Research in the Chemistry of Carbazole Derivatives
Abstract Generated abstract
This study addresses the analytical determination of 9-vinylcarbazole in the presence of carbazole, a mixture for which the mercuric acetate addition method gives unreliable results because carbazole also reacts under the assay conditions. The authors develop a hydrolytic oximation procedure in methanol using hydrochloric acid and hydroxylamine hydrochloride, followed by titration of liberated acid, and examine the effects of acid concentration, hydroxylamine concentration, temperature, and reaction time. The optimized method gives results consistent with catalytic hydrogenation for 9-vinylcarbazole and is applicable to mixtures with carbazole and to 3-chloro-9-vinylcarbazole. The work also indicates increasing resistance to acid hydrolysis in the sequence 9-vinylcarbazole, 3-chloro-9-vinylcarbazole, 3,6-dichloro-9-vinylcarbazole, attributed to decreased nitrogen basicity from chloro substitution.
Full Text
RESEARCH IN THE CHEMISTRY OF CARBAZOLE DERIVATIVES
33. Analysis of 9-Vinyl Derivatives of Carbazole
I. P. ZHEREBTSOV, V. P. LOPATINSKII, L. P. POLTORAKOVA
(Recommended by the scientific-methodological seminar of the Faculty of Chemical Technology)
A rapid and sufficiently accurate method for the analysis of 9-vinylcarbazole and other 9-vinyl derivatives of carbazole is of considerable practical interest. It is known from the literature that, for the analysis of 9-vinylcarbazole, the method of addition of mercuric acetate in methanol at the double bond of the vinyl group can be used successfully [1]. However, it remained unclear how impurities affect the result of the analysis, since preliminary experiments showed that analysis of mixtures of 9-vinylcarbazole with carbazole by this method gives unsatisfactory results.
In the present study it was decided to determine the effect of carbazole on the result of analysis by Martin’s method and to develop a new method of analysis of 9-vinylcarbazole that would make it possible to determine the latter in a mixture with carbazole. It was also of interest to extend this method to other 9-vinyl derivatives of carbazole.
The results of analysis by Martin’s method of mixtures of carbazole with 9-vinylcarbazole containing 80% pure substance (determined by catalytic hydrogenation) are given in Table 1. The data of Table 1 show
Table 1
Results of analysis of mixtures of 80% 9-vinylcarbazole with carbazole by Martin’s method
| No. | Composition of the analyzed mixture: 9-vinylcarbazole, % | Composition of the analyzed mixture: carbazole, % | 9-Vinylcarbazole found, % |
|---|---|---|---|
| 1 | 100 | 0 | 105 |
| 2 | 80 | 20 | 105 |
| 3 | 60 | 40 | 105 |
| 40 | 60 | 102 | |
| 20 | 80 | 101 | |
| 0 | 100 | 101.2 |
the unsuitability of this method for the analysis of mixtures, because mercuric acetate also reacts with carbazole.
Table 2
Study of the influence of various factors on the results of the analysis of 9-vinylcarbazole (80%)
| No. | Temperature, °C | Duration, min | Amount of HCl, ml | Normality of HCl | Normality of hydroxylamine | Analysis result, % |
|---|---|---|---|---|---|---|
| 1 | 45–50 | 30 | 2 | 0.05 | 0.5 | 73.8 |
| 2 | 45–50 | 30 | 2 | 0.05 | 0.5 | 72.9 |
| 3 | 45–50 | 60 | 2 | 0.05 | 0.5 | 74.8 |
| 4 | 45–50 | 60 | 2 | 0.05 | 0.5 | 77.8 |
| 5 | 45–50 | 60 | 2 | 0.05 | 0.5 | 79.3 |
| 6 | 45–50 | 90 | 2 | 0.05 | 0.5 | 79.5 |
| 7 | 45–50 | 120 | 2 | 0.05 | 0.5 | 78.7 |
| 8 | 45–50 | 120 | 2 | 0.05 | 0.5 | 79.1 |
| 9 | 45–50 | 30 | 2 | 0.05 | 1 | 74.2 |
| 10 | 45–50 | 30 | 2 | 0.05 | 1 | 71.8 |
| 11 | 45–50 | 60 | 2 | 0.05 | 1 | 74.3 |
| 12 | 45–50 | 60 | 2 | 0.05 | 1 | 72.7 |
| 13 | 45–50 | 90 | 2 | 0.05 | 1 | 76.0 |
| 14 | 45–50 | 120 | 2 | 0.05 | 1 | 77.5 |
| 15 | 45–50 | 150 | 2 | 0.05 | 1 | 80.0 |
| 16 | 45–50 | 150 | 2 | 0.05 | 1 | 79.0 |
| 17 | boiling | 45 | 1 | 0.1 | 0.5 | 70.3 |
| 18 | boiling | 60 | 1 | 0.1 | 0.5 | 76.5 |
| 19 | boiling | 90 | 1 | 0.1 | 0.5 | 57.7 |
| 20 | 45–50 | 30 | 1 | 0.1 | 0.5 | 61.7 |
| 21 | 45–50 | 60 | 1 | 0.1 | 0.5 | 70.6 |
