VII. The Action of Phenols upon the Symmetrical Chloride of Paranitroorthosulphobenzoic Acid.

Remsen and Saunders[18] in their investigation of the chlorides of orthosulphobenzoic acid, studied the action of phenol upon these substances, and from both the symmetrical chloride and the mixed chlorides, they obtained a normal diphenyl ether together with a red substance which was not further studied. It was formed in small quantity and was probably the corresponding sulphonphthalein. Later McKee[19] obtained these same substances from both the symmetrical and the unsymmetrical chlorides. R. Meyer[20] obtained analogous substances by the action of various phenols upon phthalyl chloride. It seemed probable, therefore, that the chlorides of paranitroorthosulphobenzoic acid would yield similar derivatives, and a study was accordingly made of the reaction of the symmetrical chloride with a series of phenols. The products in some instances were exceedingly difficult to deal with, possessing properties that made it impossible to prepare them for analysis, but even in such cases there could be little doubt as to the general nature of the reactions which had occurred.

1.The Action of Phenol upon the Symmetrical Chloride of Paranitroorthosulphobenzoic Acid.

A portion of the symmetrical chloride was brought together with somewhat more than double the molecular amount of phenol. The mixture was placed in a good-sized test-tube and the temperature gradually raised by means of a sulphuric acid bath.

As soon as the phenol melts, some slight action occurs, as is indicated by the fact that the mixture assumes a bright red color. No appreciable amount of hydrochloric acid gas is evolved however, until the liquid mixture has reached a temperature of about 115°. At this point the gas is freely evolved, and the action is complete at a temperature of 125°. The temperature observations were made by means of a thermometer used as a stirring rod in the mixture. During the heating, the color of the liquid becomes a much more intense red, growing darker in shade, and the liquid itself becomes somewhat viscous but does not solidify while hot.

When cool, the melt was repeatedly extracted with boiling water, the aqueous solution being very deep purple in color. The colored matter was removed very slowly in this manner, and so the process was continued with dilute alkali. A solid insoluble residue was thus obtained, of a light-brownish color. This was dissolved in alcohol, boiled with boneblack and filtered. On cooling, needles of a straw yellow color were deposited from the alcoholic solution.

This proved to be the normal diphenyl etherial salt of paranitroorthosulphobenzoic acid, the formation of this substance being expressed by the equation:

COClCOOC₆H₅ // C₆H₃—SO₂Cl + 2C₆H₅OH = C₆H₃—SO₂OC₆H₅ + 2HCl. \\ NO₂NO₂

Analysis of the substance gave the following results:

I. 0.1627 gram gave 0.3398 gram CO₂ and 0.0510 gram H₂O.

II. 0.1999 gram gave 0.4180 gram CO₂ and 0.0600 gram H₂O.

III. 0.2649 gram gave 0.1561 gram BaSO₄.

Cal. for COOC₆H₅ / C₆H₃—SO₂OC₆H₅ \ NO₂ Found.

I II III

C =57.14 56.97 57.03 ——

H = 3.26 3.47 3.33 ——

S = 8.02 —— —— 8.09

This substance melts at 119° (uncorr).

It possesses properties similar to those of the diphenyl etherial salt of orthosulphobenzoic acid described by Saunders. It is insoluble in water, and is unaffected by hydrochloric acid or aqueous alkali. On heating for a short time with alcoholic potash, the needles were transformed into a voluminous precipitate. This was filtered off, dissolved in water, and hydrochloric acid was added. On cooling, characteristic crystals of the acid potassium salt of paranitroorthosulphobenzoic separated.

Analysis.

0.1392 gram lost 0.009 gram at 150° and gave 0.0385 gram K₂SO₄.

COOH / Cal. for C₆H₃—SO₂OK + H₂O \ NO₂ Found.

H₂O = 5.95 H₂O = 6.51

K = 13.65 K = 13.35

No attempt was made to isolate the corresponding intermediate chlor-etherial salt of the composition

COOC₆H₅ / C₆H₃—SO₂Cl \ NO₂

or its acid as was done by McKee[21] in his work on the analogous etherial salt of orthosulphobenzoic acid.

On evaporating the aqueous extract from the original melt almost to dryness on the water-bath, there was a deposit on the sides of thedish of scales possessing a beautiful bronze-green metallic lustre They formed a deep purple solution in alkalis, or magenta, if the solution was very dilute, and orange-yellow in acids. On acidifying the alkaline extract with hydrochloric acid, this same substance was precipitated as a brownish flocculent precipitate. It was, however, found to be impossible to obtain this substance in pure condition. The amount formed in the reaction is small, and its properties were such as to render work with it very difficult. The method of precipitation is not satisfactory because, owing to the fact that the substance is soluble in acid solutions to an unusual extent for substances of this class, the solution had to be concentrated to such a degree as to render the precipitated substance very impure from acids and alkali salts. These could not be removed by washing, obviously, without again dissolving the substance. From its properties however, and its color reactions, there can be little doubt that the substance is a sulphonphthaleïn, and that it is always formed in considerable quantities in the reaction of phenol upon the symmetrical chloride.

