Study in the Field of the Chemistry of Carbazole Derivatives
Abstract Generated abstract
This study examines thin-layer chromatographic behavior of amino and acylamino derivatives of carbazole on neutral aluminum oxide. Two groups of compounds, 9-alkyl-3-[1-(amino)alkyl]carbazoles and 9-ethyl-3-[1-(acylamino)ethyl]carbazoles, were compared using chloroform, methanol and chloroform, dioxane mobile phases, with detection by ultraviolet light and iodine vapor. The amino derivatives showed greater sorbability and optimal Rf values in chloroform, methanol 97:3, whereas acylamino derivatives generally migrated further in chloroform, dioxane 95:5, with formylamino and meta-aminobenzoylamino compounds as more strongly sorbed exceptions. The results identify solvent systems suitable for distinguishing and separating the two classes of carbazole derivatives.
Full Text
Research in the Chemistry of Carbazole Derivatives
99. Thin-Layer Chromatography of Some Amino Derivatives of Carbazole
L. F. Kovaleva, E. E. Sirotkina, V. P. Lopatinskii
(Submitted by the Scientific-Methodological Seminar
of the Organic Departments and Laboratories of the KhTF)
Conducting research in the chemistry of amino derivatives of carbazole, we studied the behavior of various substituted compounds of this series during chromatography on a thin layer of aluminum oxide.
For the separation of mixtures of substances by a chromatographic method, an important task is the choice of the composition of the mobile phase. A number of researchers have proposed several methods for choosing the composition of the mobile phase [1, 2]. In selecting the chromatographic conditions, we took into account the presence in the molecule of the groups \(NH\) and \(CO\). All the derivatives analyzed were divided into two groups: 9-alkyl-3-[1-(amino)alkyl]carbazoles (compounds I–V, first group); 9-ethyl-3-[1-(acylamino)ethyl]carbazoles (compounds VI–XXI, second group) (Tables 1 and 2, respectively).
It was observed that compounds of the first group have greater sorbability than compounds of the second group. Therefore, they practically remain at the start when \(Al_2O_3\) of activity grade II and the comparatively low-polarity solvent system chloroform–dioxane (95:5) are used. In the solvent system chloroform–methanol (97:3), the \(R_f\) values of these compounds fall within the optimal range (0.39–0.46), while changing the chloroform–methanol ratio to (97:5) increases the \(R_f\) value to 0.7; in this case the spots become less compact. The nature of the substituent \(R_1\) and \(R_2\) under these conditions has almost no effect on the magni-
…on \(R_f\).
The sorbability of the compounds of the second group is, therefore, lower; consequently, when the chloroform–dioxane solvent system (95:5) is used, their \(R_f\) values lie within the range 0.5–0.8.
Table 1
Values of \(R_f\) for 9-alkyl-3-[1-(amino)alkyl]carbazoles
\[ \text{carbazole–}CH(NH_2)R_2,\qquad N\text{-}R_1 \]
| Compound | \(R_1\) | \(R_2\) | Mobile-phase composition: chloroform–methanol (97:3) | Mobile-phase composition: chloroform–methanol (95:5) |
|---|---|---|---|---|
| I | \(C_2H_5\) | \(CH_3\) | 0.39 | 0.70 |
| II | \(C_3H_7\) | \(CH_3\) | 0.42 | 0.70 |
| III | iso-\(C_5H_{11}\) | \(CH_3\) | 0.45 | 0.72 |
| IV | \(C_2H_5\) | \(C_3H_7\) | 0.40 | 0.71 |
| V | \(C_2H_5\) | \(C_6H_5\) | 0.46 | 0.71 |
The exceptions are two compounds of this group—VI and XXI—which are sorbed most strongly; this can be explained by the lesser shielding of the carbonyl group in the case of the formylamino derivative (compound VI) and by the appearance of a new free amino group in the case of the meta-aminobenzoylamino derivative (compound XXI). The nature of the substituent \(R_3\) in compounds X–XX under these conditions also has almost no effect on the value of \(R_f\). When the chloroform–methanol (95:5) solvent system is used, the spots of the compounds of the second group move with the solvent front. The mobile-phase compositions chloroform–dioxane (95:5) and chloroform–methanol (97:3) can be used for separating a mixture of compounds of the first and second groups.
Table 2
Values of \(R_f\) for 9-ethyl-3-[1-(acylamino)ethyl]carbazoles
\[ \text{N-ethylcarbazolyl-}\mathrm{CH(CH_3)-NH-C(=O)-R_3} \]
| Compound | \(R_3\) | Mobile-phase composition: chloroform–dioxane (95:5) | Mobile-phase composition: chloroform–methanol (97:3) |
|---|---|---|---|
| VI | H | 0.29 | 0.53 |
| VII | \(\mathrm{CH_3}\) | 0.53 | 0.56 |
| VIII | \(\mathrm{C_2H_5}\) | 0.64 | 0.65 |
| IX | \(\mathrm{C_3H_7}\) | 0.68 | 0.68 |
| X | \(\mathrm{C_6H_5}\) | 0.79 | |
| XI | \(o\text{-}\mathrm{ClC_6H_4}\) | 0.79 | 0.80 |
| XII | \(m\text{-}\mathrm{ClC_6H_4}\) | 0.78 | |
| XIII | \(o\text{-}\mathrm{BrC_6H_4}\) | 0.79 | 0.79 |
| XIV | \(m\text{-}\mathrm{BrC_6H_4}\) | 0.86 | 0.85 |
| XV | \(p\text{-}\mathrm{BrC_6H_4}\) | 0.88 | |
| XVI | \(o\text{-}\mathrm{NO_2C_6H_4}\) | 0.86 | |
| XVII | \(p\text{-}\mathrm{NO_2C_6H_4}\) | 0.85 | |
| XVIII | \(m\text{-}\mathrm{NO_2C_6H_4}\) | 0.76 | 0.80 |
| XIX | \(\mathrm{C_6H_4{-}CH{=}CH}\) | 0.85 | |
| XX | \(3,4,5\text{-}(\mathrm{OCH_3})\mathrm{C_6H_2}\) | 0.85 | |
| XXI | \(m\text{-}\mathrm{NH_2C_6H_4}\) | 0.26 | 0.50 |
Experimental Part
The starting substances had been synthesized by us previously [3].
Neutral aluminum oxide for chromatography, activity grade II, manufactured by the Donetsk Chemical Reagents Plant, was used as the adsorbent.
The work was carried out in an unfixed layer on glass plates measuring \(10 \times 12\) cm; the run length was 10 cm. The layer thickness in all cases was 1 mm. For chromatography, 0.1–0.4% ethanolic solutions of the substances were used, applied in amounts of 0.005–0.02 ml.
Detection of all substances was carried out in ultraviolet light (UB-I ultrachemiscope) and in iodine vapor.
All \(R_f\) values are averages of 5–6 determinations.
References
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A. A. Akhrem, A. I. Kuznetsova. Thin-Layer Chromatography, “Nauka,” Moscow, 1964.
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N. A. Izmailov. Ukr. Khim. Zhurn., 1954, vol. 20, p. 478.
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E. E. Sirotkina, V. P. Lopatinskii, L. F. Kovaleva, O. T. Yakushina. Izv. TPI, vol. 250 (in press).