| 22 | 45–50 | 90 | 1 | 0.1 | 0.5 | 74.0 |
| 23 | 45–50 | 90 | 1 | 0.1 | 0.5 | 80.1 |
| 24 | 45–50 | 120 | 1 | 0.1 | 0.5 | 78.9 |
| 25 | 45–50 | 30 | 1 | 0.2 | 0.5 | 79.5 |
| 26 | 45–50 | 30 | 1 | 0.2 | 0.5 | 80.1 |
| 27 | 45–50 | 45 | 1 | 0.2 | 0.5 | 80.0 |
| 28 | 45–50 | 45 | 1 | 0.2 | 0.5 | 80.0 |
| 29 | 45–50 | 60 | 1 | 0.2 | 0.5 | 80.0 |
| 30 | 45–50 | 30 | 2 | 0.1 | 0.5 | 63.7 |
| 31 | 45–50 | 45 | 2 | 0.1 | 0.5 | 67.6 |
| 32 | 45–50 | 60 | 2 | 0.1 | 0.5 | 71.5 |
| 33 | 45–50 | 90 | 2 | 0.1 | 0.5 | 76.1 |
| 34 | 45–50 | 120 | 2 | 0.1 | 0.5 | 80.6 |
| 35 | 45–50 | 150 | 2 | 0.1 | 0.5 | 80.0 |
For testing as an analytical method for monitoring the purity of 9-vinylcarbazole, we chose the method of hydrolytic oximation proposed for simple vinyl ethers [2]. In doing so, we proceeded from the observations of Clemo and Perkin [3] on the behavior of 9-vinylcarbazole in an acidic medium. They note, in particular, that 9-vinylcarbazole in an alcoholic medium, under the action of hydrochloric acid, rapidly decomposes with almost quantitative liberation of carbazole, if hydrazine hydrate is added to the mixture beforehand. Replacing hydrazine hydrate with hydroxylamine hydrochloride, we hoped to achieve the liberation of hydrochloric acid in an amount equimolecular to 9-vinylcarbazole, which could be titrated. Repetition of Shostakovskii’s procedure with aqueous hydroxylamine did not give a positive result for 9-vinylcarbazole, since under the conditions of the analysis 9-vinylcarbazole melts, and at the interface between the melt and the hydroxylamine solution a dense layer of carbazole forms, preventing the reaction from proceeding to completion. To obtain a homogeneous system, we used methanol as the solvent. When hydrochloric acid is added to a methanolic solution of 9-vinylcarbazole and hydroxylamine hydrochloride, decomposition of 9-vinylcarbazole occurs, carbazole being liberated, while acetaldehyde combines with hydroxylamine.
In the course of the work, the influence of the following factors was studied: the concentration and amount of hydrochloric acid added to the mixture, the concentration of hydroxylamine, and the duration of the reaction.
As is evident from Table 2, the concentration of hydroxylamine has little effect on the results of the analysis, whereas the concentration of water and hydrogen chloride in the mixture has a significant effect; on boiling the mixture, satisfactory results cannot be obtained. By varying these factors it is possible to ob—
Table 3
Influence of various factors on the results of analysis of 3-chloro-9-vinylcarbazole at a temperature of 45–50°C
| No. | Duration, min | Amount of HCl, ml | Normality of HCl | Normality of hydroxylamine | Analysis results, % |
|---|---|---|---|---|---|
| 1 | 30 | 1 | 0.1 | 0.5 | 75.4 |
| 2 | 60 | 1 | 0.1 | 0.5 | 80.1 |
| 3 | 90 | 1 | 0.1 | 0.5 | 92.0 |
| 4 | 120 | 1 | 0.1 | 0.5 | 98.0 |
| 5 | 120 | 1 | 0.1 | 0.5 | 99.5 |
| 6 | 60 | 1 | 0.2 | 0.5 | 99.9 |
| 7 | 120 | 1 | 0.05 | 0.2 | 72.4 |
Table 4
Results of analysis of 98% 3,6-dichloro-9-vinylcarbazole
| No. | Temperature, °C | Duration, min | Amount of HCl, ml | Normality of HCl | Normality of hydroxylamine | Analysis result, % |
|---|---|---|---|---|---|---|
| 1 | 45–50 | 60 | 1 | 0.2 | 0.5 | 0 |
| 2 | boiling | 60 | 1 | 0.2 | 0.5 | 87.7 |
| 3 | 80* | 120 | 1 | 0.2 | 0.5 | 81.5 |
*) aqueous solution of hydroxylamine
slow down or accelerate the rate of hydrolysis, and also to choose the optimal conditions for analysis. The results of analyses of 9-vinylcarbazole obtained by this method agree well with the results obtained in its catalytic hydrogenation. It also turned out that 9-vinylcarbazole substituted in the nucleus undergoes hydrolysis under these conditions, with their stability increasing in the following order: 9-vinylcarbazole, 3-chloro-9-vinylcarbazole, 3,6-dichloro-9-vinylcarbazole. However, 3-chloro-9-vinylcarbazole can be hydrolyzed quantitatively under the conditions used for the analysis of 9-vinylcarbazole. The results of analysis of substituted 9-vinylcarbazoles are given in Tables 3 and 4.
