Study of Some Oxy Derivatives of Anthraquinone by the Potentiometric Method

L. P. Kulev and T. N. Gorizontova

The potentiometric method, as our experiments [1] have shown, makes it possible to judge the rate of lake formation depending on the nature of the mordant applied to the fabric. Since the emf arises as a result of the interaction of alizarin with the metal of the mordant, the magnitude of the emf and the time required for it to reach its maximum should also be influenced by the nature of the oxy derivative of anthraquinone. To verify this consideration, we studied a series of compounds differing from one another in the number of oxy groups and in their position in the molecule: \(\alpha\)-oxyanthraquinone, \(\beta\)-oxyanthraquinone, quinizarin, alizarin, the \(\beta\)-methyl ether of alizarin, xanthopurpurin, and purpurin.

Experimental Part

Experiments with \(\alpha\)-oxyanthraquinone

\(\alpha\)-Oxyanthraquinone was obtained from phthalic anhydride and phenol in the presence of sulfuric acid [2]. 10 g of phthalic anhydride, 8 g of phenol, and 100 ml of sulfuric acid (sp. gr. 1.84) were heated in an oil bath at a temperature of \(170^\circ\) for 2 hours. After cooling, the mass was subjected to steam distillation. The yellow crystalline precipitate of \(\alpha\)-oxyanthraquinone was recrystallized from alcohol. \(\alpha\)-Oxyanthraquinone forms needle-shaped yellow crystals, soluble in caustic alkalis with a red coloration; m.p. \(190^\circ\).

To prepare the dye paste, 1 g of \(\alpha\)-oxyanthraquinone was ground in a mortar with 9 ml of distilled water. The resulting suspension was allowed to settle, decanted from the precipitate, and placed in a hermetically sealed vessel. To 0.3 g of the finely suspended precipitate, 100 ml of distilled water was added; the solution was thoroughly stirred and placed in a thermostat, where it remained until the temperature reached \(20^\circ\)C, after which a platinum gauze electrode was immersed in the solution. Upon attainment of a constant potential difference (after 60 min), the electrode was removed, a standard sample of fabric mordanted with aluminum was wound onto it, and it was again immersed in the dye bath. The change in emf is presented by the data of Table 1.

Experiments with \(\beta\)-oxyanthraquinone

\(\beta\)-Oxyanthraquinone was obtained by fusing the silver salt

\[ \begin{array}{c} \text{[[structural formula of sodium anthraquinone sulfonate, with } \mathrm{SO_3Na}\text{ substituent]]} \end{array} \]

with calcium hydroxide hydrate [3]. 30 ml of decipro-

Table 1

[[unclear: beginning of word]] percent oleum was heated in a round-bottom flask to 130° in an oil bath; with stirring, 20 g of anthraquinone was added there. The mixture was kept for two hours at 160°, then cooled to 100° and poured into a beaker containing 500 ml of cold water. The anthraquinone that had not entered into the reaction precipitated. The solution decanted from the precipitate was heated almost to boiling and filtered. The hot filtrate was neutralized with caustic soda and cooled to room temperature, and the silver salt that separated in the form of white flakes was isolated by filtration. The yield of the silver salt was 21.8% of the theoretical.

To obtain β-oxyanthraquinone, a mixture of 17 g of the silver salt, 20 g of calcium oxide, 5 g of calcium chloride, and 150 ml of distilled water was heated in an autoclave to 150° at a pressure of 5 atm. for 4 hours [4]. The resulting orange-pink liquid mass was boiled for 1 hour with distilled water and filtered while hot. The filtrate was treated with hydrochloric acid until the red color of the solution changed to yellow. The precipitated β-oxyanthraquinone was filtered on a Büchner funnel and recrystallized from alcohol. Fine yellow crystals with m.p. 304°.

Experiments with β-oxyanthraquinone were carried out under the same conditions as with α-oxyanthraquinone.

Table 2

In terms of the magnitude of the EMF and the time required to reach its maximum, β-oxyanthraquinone displayed somewhat greater activity than α-oxyanthraquinone.

