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.
(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.