Research in the Chemistry of Carbazole Derivatives. Ionization Constants of Some Amino Derivatives of 9-Substituted Carbazoles
Abstract Generated abstract
A series of amino derivatives of 9-substituted carbazoles was synthesized and examined to determine how substituent structure affects basicity. Apparent ionization constants were measured by potentiometric titration at the half-neutralization point in 20 percent ethanol at 25 degrees Celsius, using hydrochloric acid and repeated pH determinations. The reported constants show that increasing steric bulk near the carbazole nitrogen or aminoalkyl side chain weakens basic properties, while an electron-accepting chloro substituent in the 6-position also lowers basicity. The authors interpret these trends through steric hindrance in ammonium ion formation and, for aromatic substituents near the basic center, electronic delocalization that reduces proton-binding availability.
Full Text
of two-phase bentonite suspensions, with increasing bentonite concentration, into a single pseudophase has been experimentally confirmed by special studies carried out at the Department of General Chemical Technology of TPI.
The high sensitivity of the rheological properties of pore suspensions to the influence of various surface-active additives, which change the degree of colloidality and hydrophilicity of the raw-material mixture, makes it possible easily to regulate the plasticity of the systems being fired and thereby the thermal stability of the capillary-porous bodies formed.
In addition, the results obtained can be used in the technology of granulation of disperse materials as a basis for reducing the amount of plasticizing additives in the raw mixtures being fired. Thus, in particular, the use of the temperature effect of plasticization during pelletizing of iron-ore concentrates makes it possible to substantially reduce bentonite consumption.
Literature
- M. V. Volarovich, “Colloid Chemistry,” No. 6, 1966.
STUDY IN THE CHEMISTRY OF CARBAZOLE DERIVATIVES.
IONIZATION CONSTANTS OF SOME AMINO DERIVATIVES
OF 9-SUBSTITUTED CARBAZOLE
E. E. Sirotkina, V. P. Lopatinskii, L. F. Kovaleva, T. V. Kakalina
A series of amino derivatives of 9-alkylcarbazoles was synthesized in this work by the procedure described in /1/, and their apparent ionization constant was measured by the method of potentiometric titration at the pH of half-neutralization of the solutions in 20% ethyl alcohol /2/.
The ionization constants obtained for the amines agree well with the steric and electronic influence of the substituents.
The basicity constants of 9-alkyl-3-(I-aminoethyl)carbazole and 9-ethyl-6-chloro-3-(I-aminoethyl)carbazole, given in the table, show that electron-acceptor substituents in the 6-position of carbazole decrease the basicity of the amines.
Table 1
Ionization constants of
9-alkyl-3-(1-aminoalkyl)carbazoles
| No. | \(R_1\) | \(R_2\) | \(X\) | \(\mathrm{p}K_B\) |
|---|---|---|---|---|
| 1 | \(\mathrm{CH_3}\) | \(\mathrm{CH_3}\) | \(\mathrm{H}\) | 4.85 |
| 2 | \(\mathrm{C_2H_5}\) | \(\mathrm{CH_3}\) | \(\mathrm{H}\) | 4.95 |
| 3 | \(\mathrm{C_3H_7}\) | \(\mathrm{CH_3}\) | \(\mathrm{H}\) | 5.35 |
| 4 | \(\mathrm{C_3H_7}\)-iso | \(\mathrm{CH_3}\) | \(\mathrm{H}\) | 5.4 |
| 5 | \(\mathrm{C_4H_9}\) | \(\mathrm{CH_3}\) | \(\mathrm{H}\) | 5.65 |
| 6 | \(\mathrm{C_5H_{11}}\)-n | \(\mathrm{CH_3}\) | \(\mathrm{H}\) | 5.9 |
| 7 | \(\mathrm{C_5H_{11}}\)-iso | \(\mathrm{CH_3}\) | \(\mathrm{H}\) | 6.1 |
| 8 | \(\mathrm{CH_2C_6H_5}\) | \(\mathrm{CH_3}\) | \(\mathrm{H}\) | 6.23 |
| 9 | \(\mathrm{C_2H_5}\) | \(\mathrm{CH_3}\) | \(\mathrm{Cl}\) | 6.05 |
| 10 | \(\mathrm{C_2H_5}\) | \(\mathrm{C_2H_5}\) | \(\mathrm{H}\) | 5.73 |
| 11 | \(\mathrm{C_2H_5}\) | \(\mathrm{C_3H_7}\) | \(\mathrm{H}\) | 6.13 |
| 12 | \(\mathrm{C_2H_5}\) | \(\mathrm{C_6H_5}\) | \(\mathrm{H}\) | 7.55 |
With an increase in the bulk of the substituent in the 9-position of carbazole, the basicity of the amine decreases. This can apparently be explained by the fact that, upon transition to the cation, strain arises as a result of the forced convergence of spatially adjacent groups, and formation of the ammonium ion proves energetically unfavorable. Therefore, in the series of amines from 1 to 8, a weakening of the basic properties is observed. The lower, and markedly lower, basicity of amines 10, 11, and 12 compared with amine 2 can also be explained by steric hindrance during the transition of the amine to the cation and by an electronic factor in the case of amine 12, since substituents of aromatic character near the basic center strongly weaken the basic properties. This is due to the conjugation effect of the \(p\)-\(\pi\) unshared electrons
nitrogen electrons with the $\pi$-electrons of the nucleus; as a result of such an electronic displacement (of the $E_g$ type), the nitrogen atom does not have its unshared electrons fully available for binding the proton.
Experimental Part
The determination of pK values for 9-alkyl-3-(1-aminoalkyl)carbazoles was carried out in a mixture of 80% water and 20% ethanol, by the pH of half-neutralized $1 \cdot 10^{-2}$ molar solutions of the amines. The titration was conducted at a temperature of $(25 \pm 1)^\circ\mathrm{C}$ with a $0.1\,N$ solution of hydrochloric acid.
The pH was measured with a universal pH meter of the OP-204 type, with a glass electrode of the OP 700-[[unclear: digit]] type and a calomel reference electrode of the OP 801 type. The correctness of the pH-meter readings and the linearity of its scale were checked using 3 buffer solutions in accordance with the instrument certificate.
For each of the amines, the mean pH value was taken from 3–4 determinations. The deviation of the results of individual measurements did not exceed $\pm 0.03$ pH units. For diethylamine the pK value is 3.38; according to the data of work /3/ — pK 3.0277.
Literature
- E. E. Sirotkina, V. P. Lopatinskii, L. F. Kovaleva, O. G. Yakushina. Izv. TPI, vol. 250 (in press).
- A. Albert, E. Serjeant. The Ionization Constants of Acids and Bases. Moscow–Leningrad, “Khimiya,” 1964.
- K. D. Neničescu. Organic Chemistry, vol. I. Moscow, Izdatinlit, 1963.
THEORY OF THE MUTUAL INFLUENCE OF ELEMENTS IN THE METHOD OF STRIPPING FILM POLAROGRAPHY. A PARAMETRIC APPROACH
A. A. Kashin, T. F. Ryashentseva, A. G. Stromberg
In a number of works on stripping film polarography (SFP), the mutual influence of two metals on a solid electrode has been experimentally detected /1–3/. A quantitative interpretation of the effect of the mutual influence of elements on a solid electrode has so far