Experiments with alizarin

Commercial alizarin was purified from impurities of flavo- and anthrapurpurins by the method of Il’inskii [5]. The purified product had m.p. 283°. When mordanted fabric was immersed in a solution of alizarin, the following order of change in e.m.f. was observed.

Table 3

The maximum e.m.f. is reached here after 60 min, i.e., after the same interval of time as in the case of \(\alpha\)-oxyanthraquinone, but in magnitude it is smaller than that of the latter.

Experiments with quinizarin

Quinizarin was synthesized from phthalic anhydride and hydroquinone by the method of Rodionov, Bogoslovskii, and Fedorova [9]:

\[ \text{phthalic anhydride} + \text{hydroquinone} \ \xrightarrow[\ ]{\mathrm{H_2SO_4 + HBO_3}}\ \text{quinizarin} + \mathrm{H_2O}. \]

For the experiment a mixture was used consisting of

The product obtained had m.p. 199°C. Quinizarin, twice recrystallized from 150 ml of glacial acetic acid, consists of red-orange crystals with m.p. 199°C.

The results of the investigation are given in Table 4.

Table 4

Experiments with the β-methyl ether of alizarin

Two methods for obtaining this ether have been described in the literature. According to Perkin [6], it is obtained by heating a mixture of methyl iodide, benzene, and potassium alizarate in a sealed tube to 230°. According to Grebe and Aders [7], the β-methyl ether is formed already upon shaking a dilute alkaline solution of alizarin with methyl sulfate, or, better, upon heating sodium alizarate with dimethyl sulfate. Attempts to obtain the ether by the indicated methods did not lead to positive results, since by the first method the yield of product does not exceed 7–8%, while by the second it is obtained heavily contaminated with impurities and is difficult to purify. These shortcomings were eliminated by using the following procedure. 3 g of alizarin are mixed with 10 ml of dimethyl sulfate and heated in a flask with a reflux condenser to 120° for 30 min. To the mixture cooled to 40–50°, 20 ml of methyl alcohol are added, and 30 ml of a saturated solution of caustic soda are added in portions through a dropping funnel. To prevent a violently occurring reaction, constant stirring must be used. The resulting brown-violet mass is kept at 120° for another 30 min, then cooled and treated with hydrochloric acid to a neutral reaction. The yellowish precipitate is washed with hot water, dried, and recrystallized from alcohol. The methyl ether of alizarin is a light-brown powder with m.p. 231°.

Results of analysis:

Molecular weight (by Rast):

Experiments with the β-methyl ether of alizarin gave the following results:

Table 5

Thus, with the same time required to reach the maximum e.m.f. (60 min), the β-methyl ether differs noticeably in its magnitude from alizarin itself (340 and 346 mV).

Experiments with xanthopurpurin (1,3-dioxyanthraquinone)

Xanthopurpurin was obtained by reducing purpurin according to the following procedure [8]. Purpurin was added, with stirring, to a strong aqueous solution of ammonia (25-percent \(NH_4OH\)), and then a saturated solution of hydrosulfite was added. After some time, yellow leaflets of xanthopurpurin precipitated; the precipitate was filtered off and washed with hot water. In order to extract the xanthopurpurin more completely, the filtrate was treated with lime, heated to boiling, and, after filtration and acidification with hydrochloric acid, yielded an additional amount of yellow precipitate. On recrystallization from chloroform, xanthopurpurin separated in the form of small bright-yellow crystals with m.p. 259°.

When mordanted fabric was dyed with xanthopurpurin, the following sequence of changes in e.m.f. was observed.

Table 6

Unlike the other oxy derivatives of anthraquinone tested by us, xanthopurpurin gives two e.m.f. maxima: 265 mv after 15 min. and 273 mv after 50 min.

Experiments with purpurin (1,2,4-trioxyanthraquinone)

Purpurin was obtained by oxidizing alizarin according to the method of Rodionov, Bogoslovskii, and Fedorova [9]. A substance with m.p. 269° was subjected to testing.

The results of the experiments with purpurin are presented in Table 7.

Table 7

Table 3

Thus, purpurin gives the greatest electromotive force, the maximum of which is reached 30 min after the mordanted fabric is immersed in the dye solution.

