Part 2

The analogous derivatives of the meta toluene sulphonic acid with one or two exceptions have not been made or studied, nor has the acid itself been prepared in a form which could be recognized. The following derivatives of meta toluene sulphonic acid have been made and studied; the amide by Müller, Pechmann, Pagel, Beckurts, F.H.S. Muller, Nevile and Winther, Chase Palmer, Klason, Valin, Noyes and Walker, Metcalf, and Griffin; meta sulphamine benzoic acid by Limpricht and Uslar, and Griffin; meta toluene sulphon anilide and toluide by Muller and Wiesinger, (Ber. d. chem. Ges, 12,1348), and by Griffin; the latter also made and studied several metallic salts.

The literature on the ortho and para toluene sulphonic acids and their derivatives is voluminous, and covers a great many derivatives which have been thoroughly studied and whose structure has been determined. The literature on meta toluene sulphonic acid is very meagre, comparatively, and all that could be found is mentioned in this paper. This would seem to indicate that investigators have avoided this series, and apparently the reason is due to the difficulties encountered in isolating the free acid.

THEORETICAL DISCUSSION

The object of this paper is to prepare a solution of meta toluene sulphonic acid, as probably obtained by Griffin, by the most promising of the investigated methods and to find an acceptable one for isolating the acid in the solid state. After a solution is obtained similar to that found by Griffin, (loc. cit.), the intention is to remove as much water as possible by distillation under diminished pressure and then to precipitate the acid by the method of Kastle, (Amer. Chem. J., Vol. 44, page 483), namely saturate the remaining solution with gaseous hydrochloric acid. It is hoped that in this way the solid acid may be obtained which can then be studied.

As has been proved by previous experimenters and discussed above, no direct method of sulphonating toluene will give any of the meta sulphonic acid. Therefore to get a compound containing a methyl group with a sulphonic acid group in the position meta to it some compound with these already in that position and containing some other group which can be replaced by hydrogen might be used, i.e. a disubstituted toluene. The two groups which can be readily replaced by hydrogen are the amino group and bromine, the former by the diazo reaction and the latter by treatment with metallic sodium; the easier of the two to prepare and replace is the amino group and this is the one made use of in this synthesis. This replacement has been widely studied (Amer. Chem. J., by Palmer 8, 243; Orndorff 9, 387; Graham 11, 319; Dashiell 15, 124; Metcalf 15, 301; Parks 15, 320; Shober 15, 379; Beeson 16, 244; and Dissertations by Weida, Cameron, and Chamberlain, all 1894.), and the various conditions affecting it determined. The foregoing investigators decomposed their diazo compounds with alcohols sometimes using certain substances to cause the alkoxy or hydrogen reactions to take place. Later investigators (Buchka, Berichte 23, 1628, St. Von Niemantowski, Ibid., 34, 3325 (1901), Ullman and Bieleck, Ibid., 34, 2174, and Bigelow, J. Amer. Chem. Soc., Vol. 41, 1566), have shown that this decomposition is greatly increased by the presence of copper powder. As the first method has been more extensively studied it was adopted in this case.

The action of methyl, ethyl, and n-propyl alcohols on diazo compounds has been well studied by the above authors, and it has been shown that the first two at ordinary pressures give the alkoxy reaction either in whole or in part; n-propyl alcohol gives the hydrogen reaction only. Also the first two give the hydrogen reaction in the presence of zinc dust or sodium carbonate, but in these cases form salts of the acid. On account of its rarity n-propyl alcohol was not used, but n-butyl alcohol which is available in large quantities and in a pure condition was employed. Recent advances in fermentation as applied to organic chemistry have made this substance easily obtainable as a byproduct in the production of acetone which was needed in large amounts during the late war. Its use was found to be successful; it boils at 117 and so can be easily distilled off after decomposition has been effected without a great increase in temperature above the boiling point of water, which increase Griffin (loc. cit.) showed to cause carbonization. For this reason i-amyl alcohol although available was not considered,--also higher alcohols because of this fact and because of their rarity.

Of the four amino toluene sulphonic acids theoretically possible in which the sulphonic acid group is in the meta position in reference to the methyl group only two are commonly known, No. 1, and No. 2.