It was noticed that the aqueous extract of the mass left after fusion was almost always decidedly acid in reaction, and it was thought that this might be due to the formation of an acid etherial salt, whose formation would be expressed by the equations:

COClCOOC₆H₅ // C₆H₃—SO₂Cl + C₆H₅OH = C₆H₃—SO₂Cl + HCl. \\ NO₂NO₂

COOC₆H₅COOC₆H₅ // C₆H₃—SO₂Cl + H₂O = C₆H₃—SO₂OH + HCl. \\ NO₂NO₂

Accordingly, the solution was saturated with barium carbonate, the excess of carbonate removed by filtration, the filtrate concentrated, and allowed to cool. Crystals in the form of pearly scales separated, which upon analysis proved to be the neutral barium salt of paranitroorthosulphobenzoic acid.

0.2291 gram anhydrous salt gave 0.1386 gram BaSO₄.

COO / \ /Ba // Cal. for C₆H₃—SO₂O \ NO₂ Found.

Ba = 35.85 35.57

This would seen to indicate that the reaction is an incomplete one even in the presence of excess of phenol. No indications of the formation of an acid etherial salt was observed.

2. The Action of Orthocresol upon the Symmetrical Chloride of Paranitroorthosulphobenzoic Acid.

With orthocresol the reaction proceeds with more difficulty. A higher temperature was required (135°-145°), and quite an amount of tarry material was obtained from which very little could be extracted. The product was warmed repeatedly with dilute alkali, the solution so obtained neutralized with hydrochloric acid, and distilled with steam for several hours to free it from cresol. The resulting solution was then evaporated to small volume, and acidified with hydrochloric acid. A considerable precipitate was thrown down, which was easily filtered off and dried. In this condition it is a dark purple-red powder, lumps of which possessed a yellowish-bronze metallic lustre. In dilute alkaline solution it forms a deep-bluish purple solution, while in acids it is crimson, or light yellow if the solution is dilute. It is a excellent indicator, especially with ammonia.

In the insoluble tarry substance the etherial salt was sought for and obtained in small quantity only. As this substance is soluble in alcohol, and separates again on cooling in much the same condition, the etherial salt could not be isolated be crystallization from this solvent. By boiling the substance with benzene, purifying the filtrate with boneblack, and allowing the benzene to evaporate, an almost colorless gummy substance was obtained, which when dissolved in alcohol, crystallizes in small colorless needles which melt at 89°-90°. They were not obtained in quantity sufficient for analysis, but there was little doubt that they were crystals of the diorthocresol etherial salt.

Apparently much more decomposition occurred in this reaction than when paracresol was employed, probably in consequence of the higher temperature required for the reaction.

3. The Action of Paracresol upon the Symmetrical Chloride of Paranitroorthosulphobenzoic Acid.

This reaction was conducted in the same manner as with phenol. No hydrochloric acid was evolved until a temperature of about 110° was reached, although after melting, the solution had steadily darkened to a deep reddish-brown color. At 130°, after heating for several hours, hydrochloric acid ceased to be evolved. The product was treated as in the last experiment. The alkaline extract did not exhibit any marked color reactions, such as were observed in most of these experiments, being dull reddish-brown in both acid and alkaline solution.

The insoluble residue crystallized from alcohol in light brown transparent crystals, which did not lose their color by repeated crystallization, and boiling with boneblack, and melted sharply at 117°. From benzene they crystallized in colorless needles or flat, narrow plates. These become opaque on exposure to the air, apparently through loss of benzene of crystallization.

Analysis of the needles from alcohol gave the following results:

I. 0.2372 gram of substance gave 0.5137 gram CO₂ and 0.0965 gram H₂O.

II. 0.2223 gram gave 0.1203 gram BaSO₄.

Cal. for COOC₆H₄.CH₃ / C₆H₃—SO₂OC₆H₄.CH₃ \ NO₂ Found.

I II

C = 59.08 59.06

H = 3.98 4.52

S = 7.49 7.43

4. The Action of Hydroquinone upon the Symmetrical Chloride of Paranitroorthosulphobenzoic Acid.

Action with hydroquinone occurs at 120°-135°, the mixture at the same time becoming dark colored and viscous.

On cooling, the product was powdered and treated with dilute alkali. It readily dissolved, without residue, forming a dark red solution. In concentrated solution the addition of acid produces a voluminous precipitate, dark brown in color, which when washed, and dried in paper forms an almost black powder. A dilute solution of this powder is dark red when alkaline, orange-yellow when acid.

From the way in which this powder was obtained, and owing to the fact that its solubility prevented repeated washing, it was evident that it would not give close analytical results for a calculated formula. It was thought, however, that analysis would give a general idea of the composition.

