Research in the Chemistry of Carbazole Derivatives
Abstract Generated abstract
This study examines the donor strength of carbazole and selected carbazole derivatives through their complex formation with picric acid in 1,2-dichloroethane at 20°C. Spectrophotometric measurements at 508 and 536 nm were used to determine complex composition by the Asmus method and stability constants by the Frank-Oswald graphical method. All investigated complexes were found to have 1:1 composition, while stability constants showed that 9-alkylcarbazoles have complex-forming ability close to carbazole, whereas chlorine substitution in the carbazole nucleus substantially reduces donor strength. The decrease is attributed to the electron-withdrawing effect of chlorine, consistent with the greater acidity reported for chlorinated carbazoles.
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PROCEEDINGS
OF THE TOMSK POLYTECHNIC INSTITUTE NAMED AFTER S. M. KIROV,
ORDER OF THE OCTOBER REVOLUTION AND ORDER OF THE RED BANNER OF LABOR
Vol. 257 1973
RESEARCH IN THE CHEMISTRY OF CARBAZOLE DERIVATIVES
93. Study of the Donor Strength of Carbazole Derivatives during Complex Formation with Picric Acid
I. P. Zherebtsov, N. D. Balandina, V. P. Lopatinskii
(Presented by the Scientific-Methodological Seminar of the Faculty of Chemical Technology)
This communication presents the results of a study of complex formation of carbazole and some of its derivatives with picric acid in 1,2-dichloroethane at 20°C. The measurements were carried out on an FEK-N-57 instrument using the fourth and fifth filters (508 and 536 nm, respectively). In this region of the spectrum, both the donors and acceptors studied by us do not absorb light appreciably, whereas absorption by the complexes is clearly recorded. The composition of the complexes, determined by Asmus’s straight-line method [1], proved in all cases to be 1:1, which made it possible to use the graphical Frank–Oswald method [1] to determine the stability of the complexes. From the results given in the table it follows that 9-alkylcarbazoles have a complex-forming ability approximately equal to that of carbazole, while the introduction of chlorine atoms into the carbazole nucleus substantially lowers it. The latter fact may be explained by the electron-withdrawing action of the substituent, which reduces the mobility of the electron system in the carbazole nucleus. The comparatively low stability constants of chloro-substituted carbazoles are consistent with the increased acidity, compared with carbazole, of carbazoles substituted by chlorine in the nucleus [2].
The value of the stability constant for carbazole agrees well with that found in work [3], especially if one takes into account the difference in the dielectric constants of the solvents used by us and in work [3] (chloroform).
The table gives the values of the stability constants of the complexes (in calculating the constants, the concentrations of the reagents were expressed in moles per liter).
| Donor | Stability constants, 508 nm | Stability constants, 536 nm |
|---|---|---|
| Carbazole | 3,56 | 3,59 |
| 9-Methylcarbazole | 4,08 | 3,88 |
| 9-Ethylcarbazole | 3,51 | 3,68 |
| 9-n-Propylcarbazole | 3,48 | 3,56 |
| 9-n-Butylcarbazole | 3,33 | 3,34 |
| 9-Benzylcarbazole | 4,67 | 4,78 |
| 3-Chloro-9-methylcarbazole | 1,96 | 1,75 |
| 3-Chloro-9-n-butylcarbazole | 1,70 | 1,72 |
| 3-Chloro-9-benzylcarbazole | 1,52 | 1,48 |
| 3,6-Dichlorocarbazole | 0,54 | – |
| 9-(2-Hydroxy)ethylcarbazole | 2,35 | 2,42 |
| 3-Chloro-9-(2-hydroxy)ethylcarbazole | 2,11 | 2,18 |
| Acrylate of 9-(2-hydroxy)ethylcarbazole | 1,33 | 1,66 |
| Methacrylate of 9-(2-hydroxy)ethylcarbazole | 3,98 | 3,92 |
Literature
- Spectroscopic Methods in the Chemistry of Complex Compounds. Collection edited by V. M. Vdovenko, Moscow, 1963.
- I. P. Zherebtsov, V. P. Lopashinskii, Izv. TPI, 163, 12, 1970.
- A. E. Lutskii, I. I. Menshova, L. A. Fedotova, M. G. Voronkov, ZhOKh, 39, 645, 1969.