CH{3} CH{3} CH{3} CH{3} / \ / \ / \ / \ / \ / \ / \ / \ / \NH{2} / \ / \NH{2} / \ | | | | | | | | | | | | | | | | HSO{3} \ / \ / HSO{3} \ / NH{2} \ / HSO{3} \ / \ / \ / \ / \ / \ / \ / \ / NH_{2}

Methods of preparing No. 1 and No. 2 were found but without details, so a method had to be worked out to obtain them easily and in good yield. After a little experimenting No. 1, or ortho toluidine sulphonic acid was readily obtained in good yield and in a fairly pure condition. No. 2, or para toluidine meta sulphonic acid was obtained in only a ten per cent yield and by means of a much more difficult method of procedure. The preparation of this acid was undertaken first and consumed a long time; Griffin did his work starting with this acid and I hoped to get as far as he did earlier. It was then available in the market as was the ortho toluidine sulphonic acid, but now neither are available.

The methods employed by earlier investigators when they wished to isolate their diazo compounds was to suspend the substance to be diazotized in alcohol, and then pass in nitrous fumes generated by dropping concentrated nitric acid onto arsenious oxide. The diazo compound from ortho toluidine sulphonic acid is so nearly insoluble in water that it was found possible to diazotize it in water suspension, and generate the nitrous fumes in the solution itself by adding a solution of sodium nitrite to the water suspension containing hydrochloric acid. After a short time the diazo compound separates out and can be filtered off, washed and dried. It is a very stable substance as compared with other diazo compounds. This method was worked out, there being no mention of it in the literature.

SULPHONATION OF ORTHO TOLUIDINE

Of the possible sulphonic acids of ortho toluidine the commercial product of former days was the one in which the sulphonic acid group was in the para position to the amino group, and meta to the methyl group; thus this acid could find use in preparing the toluene meta sulphonic acid if a method of replacing the amino group by hydrogen could be found. This acid is not now on the market in America because of its limited use in dyestuffs. It is mentioned in Schultz and Julius, (“Farbestoff Tabellen”, 1894 Edition, Trans. by F. C. Green), Cain, (“The Manufacture of Intermediate Products for Dyes”) and Nevile and Winther, (Ber. d. chem. Ges. 13, 1940.), which latter give a method of preparation which was used industrially,--the baking of ortho toluidine sulphate. Their description is rather indefinite but after a few preliminary trials a suitable method was found. I will describe all the experiments attempted, and include the one finally adopted. The ortho toluidine used was (“Practical.”) obtained from Eastman Kodak Co.

Experiment 1.

Ortho toluidine was suspended in water and conc. sulphuric acid added with vigorous stirring until all the amine had dissolved. The solution was heated to boiling until the sulphate had dissolved, and then cooled and the crystals thus obtained filtered off and dried. This was then powdered and ground with some powdered oxalic acid. These mixtures with and without oxalic acid were then baked until a sample was completely soluble in sodium hydroxide. The mass had become a deep grayish purple. It dissolved in water to give a deep red solution. Nothing satisfactory was obtained from any of these bakes, the formation of a red dyestuff as mentioned by Nevile and Winther seeming to be formed in a great quantity and very easily. Hence this method was discarded.

Experiment 2.

In this case an excess of sulphuric acid was used. After the oxalic acid had all been decomposed or driven off the mass turned black and became very pitchy. Nothing could be done with it so it was thrown away.

Experiment 3.

In this case an excess of ortho toluidine was used. The red dyestuff was formed in great amount and very easily. The temperature was kept below 195 to lose none of the toluidine which boiled at 199.

Experiment 4.