The greater stability of chloro-substituted 9-vinylcarbazoles can be explained by the decrease in the basicity of nitrogen upon introduction of electron-withdrawing substituents (chlorine) into the carbazole molecule.
The facts presented make it possible to suppose that, under conditions of cationic polymerization, the activity of substituted 9-vinylcarbazoles will decrease with decreasing basicity of nitrogen.
Experimental Part
Starting Reagents
Carbazole—a reagent from the Kharkov Coke-Chemical Plant—was purified by recrystallization from acetone to a melting point of 244°C.
9-Vinylcarbazole was prepared according to the known procedure [4]. It contained 80% 9-vinylcarbazole and 20% carbazole, m.p. 63–64°C. 3-Chloro-9-vinylcarbazole, m.p. 69°C. 3,6-Dichloro-9-vinylcarbazole, m.p. 135–136°C.
Hydroxylamine hydrochloride, “pure,” was purified by recrystallization from water.
Methanol, “pure,” was freed from acidic impurities by distillation over caustic potash.
The working procedure consisted in dissolving a weighed portion of 9-vinylcarbazole (0.2 g) in 25 ml of a methanolic solution of hydroxylamine hydrochloride, adding hydrochloric acid, and keeping the mixture in a water bath in a tightly closed flask at a specified temperature for a specified time. The hydrochloric acid liberated upon cooling was titrated with 0.5 N NaOH in the presence of 5 drops of bromophenol blue. At the same time a blank experiment was carried out with the addition (or without it) of approximately 0.2 g of carbazole. The amount of 9-vinylcarbazole was calculated by the formula:
\[ \frac{M \cdot N_{\mathrm{NaOH}}(a_1-a_2)}{g \cdot 10}, \]
where \(M\) is the molecular weight of 9-vinylcarbazole;
\(N_{\mathrm{NaOH}}\) is the normality of NaOH;
\(a_1\) is the number of ml of NaOH used for titration of the sample;
\(a_2\) is the number of ml of NaOH used for titration of the blank sample.
The most accurate and reproducible results were obtained when the sample was heated in 25 ml of a 0.5 N solution of hydroxylamine hydrochloride in the presence of 1 ml of 0.2 N hydrochloric acid for one hour.
Conclusions
- It has been shown that Martin’s method is unsuitable for the analysis of mixtures of 9-vinylcarbazole with carbazole.
-
A method has been proposed and developed for the analysis of 9-vinylcarbazole, based on its hydrolysis in methanol in the presence of hydrochloric acid and hydroxylamine hydrochloride.
-
It has been shown that the method can be applied to the analysis of mixtures of 9-vinylcarbazole with carbazole.
-
It has been found that the developed method can be extended to 3-chloro-9-vinylcarbazole; it has been shown that the resistance of 9-vinylcarbazoles to acid hydrolysis increases in the series: 9-vinylcarbazole < 3-chloro-9-vinylcarbazole < 3,6-dichloro-9-vinylcarbazole.
REFERENCES
- R. Martin. Anal. Chem., 21, 921, 1949.
- M. F. Shostakovskii, E. N. Prilezhaeva. ZhOKh, 17, 1129, 1947.
- G. R. Clemo, W. Perkin. J. Chem. Soc., 125, 1804, 1924.
- V. P. Lopatinskii, E. E. Sirotkina, I. P. Zherebtsov. Izv. TPI, 112, 42, 1963.