Change in emf in the fixing bath

The appearance of an emf during the interaction of the dye with the aluminum mordant gives grounds to assume that an analogous phenomenon should also occur when the dyed fabric is treated in the fixing bath, i.e., in a solution of a calcium salt. Standard pieces of dyed fabric, moistened with distilled water, were wound onto the mesh electrode and immersed in a solution of calcium acetate (0.001 M). The emf was determined under the same conditions as in all the experiments described above with oxy derivatives of anthraquinone. The results are presented in summary Table 8.

In analyzing the data given in Table 8, attention is drawn first of all to the fact that, of the seven oxy derivatives of anthraquinone tested, five gave a maximum emf after the same interval of time (30 min). With xanthopurpurin and β-oxyanthraquinone this maximum is reached 60 min after the dyed fabric is immersed in the fixing bath, and it is considerably greater than the maximum emf obtained when mordanted fabric is dyed with the same dyes.

α-Oxyanthraquinone and the β-methyl ether of alizarin, both in dyeing and in fixing, gave almost identical maxima of emf, reached in the same time. An analogous picture is observed for quinizarin and alizarin, for which a change in the color of the dyeings during their treatment in the fixing bath is also characteristic.

The similarity in the behavior of different oxy derivatives may apparently be explained by the fact that, in their interaction with metals, there occurs for them

a reaction of one and the same order, the direction of which depends mainly on the position of the hydroxyl groups in the dye molecule. This question will be considered by us in greater detail separately¹.

Conclusions

1. When a fabric treated with aluminum mordant is immersed in a dye solution, an electromotive force arises; its magnitude and the time required to reach the maximum depend on the structure of the oxy derivative of anthraquinone.

2. It was found that $\alpha$-oxyanthraquinone and the $\beta$-methyl ether of alizarin, each having one hydroxyl group in the $\alpha$-position, give almost identical maximum values of the e.m.f. within one and the same interval of time. An analogous phenomenon is observed for dioxy derivatives of anthraquinone (alizarin and quinizarin).

3. Xanthopurpurin and $\beta$-oxyanthraquinone, in which one hydroxyl group is removed from the carbonyl, give the maximum e.m.f. in a shorter time than all the other compounds tested. For xanthopurpurin, with hydroxyl groups in positions 1 and 3, the presence of two e.m.f. maxima is characteristic.

4. The greatest electromotive force is given by the purpurin—oxy derivative of anthraquinone with three hydroxyl groups.

5. When the dyed fabric is treated with a solution of potassium acetate, an identical e.m.f. maximum with the same time required to reach it occurs for $\alpha$-oxyanthraquinone, the methyl ether of alizarin, quinizarin, and purpurin, which indicates that these compounds undergo reactions of one and the same order.

For $\beta$-oxyanthraquinone and xanthopurpurin, under the same conditions, there is a considerable increase in the e.m.f. and in the time required to reach its maximum.

Literature

1. Kulev L. P. and Gorizontova T. N. Zap. Sib. FAN, Trudy khimiko-metallurgicheskogo instituta 4, 3, 1950.
2. Bayer Caro, Ber. 7, 969, Bl., Bd VIII, 338.
3. Il’inskii M. A. Poluprodukty i krasiteli antratsenovogo ryada, GKhTI, Moscow, 198, 1932.
4. Vorozhtsov N. N. Osnovy sinteza poluproduktov i krasitelei, vol. 1, Goskhimizdat, 252, 1940.
5. Il’inskii M. A. Pochetnomu akademiku Il’inskomu, Academy of Sciences of the USSR, Moscow–Leningrad, 317, 1938.
6. Percin, J. Chem. Soc. 434, 1889.
7. C. Graebe, Aders, Lieb. Ann. 318, 360, 1901.
8. Kogan I. M. Khimiya krasitelei (sinteticheskikh), ONTI, Moscow, 599, 1938.
9. Rodionov V. M., Bogoslovskii B. M. and Fedorova A. M. Laboratornoe rukovodstvo po khimii promezhutochnykh produktov i krasitelei, Goskhimizdat, 173, 174, 1948.

1. See the article by L. P. Kulev and T. N. Gorizontova, “On the mechanism of lake formation in alizarin dyeing,” included in this volume. ↩