This method gave the best results and is the one employed in the preparation of all the material used in the thesis. Equal weights of ortho toluidine and sulphuric acid (100gms. of each were used; 100gms. of ortho toluidine is 108cc., and 100gms. of sulphuric acid (s. g. 1.84) are 56cc.), were mixed and baked at 190-195 until a sample would dissolve in ten per cent sodium hydroxide solution to give a clear solution; this took one and a half hours. The mixture at first melts in the solution of the sulphate and sulphuric acid formed by the heat of combination; as heating is continued it gradually becomes solid and finally very hard; it has become gray in color. When it is perfectly dry a test is made to see if it dissolves in sodium hydroxide giving a clear solution. If so, sulphonation is complete. By using an oven with a glass door the reaction mixture can be watched and the completion of the baking observed. However the test for complete solubility should always be made. The addition of powdered oxalic acid to the reaction mixture did not seem to be of advantage, because no visible reaction commenced until this had been driven off or decomposed. It is usually added in producing sulphonic acids by baking the sulphates of the amines to increase the porosity of the mass and thus facilitate removal of the product. However here the only effect seemed to be to retard the reaction, as the product was the sane hard grayish mass as without the acid, and it was just as difficult to dig it out. It took an hour longer to complete the reaction with the addition of the oxalic acid.

The best results were obtained when the temperature of the oven was kept at 193, although five degrees variation did not appreciably affect the product. A lower temperature gives little or no action, while a higher one drives off the ortho toluidine and also seems to favor the formation of the red dyestuff.

As stated above, complete sulphonation is shown by the solubility of the acid in ten per cent sodium hydroxide solution. If any unchanged amine is present as sulphate the solution will become milky due to liberation of the insoluble amine. On boiling a solution of the acid a slight hydrolysis takes place so that the smell of ortho toluidine is present, yet the solution is always perfectly clear.

The product or “bake” appears as a hard grayish mass, slightly porous. It is dug out, pulverized, boiled up in a large evaporating dish, containing water and a little (10cc.) hydrochloric acid, with animal charcoal and filtered. The solution should be almost colorless. The effect of the slight amount of hydrochloric acid was accidental; the first solutions were always a deep red color due to some of the red dyestuff seeming to be present, and the longer the solution was boiled the redder it got. A little acid seems to prevent this entirely. The solution is evaporated on a water bath until a scum has formed on the surface when it is allowed to cool and crystallize. It crystallizes in small almost white needles, which appear to fill the entire liquid; this is deceptive as on filtering the bulk is considerably reduced. They fall to a powder when they are dry. If they are colored red or pink they are washed while still on the filter with water; alcohol does not remove this color.

The acid as formed has no melting point, but chars and decomposes on heating. A sample was tested for nitrogen and sulphur with very good positive results. On fusion with caustic soda and acidification of the product a positive reaction was obtained on the addition of bromine water as is customary with phenols.

It was identified as identical with the acid of Nevile and Winther (loc. cit.) by conversion thru the diazo compound into dinitro ortho cresol, melting at 85.8 as described under the description of the diazo compound.

SULPHONATION OF PARA TOLUIDINE

Metcalf, (loc. cit.), gives a method for the preparation of the sulphonic acids of para toluidine, and states that both the possible acids are formed, with the meta position (referred to the methyl group) in good yield. Schultz and Julius, (“Farbestoff Tabellen”, 1894 Edition, Trans, by F. C. Green), and Nevile and Winther, (loc. cit.), say that the sulphonation of para toluidine gives a mixture of the sulphonic acids, with the ortho (referred to the methyl group) sulphonic acid in a much greater yield. As the sulphonation of para nitro toluene gives (Dissertation, R. S. Norris, BPL. 5976.109) a ninety-five per cent yield of the ortho sulphonic acid, it would seem as though the amino compound should give a large yield of the acid (sulphonic acid group ortho to the methyl group,) and such was found to be the case.

I followed Metcalf’s directions as follows: in an apparatus fitted with an automatic stirrer and a thermometer I placed 200 grams (110cc.) of twenty per cent fuming sulphuric acid. I then slowly added with rapid stirring 100grams of powdered para toluidine which was obtained from the Newport Chemical Works. The addition took thirteen minutes. The initial temperature of the solution was 18°C. The maximum was obtained when about half the toluidine had been added and was 148°C. The final temperature was 130°C. After addition was complete I stirred for five minutes, and then slowly heated the mixture to 180°C. and kept it there for an hour. Sulphonation was then complete. I then poured it into an equal volume of cold water (220cc.) in an evaporating dish and allowed it to stand over night. The next day the dish seemed filled with grayish crystals; these were filtered off. The solution was allowed to stand for four weeks with no results. (Metcalf says that the disulphonic acid separated in three weeks from his solution.)