Research in the Chemistry of Carbazole Derivatives
Abstract Generated abstract
This study examines the oxyethylation, or hydroxyethylation, of carbazole with ethylene oxide under dynamic flow conditions to produce 9-(β-hydroxyethyl)carbazole. Using a glass column packed with granulated potassium hydroxide catalyst, the authors continuously fed a saturated acetone solution of carbazole and ethylene oxide, then evaluated the effects of temperature, ethylene oxide flow rate, carbazole solution flow rate, and catalyst bed height on product yield. The experiments indicate that higher temperatures increase conversion but also promote resin formation, making 50°C the preferred operating temperature. Under optimized conditions, including a 400 mm catalyst layer, an ethylene oxide feed rate of 176 ml/min, and a carbazole solution feed rate of 2.0 ml/min, the target product was obtained in up to 88% of theoretical yield.
Full Text
RESEARCH IN THE CHEMISTRY OF CARBAZOLE DERIVATIVES
XXVII. STUDY OF THE OXYETHYLATION OF CARBAZOLE UNDER DYNAMIC CONDITIONS
E. E. Sirotkina, V. P. Lopatinskii, A. E. Khudyakov
(Presented by the Scientific-Methodological Seminar of the Faculty of Chemical Technology)
In a previous work [1] we established that, in the interaction of carbazole with ethylene oxide under static conditions, 9-(β-oxyethyl)carbazole can be obtained in a yield of more than 90% in the presence of potassium hydroxide in acetone or methyl ethyl ketone medium at 50°C in 50 minutes. It was therefore of interest to test the possibility of attaining high degrees of conversion of carbazole into 9-(β-oxyethyl)carbazole during oxyethylation under dynamic conditions. The oxyethylation apparatus consisted of a glass column equipped with a water jacket and a reflux condenser. Ethylene oxide was fed into the lower part of the column from an evaporator through a bubbler. Its flow rate was measured with a rheometer. Granulated potassium hydroxide was used as the catalyst and the column was packed with it. A saturated solution of carbazole in acetone was continuously fed into the upper part of the column. The passage of ethylene oxide was begun after the solution had been brought to the reaction temperature. The rate of passage of ethylene oxide was regulated by the temperature of the water bath into which the evaporator was immersed. The reaction products were withdrawn from the bottom of the column into water acidified with hydrochloric acid. The precipitate that formed, which was a mixture of carbazole and 9-(β-oxyethyl)carbazole, was filtered off, dried, and weighed, after which carbazole was separated from it. The separation of the unreacted carbazole was based on its poor solubility in carbon tetrachloride, in which 9-(β-oxyethyl)carbazole is readily soluble. Several series of experiments were carried out in this apparatus, in which the dependence of the yields of 9-(β-oxyethyl)carbazole on temperature, on the rates of passage of ethylene oxide and of the acetone solution of carbazole, and also on the height of the catalyst layer was studied. The results of the experiments are summarized in Table 1.
The experiments showed that, as the temperature is increased, the yields of 9-(β-oxyethyl)carbazole increase, and the maximum rate of the process is observed at the boiling point of the solvent. However, the amount of resinification products also increases, so that the optimum temperature is 50°C. It was also established that the yields of 9-(β-oxyethyl)carbazole increase when the rate of passage of the acetone solution of carbazole is decreased to 2.0 ml/min at a catalyst-layer thickness of ...
catalyst of 400 mm and an ethylene oxide feed rate of 176 ml/min. Under the indicated optimal conditions, 9-(β-hydroxyethyl)carbazole can be obtained in a yield of up to 88% of theoretical. Most of the unreacted carbazole can be returned for repeated hydroxyethylation after a single recrystallization.
Table 1
| No. | Reaction temperature, °C | Flow rate of reaction solution, ml/min | Catalyst bed height, mm | Ethylene oxide feed rate, ml/min | Yield of 9-β-hydroxyethylcarbazole, based on reacted carbazole, % of theor. | Yield of 9-β-hydroxyethylcarbazole, based on initial carbazole, % of theor. |
|---|---|---|---|---|---|---|
| 1 | 40 | 3,3 | 400 | 176 | 84,9 | 36,6 |
| 2 | 45 | 3,3 | 400 | 176 | 94,9 | 49,1 |
| 3 | 50 | 3,3 | 400 | 176 | 82,7 | 73,8 |
| 4 | 50 | 4 | 400 | 66 | 70,8 | 21,7 |
| 5 | 50 | 4 | 400 | 107 | 63,8 | 30,8 |
| 6 | 50 | 4 | 400 | 146 | 82,8 | 59,8 |
| 7 | 50 | 4 | 400 | 176 | 94,3 | 64,4 |
| 8 | 50 | 4 | 400 | 226 | 93,2 | 76,9 |
| 9 | 50 | 4 | 300 | 176 | 85,6 | 54,2 |
| 10 | 50 | 4 | 350 | 176 | 93,0 | 62,8 |
| 11 | 50 | 4 | 450 | 176 | 95,9 | 68,8 |
| 12 | 50 | 6,7 | 400 | 176 | 84,0 | 47,5 |
| 13 | 50 | 4 | 400 | 176 | 96,1 | 61,5 |
| 14 | 50 | 3,3 | 400 | 176 | 93,1 | 72,0 |
| 15 | 50 | 2,5 | 400 | 176 | 94,5 | 85,8 |
| 16 | 50 | 2 | 400 | 176 | 90,5 | 88,0 |
Conclusions
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The influence of the principal factors on the process of hydroxyethylation of carbazole under dynamic conditions has been investigated.
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It has been established that, under optimal conditions, 9-(β-hydroxyethyl)carbazole can be obtained in a yield of 88% of theoretical.
Literature
- V. P. Lopatinskii, E. E. Sirotkina, I. P. Zherebtsov. Izv. TPI, 112, 42, 1963.