STUDY IN THE CHEMISTRY OF CARBAZOLE DERIVATIVES

71. TELOMERIZATION OF 9-VINYLCARBAZOLE

V. I. BERZIN, E. E. SIROTKINA, V. P. LOPATINSKII, V. M. SUTYAGIN

(Presented by the scientific-methodological seminar of the Faculty of Chemical Technology)

Poly-9-vinylcarbazole (PVK) has found industrial application for obtaining heat-resistant electrical insulating materials [1], and in recent years for manufacturing, on its basis, photosensitive electrographic layers [2].

From the literature [3—6] it is known that 9-vinylcarbazole (9-VC) polymerizes in carbon tetrachloride solution under irradiation with direct sunlight or ultraviolet light.

The resulting polymers contain chlorine as terminal groups. It seemed interesting and practically important to study the telomerization of 9-VC in the presence of radical-type initiators.

The telomerization of 9-vinylcarbazole was carried out in carbon tetrachloride solution at 75° in the presence of benzoyl peroxide (BP). The degree of conversion of the monomer into telomer was judged from the yield of telomers and from the conversion, which was determined from the amount of free 9-VC in the reaction mass by the method of hydrolytic oxidation [7]. Discrepancies between parallel determinations did not exceed 1%. Isolation of the telomers from the carbon tetrachloride solution was carried out by precipitation into ethyl alcohol, and this fraction was conventionally called the “high-molecular-weight” fraction (HMF), while the products isolated from the mother liquor were called the “low-molecular-weight” fraction (LMF).

The dependence of the telomer yield on the conditions of the process was studied as follows: for the dependence on the duration of the process—in the presence of \(2.4 \cdot 10^{-4}\) mole (3 wt. %) BP and an initial monomer concentration of 0.052 mole/l; for the study of the effect of the amount of initiator—at a monomer concentration of 0.052 mole/l and a reaction time of 120 min; for the study of the effect of the amount of solvent—in the presence of \(2.4 \cdot 10^{-4}\) mole (3 wt. %) BP and a reaction time of 240 min.

It follows from Fig. 1 that the yield of HMF increases with increasing reaction time up to a certain value (70%), whereas the yield of LMF decreases, with the LMF yield curve passing through a maximum. The total conversion of monomer into telomers also increases, reaching more than 90%. We subsequently showed that, depending on the amount of initiator and the initial monomer concentration, the process can be directed toward changing the ratio of HMF and LMF yields.

As can be seen from Fig. 2, the yield of HMF and the total conversion increase with increasing initiator concentration up to a certain value, while the yield of LMF decreases.

Fig. 1. Dependence of telomer yield on reaction duration: 1 — monomer conversion, 2 — VMF yield, 3 — NMF yield.

Fig. 2. Dependence of telomer yield on the amount of initiator: 1 — monomer conversion, 2 — VMF yield, 3 — NMF yield.

It follows from Fig. 3 that the yield of VMF and NMF decreases upon dilution of the monomer. The overall conversion of 9-VK also decreases, which is characteristic of radical-type processes. The measurements of the intrinsic viscosity of VMF that were carried out are presented in Fig. 4. As can be seen from the data obtained, the viscosity of VMF increases with increasing reaction duration and decreases with increasing amount of initiator and with dilution of the monomer.

As for NMF, its viscosity could not be measured, since under analogous conditions it is insoluble in benzene.

Fig. 3. Dependence of the yield of telomers on the initial monomer concentration. 1—monomer conversion, 2—VMF yield, 3—NMF yield.

Fig. 4. Dependence of the characteristic viscosity of VMF on the process conditions: 1—on the reaction time, 2—on the initiator concentration, 3—on the amount of solvent.
\(\tau\)—reaction time (min), \((I)\)—initiator concentration (wt. %), \((S)\)—amount of solvent \(\left(\dfrac{\text{ml}}{2\ \text{g of }9\text{-VK}}\right)\).

Experimental Part

9-VK, prepared by the procedure of [8], had a melting point of 64–65°C with an unsaturated-compound content of 99.8–99.9%, as determined by the method of addition of mercuric acetate [9] and by the method of hydrolytic oxidation [7]. Benzoyl peroxide was recrystallized twice from ethanol before use. Carbon tetrachloride of “chemically pure” grade was used.

Telomerization of 9-VK. Into a three-necked round-bottom flask with a capacity of

250 ml, equipped with a thermometer and stirrer, a weighed portion of the monomer and carbon tetrachloride are charged successively. After the specified temperature is reached, BP is introduced.

After completion of the reaction, the telomer formed is precipitated with an equal volume of ethanol; the precipitate (HMF) is transferred to preweighed filters, washed with hot alcohol until the monomer and carbon tetrachloride are completely removed (the completeness of washing from carbon tetrachloride was monitored by resorcinol [10]), dried to constant weight, and the yield is determined. The excess ethanol and carbon tetrachloride are distilled off from the mother liquor, the residue is dissolved in 15 ml of acetone and precipitated in 100 ml of distilled water. The precipitated product (LMF) is transferred to preweighed filters, washed with distilled water, dried, and the yield is determined.

HMF is a light-brown powder with a softening temperature of 180–190°, readily soluble in benzene.

LMF is a yellow crystalline product with a softening temperature of 160–180°, readily soluble in acetone. No special studies of LMF were carried out.

Conclusions

1. The telomerization of 9-vinylcarbazole in a solution of carbon tetrachloride at 75° in the presence of benzoyl peroxide was studied.

2. It was shown that, depending on the reaction conditions, products with different molecular weights are formed during the telomerization of 9-vinylcarbazole.

3. The dependence of the yield and characteristic viscosity of the telomers on the reaction duration, the amount of initiator, and the initial concentration of the monomer was studied.

REFERENCES

1. H. R. Jacobi, Kunststoffe, 43, 381 (1953).

2. I. B. Sidaravichyus. Problems of Radio Electronics, Series XII, issue 25, 105 (1964).

3. A. Schapiro, G. Hardy, J. Chem. Phys., 59, 993 (1962).

4. J. Breitenbach, J. W. Srna, J. Polymer Sci., 1, 263 (1963).

5. H. Scott, H. Labes, J. Polymer Sci., 1, 413 (1963).

6. M. Biswas, S. Chosal, Chem. and Ind., 41, 1717 (1966).

7. I. P. Zherebtsov, Candidate’s dissertation. Tomsk, 1967.

8. V. P. Lopatinskii, Yu. P. Shekhirev, V. M. Sutyagin, A. P. Bychkova. Methods for Obtaining Chemical Reagents and Preparations. IREA, Moscow, (in press).

9. R. W. Martin, Analyt. Chem., 21, 921 (1949).

10. M. D. Shvaikova. Forensic Chemistry. Meditsina Publishing House, Moscow, 1965.