Analysis of different specimens gave results for sulphur which averaged about 5.5%. The percentage required for the formula

C[C₆H₃(OH)₂]₂ /\ /O // C₆H₃—SO₂ \ NO₂

which represents the simplest sulphonfluoresceïn, is 7.43.

The compound could hardly have been so far from pure as to occasion such a discrepancy in results as this. It would appear, therefore, that more than two molecules of hydroquinone enter into the reaction with one molecule of the chloride. Should four molecules be involved in the reaction, leading to a compound of some such formula as

C[C₆H₃(OH)₂] /\ /O // C₆H₃—SO[C₆H₃(OH)₂]₂ \ NO₂

the theoretical percentage of sulphur would be 6.00 which corresponds much more closely with the results obtained.

This is in accord with the observations of a number of workers in this laboratory—Lyman, Gilpin, Linn and others—who have worked on various sulphonfluoresceïns, and have found that in many cases four, six and even eight phenol residues condense with one molecule of the anhydrous acid. Lyman[22] especially describes a tetra hydroquinone sulphonfluoresceïn derived from orthosulphoparatoluic acid. No etherial salt was observed.

5. The Action of Resorcin upon the Symmetrical Chloride of Paranitroorthosulphobenzoic Acid.

The reaction of resorcin with the chloride is a much cleaner one and proceeds more easily than in the case just described, leading apparently to an individual compound which is well characterized.

During the reaction, which is complete at 125°, the mixture becomes almost perfectly solid, and when cool, it is quite brittle. It was reduced to a reddish powder in a mortar and dissolved in sodium hydroxide, there being no insoluble residue. By the addition of hydrochloric acid, the sulphonfluoresceïn was thrown down as a chocolate-brown precipitate, which was filtered off, washed to neutral reaction on a filter, and dried on paper. In this condition it is a light chocolate-brown powder. In dilute alkaline solution it possesses a slight fluorescence being pink by transmitted and yellow be reflected light, suggesting eosin in a general way. It is interesting to note that the sulphonfluoresceïn of orthosulphobenzoic acid possesses a fluorescence that can hardly be distinguished from ordinary fluoresceïn and that the introduction of a nitro group into the acid residue produces much of the same effect as do the four bromine atoms in eosin. In acid solution the color is reddish-orange.

Analysis of the compound, prepared as above described, gave the following results.

COClCOOC₆H₅ // C₆H₃—SO₂Cl + 2C₆H₅OH = C₆H₃—SO₂OC₆H₅ + 2HCl. \\ NO₂NO₂

Analysis of the substance gave the following results:

I. 0.1745 gram gave 0.3339 gram of CO₂ and 0.059 gram H₂O.

II. 0.1467 gram gave 0.2820 gram CO₂ and 0.0432 gram H₂O.

III. 0.1732 gram gave 0.3345 gram CO₂ and 0.0571 gram H₂O.

IV. 0.2000 gram gave 0.1104 gram BaSO₄.

V. 0.1505 gram gave 0.0820 gram BaSO₄.

Cal. for OH / C[C₆H₃ ] /\\2 /OOH // C₆H₃—SO₂ \ NO₂ Found.

I II III IV V

C = 52.66 52.18 52.42 52.67 —— ——

H = 3.46 3.76 3.27 3.66 —— ——

S = 7.39 —— —— —— 7.57 7.48

An effort to obtain the anhydride was unsuccessful. Some loss of weight was observed, but the compound underwent decomposition before this loss amounted to much.

6. The Action of Pyrogallol upon the Symmetrical Chloride of Paranitroorthosulphobenzoic Acid.

The product of this action dissolves readily in dilute sodium hydroxide without residue, producing a very deep purple-black color when concentrated, passing to grayish-violet as the solution is diluted. On adding hydrochloric acid, precipitation occurs, as in most of these reactions. On attempting to filter off this precipitate, it forms a sticky, black mass on the filter with which little can be done. It is best to evaporate to dryness before filtration and powder the residue. This powder can then be washed fairly clean from alkali salts and acid.

Nothing to suggest the formation of an etherial salt was observed.

Analysis of this product for sulphur showed that in this galleïn, as in the case of the hydroquinone phthaleïn more than two pyrogallol residues had entered the acid residue. The indications were that six had entered into one of the chloride. This also agrees with the observation of Lyman[23], who describes a hexapyrogallol galleïn of orthosulphoparatoluic acid.

Probably a mixture of varying composition was obtained, and little importance was attached to the results save as they showed that no etherial salt is formed in the reaction.

7. The Action of β-Naphthol upon the Symmetrical Chloride of Paranitroorthosulphobenzoic Acid.

It was hoped that here, as in the case of the monohydroxy phenols an etherial salt would be obtained. It was found, however, that very little action occurred, save such as was indicated by the development of a bright carmine color in the melted mixture, until a temperature of about 160° was reached. At this point hydrochloric acid was evolved, but the chloride itself undergoes decomposition. Nothing definite could be isolated among the reaction products, save unchanged β-Naphthol.