RESEARCH IN THE CHEMISTRY OF CARBAZOLE DERIVATIVES

III. Vinylation of Carbazole with Vinyl Acetate and the Synthesis of Poly(9-vinylcarbazole)

V. P. Lopatinskii, E. E. Sirotkina

(Presented by Professor, Doctor of Chemical Sciences T. P. Kutova)

At present, one technical method is known for obtaining 9-vinylcarbazole, consisting in the action of acetylene on carbazole under pressure, at high temperature and in the presence of basic catalysts [1]. Other methods for the synthesis of 9-vinylcarbazole lead to low yields of the monomer [1, 3, 4]. 9-Vinylcarbazole possesses appreciable toxicity [1, 2]. The polymer of 9-vinylcarbazole is obtained by polymerization of the monomer by known methods and has practical application in electrical engineering [1, 2, 3, 5].

The proposed method for obtaining the polymer of 9-vinylcarbazole differs from all previously proposed methods in that polyvinylcarbazole is formed directly from carbazole upon its interaction with complex vinyl ethers, for example vinyl acetate. The 9-vinylcarbazole formed as an intermediate product polymerizes under the reaction conditions, as a result of which the final product of the interaction of carbazole and the vinyl ether is poly-9-vinylcarbazole.

Thus, the process of obtaining polyvinylcarbazole is shortened by one stage and is also very convenient because of the toxicity of the monomer. The reaction is carried out with equimolecular amounts of carbazole and vinyl ether in a solution of aliphatic ketones, in the temperature range from −50°C to +50°C and in the presence of catalysts containing divalent mercury. Addition of sulfuric acid accelerates polymerization. Quantitative conversion of carbazole into poly-9-vinylcarbazole is achieved, depending on the temperature, in 2–24 hours. The polymer may be isolated from the solution by adding water or alcohols. It has the appearance of dense flakes of light cream color, which are easily ground into powder after drying; it is infinitely soluble in aromatic hydrocarbons, swells and partially dissolves in ketones, is sparingly soluble in aliphatic alcohols, and is insoluble in water. The composition and structure of the polymer as poly-9-vinylcarbazole are confirmed by the results of analyses for nitrogen content, a positive reaction with monochloroacetic acid [6], and quantitative

with the formation of acids liberated during decomposition of complex vinyl ethers and the absence of acetaldehyde in the reaction products. The polymer does not give a nitroso derivative. Under the conditions described, formation of poly-9-vinylcarbazole from 9-substituted carbazoles does not occur.

The proposed method leads to the quantitative conversion of carbazole into poly-9-vinylcarbazole. Under other conditions the reaction of carbazole with vinyl ethers has been studied previously [8, 9], but leads to different results.

Experimental Part

Polymer of 9-vinylcarbazole. Into a three-necked flask equipped with a thermometer, stirrer, dropping funnel and, if necessary, a reflux condenser, and placed in a thermostat, are charged 100 ml of acetone and 0.64 g of mercury acetate \([(CH_3COO)_2Hg]\), prepared from mercuric oxide by the known method [7]. With stirring, 0.092 ml of sulfuric acid (sp. gr. 1.84) is added, and then 50 g of “pure” grade carbazole is introduced (reagent of the Kharkov Coke-Chemical Plant). 27.5 ml of freshly distilled vinyl acetate is added dropwise over 1.5 hours with continuous stirring. The reaction is carried out at a constant temperature of 20 ± 2°C for 24 hours. After completion of the reaction, 100–150 ml of benzene is added to the contents of the flask to dissolve the polymer, part of which may be present as a precipitate. The solution is filtered from the catalyst, and the polymer is isolated either by precipitation with water or by pouring the solution into 600 ml of methyl alcohol with stirring. Precipitation with water gives a quantitative yield of polymer. The yield of the high-molecular-weight polymer fraction (molecular weight 5000 by viscosity), precipitated with methyl alcohol from the benzene–acetone solution, reaches 80–85% of the theoretical. The softening temperature of the polymer is about 200°C (in a capillary).

Found, %: N 6.90; 6.94; 7.46; 6.89.
Calculated, %: N 7.25 (for \((C_{14}H_{11}N)_n\)).

Acetic acid content: found 18.07 g; 18.10 g; calculated 18.12 g.

Conclusions

1. A method has been developed for obtaining the polymer of 9-vinylcarbazole.
2. The method gives good yields of poly-9-vinylcarbazole and has an advantage over known methods, since it eliminates the need to obtain a toxic monomer.

Literature

1. Monomers, collection 2, Izdatinlit, 93, 1953.
2. Vinyl Acetylene, Izdatinlit, 207, 1954.
3. H. R. Jacobs, Kunststoffe, 43, 381, 1953.
4. O. Solomon, C. Ionescu, I. Ciuta, Chem. Technik, 9, 202, 1957.
5. E. I. Barg, Technology of Synthetic Plastic Materials, Goskhimizdat, 227, 1954.
6. H. Winterscheidt, C. A. 48, 12456, 1954.
7. Yu. V. Karyakin, I. I. Angelov, Pure Chemical Reagents, Goskhimizdat, 463, 1955.
8. J. Furukawa, M. Goi, C. A. 48, 6427, 1954.
9. S. N. Ushakov, A. F. Nikolaev, Izv. AN SSSR, OKhN, 1, 83, 1955; 2, 226, 1956.