VI. The Action of Alcohols upon the Symmetrical Chloride of Paranitroorthosulphobenzoic Acid.
Reading edition
Kastle[15] found that when the chlorides of paranitroorthosulphobenzoic acid (which he supposed to be an individual) were dissolved in alcohol, and the solution boiled for some time, the acid etherial salt of paranitroorthosulphobenzoic acid was the final product. The reactions were shown to be:
COClCOOC₂H₅ // I. C₆H₃—SO₂Cl + C₂H₅OH = C₆H₃—SO₂Cl + HCl. \\ NO₂NO₂
COOC₂H₅COOC₂H₅ // II. C₆H₃—SO₂Cl + C₂H₅OH = C₆H₃—SO₂OC₂H₅ + HCl \\ NO₂NO₂
COOC₂H₅COOC₂H₅ // III. C₆H₃—SO₂OC₂H₅ + C₂H₅OH = C₆H₃—SO₂OH + (C₂H₅)₂O \\ NO₂NO₂
Kastle, it will be observed, gave the symmetrical formula to this mixture of chlorides. Several acid etherial salts were made, and a series of the neutral salts of various metals described by him.
The action of pure symmetrical chloride was studied in the same general manner to see if the resulting products would be the same as those formed from the mixed chlorides.
1. Action of Methyl Alcohol upon the Symmetrical chloride.
A portion of the chloride was dissolved in methyl alcohol, and the solution boiled until a drop added to cold water gave no precipitate, of unchanged chloride. The alcohol was then distilled off, and the thick syrup remaining, diluted with water. This solution was neutralized with barium carbonate and filtered. On cooling, the barium salt crystallized in shining mica-like plates, or in yellowish needles corresponding accurately with those described by Kastle. They gave the following analytical results.
0.2664 gram lost 0.0211 gram at 150°,
and gave 0.0870 gram BaSO₄.
Cal. for [ COOCH₃ / C₆H₃—SO₂O \ NO₂ ] 2 Ba + 3H₂O Found.
H₂O = 7.79 7.88
[anhydrous salt] Ba = 20.85 20.85
2. In like manner the barium ethyl salt was made. It also agreed perfectly with Kastle’s description, crystallizing in fine, colorless needles, forming in tufts from a not too concentrated solution. In case it is necessary to concentrate these solutions, it is of advantage to add a small quantity of alcohol to the solution as this prevents any great amount of saponification, which otherwise takes place to a noticeable extent.
Analysis.
I. 0.2824 gram lost 0.0276 gram at 180°,
and gave 0.0860 gram BaSO₄.
II. 0.2655 gram lost 0.0262 gram at 190°,
and gave 0.0815 gram BaSO₄.
Cal. for [ COOC₂H₃ / C₆H₃—SO₂O \ NO₂ ] 2 Ba + 4H₂O. Found.
I II
H₂O = 9.51 9.77 9.86
Ba = 20.00 19.84 20.02
Kastle also found that by dissolving the mixed chlorides in alcohol in the cold, and allowing the solution to evaporate, there separated after a time, crystals of the chloride of the acid etherial salt of paranitroorthosulphobenzoic acid whose formation and composition are represented in equation I.
This same product was sought for when pure symmetrical chloride was employed, but without success. In every case, crystals of unchanged chloride separated, or else it was found that it had been completely converted into the acid etherial salt. In another trial cold water was carefully added in small portions, since Kastle found that such treatment facilitated the separation of the substance; the chloride alone appeared. Still other attempts were made to obtain the substance by adding a large amount of water to the solution of the chloride in alcohol, after it had stood for some time. In this way, quite a precipitate was thrown down, and this was filtered off and crystallized from ether. It always proved to be the symmetrical chloride, and none of the other substance was obtained.
Karslake[16] in working with the symmetrical chloride of orthosulphobenzoic acid, was unable to isolate the analogous compound, although from the mixed chlorides, by the action of alcohols, Remsen and Dohme[17] had obtained chloro-etherial salts.
In as much as the pure symmetrical chloride is relatively stable in cold alcohol (it can be crystallized from warm alcohol with very little loss), it is possible that it is more stable than the chloro etherial salt, and that in consequence the latter, when formed, yields more readily to the further action of alcohol than does the unacted on chloride. Hence when the action begins, it at once proceeds to the limit. The fact that the symmetrical chloride is rather sparingly soluble in cold alcohol, making the use of concentrated solutions impossible, may also be a factor in the case. Whatever may be the cause, this substance could not be obtained under any conditions that were devised.
Having in my possession a very small specimen of crystallized unsymmetrical chloride, it was submitted to the action of ethyl alcohol, under as nearly as possible the conditions employed by Kastle. Crystals of a colorless substance were obtained, which in every respect agreed with Kastle’s description of the chloride of the acid ethyl etherial salt of paranitroorthosulphobenzoic acid. Crystallized from ether they melted at 68°.
The conditions employed by Kastle in preparing the chloride would undoubtedly lead to a relatively large proportion of unsymmetrical chloride, and it is to this chloride that the formation of the chloro etherial salt is apparently due.