroxide, 37, 75 Aniline, 71, 79 Anthranilic acid, 47
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
Carbon tetrachloride, 23 Chlorine, 37 Copper sulfate, 38
Dibenzyl ether, 6 a, g-Dichloroacetone, 13-15 Dimethylaminobenzaldehyde, 17-21 Dimethylaniline, 17, 47
Ethyl alcohol, 23, 27 Ethyl oxalate, 23-26 Ethyl phenylacetate, 27-28
Ferrous sulfate, 79 Formaldehyde, 17
Gelatine solution, 37 Glycerol, 29, 33, 79 Glycerol a, g-dichlorohydrin, 29-31 Glycerol a-monochlorohydrin, 33-35
Hydrazine sulfate, 37 40 Hydrochloric acid, 17, 30, 34, 47, 71 Hydroquinone, 85
Mesitylene, 41-45 Methyl red, 47-61
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
Oxalic acid, 23
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