Part 3

I dissolved the crude acid obtained as above in ten liters of water (Metcalf’s directions) and precipitated the excess of sulphuric acid with barium hydroxide, and then filtered the solution. It was a clear brownish color. I then evaporated to 100cc. A smell of para toluidine was always present in the vapor indicating a probable hydrolysis of the acid. (Nevile and Winther (loc. cit.) say that this sulphonic acid can be hydrolyzed by heating with water), A test after sulphonation and before evaporation showed a sample to be completely soluble in water, and no cloudiness was produced when a sample was dissolved in sodium hydroxide, as is the case if a solution of para toluidine sulphate is dissolved in the same reagent. When the volume had reached 100cc. a light brown crust had formed on top of the liquid and on cooling and filtering two products were obtained; a light brown powdery substance in larger amount (47.5 grams.), and a small amount of hard square brown crystals. On evaporating the filtrate nearly to dryness more material separated which did not look like either of the above substances; it weighed twenty grams. This has not been investigated as yet.

As the brownish powdery substance was mixed with the flat crystals produced above, a method had to be found to separate them and purify each. I screened them as much as possible with good results. I removed the last of the fine powder by dissolving it off with hot water. Metcalf said that they could be separated by their difference in specific gravity in fifty per cent alcohol but this method was unsuccessful. I boiled up the aqueous solution of the powdery substance with animal charcoal, filtered and evaporated to crystallization. Square, flat, white crystals were obtained identical in all but color with those mentioned above. They are soluble with difficulty in cold water, readily in hot, and insoluble in alcohol. In these properties and in appearance they compare to the ortho sulphonic acid of para toluidine as made and described by Parks, (Dissertation, 1892). Metcalf and Nevile and Winther say that the meta sulphonic acid of para toluidine forms needles, but I obtained nothing that could in any way be called needles. This sulphonic acid had no melting point, but charred and decomposed. A test for elements showed nitrogen and sulphur to be present. The aqueous solution had a strong acid reaction to litmus.

In order to see if this might be the desired acid I tried to prepare an acid chloride with phosphorus pentachloride in the usual way, and then intended to convert it into the amide and get a melting point for identification. I used equal weights of the acid and phosphorus pentachloride. I ground them together at ordinary temperature in a mortar: no result. I heated it on a water bath: no result. I heated it on a gauze over a flame: no result except decomposition and carbonization. However I poured water into the mixture and decomposed the excess of phosphorus pentachloride, and filtered. A gummy brownish mass remained which was insoluble in all reagents tried, (methyl and ethyl alcohol, benzine, petroleum ether, (40-60), water, carbon tetrachloride, dilute hydrochloric acid, acetone, and acetic acid.) Ethyl ether extracted a very small amount, just enough to color it yellow, and leave a yellow color on porcelain on evaporation, but not enough to make a study of the properties. On shaking up with concentrated ammonia the mass became very finely divided, but no solution appeared to take place; on filtering and evaporating to dryness there was no residue.

The material mentioned above as being the final product from the sulphonation of para toluidine, obtained in a yield of twenty grams or ten per cent yield and then uninvestigated, has since been identified as the acid I was looking for, or para toluidine meta sulphonic acid. A small amount was cooled and diazotized in the usual manner; the diazo compound seemed to be insoluble in the amount of water used, for a white crystalline needle-like precipitate appeared. This was decomposed by boiling with dilute nitric acid (Nevile and Winther, loc. cit.), and on cooling small tufts of yellow needles separated. These were filtered off and dried, then recrystallized from alcohol. The best portions of these were then recrystallized from ether and the melting point determined. They melted at 79.5-79.8 (uncorr.). Nevile and Winther gave 79-80, showing that they did not purify their compound. The product is dinitro para cresol, or 3-nitro, 4-hydroxy, 5-nitro toluene.

DIAZOTIZATION OF ORTHO TOLUIDINE SULPHONIC ACID.

Nevile and Winther (loc. cit.), stated that they obtained a diazo compound from their ortho toluidine sulphonic acid and described a few properties, but gave no details of manipulation, so I made several trials to determine the best acceptable method.

Experiment 1.

I suspended some ortho toluidine sulphonic acid in denatured alcohol, and passed in a rapid current of nitrous fumes, generated by dropping concentrated nitric acid into a saturated solution of sodium nitrite, for fifteen minutes. The suspension became slightly warm, and rather pasty at the end. I allowed it to stand a half hour, and at the end of that time it had become very thick and pasty. I then filtered it off by suction, washed with ether, and dried.

