C. F. H. Allen

“ 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. 24
DECOMPOSITION OF THE DIAZO COMPOUND
(1) With n-Butyl alcohol in the presence of sodium carbonate. ”

“ The methods employed by earlier investigators when they wished to isolate their diazo compounds was to suspend the 11 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. ”

“ 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, 15 yet the solution is always perfectly clear. ”

“ 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. ”

“ 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 14 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. ”

“ 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 19 a water bath: no result. I heated it on a gauze over a flame: no result except decomposition and carbonization. ”

“ He prepared para tolyl phenyl sulphone by the Friedal-Crafts reaction, para phenyl sulphone benzoic acid by oxidation of the sulphone with chromic acid, its salts, chloride, amide, and anilide, and para benzoyl diphenyl sulphone from the acid by the Friedal-Crafts reaction, and studied their reactions and properties. ”

“ 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. ”

“ 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. ”

“ 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.) ”