Experiment 2.

The procedure used was the same as above using ethyl alcohol in place of denatured alcohol, but for some reason no diazotization appeared to take place. The acid was filtered off and used again.

Experiment 3.

A saturated water solution of the acid was made by boiling some of it up with water, cooling and filtering. No precipitate appeared on passing in nitrous fumes.

Experiment 4.

Some of the acid was dissolved in sodium carbonate solution, sodium nitrite solution added, and after cooling, concentrated hydrochloric acid added drop by drop. Nitrous fumes were given off, but no precipitate appeared.

Experiment 5.

This seems to be the best method and the one employed hereafter in the preparation of all the material subsequently used. The solid ortho toluidine sulphonic acid is suspended in concentrated hydrochloric acid and vigorously stirred. The solution becomes warm and the crystals change in appearance, probably due to the formation of the hydrochloride. The mass is then cooled to 5°, and sodium nitrite solution added slowly with stirring. Immediate reaction takes place, and the mass becomes very pasty as in the first experiment. After obtaining a reaction with starch iodide paper the mixture was allowed to stand a half hour, then filtered by suction, washed with ether and dried. In appearance it was identical with the diazo compound obtained in experiment 1, and can be kept in the same way.

That it was a diazo compound was shown as follows: It was spotted on a piece of filter paper with an alkaline solution of H acid--a red coloration indicates the formation of a red azo dyestuff.

Some of the diazo compound was boiled with dilute nitric acid as described by Nevile and Winther, and a yellowish precipitate of needles obtained, which on recrystallization from denatured alcohol gave light yellow needles of dinitro ortho cresol, (3-hydroxy 3,5-dinitro toluene), melting at 83.5-84° uncorr. (Nevile and Winther gave 85° for the pure substance.) This dinitro compound was obtained in nearly quantitative yield indicating that the diazo compound was presumably pure.

PHYSICAL PROPERTIES OF THE DIAZO COMPOUND

It is almost insoluble in water, and is insoluble in denatured alcohol and ether.

It is a white solid which can be dried and kept without apparent decomposition; it gradually turns pink when exposed to the light for several days, so is kept in a brown bottle if not required for immediate use. It does not explode when struck with a hammer, but deflagrates violently if a flame is brought near or if heated on porcelain.

DECOMPOSITION OF THE DIAZO COMPOUND

(1) With n-Butyl alcohol in the presence of sodium carbonate.

A portion of the dry diazo compound was placed in a flask connected with a reflux condenser, and solid sodium carbonate and n-butyl alcohol added. No reaction took place at ordinary temperature so heat was applied. Decomposition started at 65° and evolution of hydrogen proceeded evenly and smoothly until all the diazo compound had disappeared. The alcohol, at first colorless, became an orange and finally a brown color. The solution was then refluxed an hour to ensure complete decomposition of the diazo compound. The smell of an aldehyde was evident indicating that the hydrogen reaction was taking place; the solution was tested with Schiff’s reagent and with ammoniacal silver nitrate with distinct positive results in both cases, showing aldehyde was present. The alcoholic solution was filtered from the sodium carbonate remaining, and the alcohol distilled off on an oil bath. A yellowish-orange porous solid was left in such a small amount that no derivatives could be made and studied. It was free from the diazo compound, shown by its giving no color with an alkaline solution of H acid.

(2) With n-Butyl Alcohol alone.

The previous experiment showed that n-butyl alcohol would decompose the diazo compound in the presence of sodium carbonate and replace the amino group by hydrogen, so this time a decomposition with the alcohol alone was tried. Decomposition took place evenly and smoothly as before at the same temperature, and the solution became a clear brownish-orange. Aldehyde was given off and tested for as before with positive results. The alcohol was removed by distillation and a thick brownish syrupy liquid was left. This was easily soluble in water, so was dissolved, filtered, and the solution used in the following experiments. At this point it is similar in every way to the solution obtained by Griffin (loc. cit.) from the diazo compound of para toluidine meta sulphonic acid.

Subsequent preparations of this syrup were made in the above way with similar results in every case. The only precaution to be observed is that no part of the flask containing the reaction mixture be allowed to become too hot as the diazo compound is then decomposed violently leaving a grayish ash.

A STUDY OF THE SOLUTION OBTAINED BY THE DECOMPOSITION OF THE DIAZO COMPOUND