is not accompanied by fundamental changes in the kinetic regularities of the processes of mass and heat transfer and chemical reaction. In this connection, the design of industrial equipment can be carried out on the basis of laboratory studies by the method of scale modeling.

Literature

1. N. P. Kurin, N. F. Stas’. ZhPKh, 44, 1710, 1971.
2. N. P. Kurin, N. F. Stas’. ZhPKh, 44, 2251, 1971.

Research in the Chemistry of Carbazole Derivatives. Study of the Mechanism of the Interaction of Olefin Oxides with Carbazoles in an Alkaline Medium. II. Kinetics of the Interaction of Propylene Oxide with Nitrocarbazoles.

I. P. Zherebtsov, V. P. Lopatinskii, S. P. Yudina, V. V. Gal’tsova, T. N. Zorina

Previously /1/ the kinetics of the reaction of 3-nitrocarbazole (3-NC) with propylene oxide under conditions of base catalysis was studied. It was shown that the reaction consists of several stages, the first of which is the ionization of 3-NC under the action of potassium hydroxide and the medium. In the second, rate-limiting, stage, a trimolecular complex is formed, consisting of 3-NC, propylene oxide, and a proton-donor solvent (alcohol).

It was of interest to follow the behavior, in this reaction at both stages, of nitrocarbazoles having both electron-acceptor and electron-donor substituents in the nucleus. We studied the kinetics of the reaction in ethyl alcohol for the following nitrocarbazoles: 3-methyl-6-nitrocarbazole (3-Me-6-NC), 3-chloro-6-nitrocarbazole (3-Cl-6-NC), 3-iodo-6-nitrocarbazole (3-I-6-NC), and 3,6-dinitrocarbazole (3,6-DNC).

All these compounds are weak acids capable, upon ionization, of giving, like 3-NC, colored anions, whose optical properties make it possible to use the photometric method to monitor unreacted nitrocarbazole /2/.

The pKa values of the nitrocarbazoles as acids are given in the table.

Table 1

Kinetic and thermodynamic characteristics of the process
$T^\circ = 50^\circ\mathrm{C}$

As can be seen from the table, the higher the acidity of nitrocarbazole, the greater the concentration of the active particle—its anion—entering into reaction with propylene oxide in the limiting stage, all other conditions being equal.

As for 3-NC /1/, the effective constant ($K_{\mathrm{eff}}$) for all its substituted derivatives increases with increasing acidity function $H^-$. In logarithmic coordinates this dependence has the form of a straight line with different slopes for each substituted nitrocarbazole. Plotting the logarithms of the tangents of these angles on the ordinate axis and the $\sigma^-$ Hammett constants on the abscissa axis, one can obtain a straight line with slope $\rho = +0.76$, which in our case reflects the influence of the substituents on the overall rate of the process (correlation coefficient of the straight line 0.99).

The absolute value obtained for $\rho$ indicates that the introduction of substituents into the nucleus of 3-NC substantially changes its behavior in the reaction under study. Moreover, electron-acceptor substituents promote an increase in the effective rate, probably as a consequence of an increase in the degree of ionization, as indicated by the positive sign of $\rho$.

Since the nucleophilic ability of an acid anion usually decreases with increasing acidity, it may be assumed that the rate of the limiting stage of the interaction of nitrocarbazoles with propylene oxide should decrease as the acidity of the substituted nitrocarbazole increases.

Investigation of the limiting stage is the subject of our further work.

Experimental Part

3-NC was obtained according to /3/, m.p. 214°.

3-I-6-NC was obtained by nitration of 3-iodocarbazole, m.p. 250°.

3-Cl-6-NC was obtained by nitration of 3-chlorocarbazole, m.p. 282–283°; literature data /4/: m.p. 284°.

3-M-6-NC was obtained by nitration of 3-methylcarbazole, m.p. 192°.

3,6-DNC was obtained according to /5/, m.p. 383–384°.

The reaction of nitrocarbazoles with propylene oxide was studied at initial concentrations of nitrocarbazoles (2.34–4.06 M), potassium ethoxide (0.0004–0.048 M), and an excess of propylene oxide (10 moles). Ethyl alcohol was purified according to a known procedure /6/. To measure the apparent rate constants of the reactions, a photometric method was used for measuring the concentration of nitrocarbazole that had not entered into the reaction, as described in /2/.

Literature

1. I. P. Zherebtsov, V. P. Lopatinskii, S. P. Yudina, Z. A. Michurina. Izvestiya TPI, vol. 257, 1973.
2. V. P. Lopatinskii, I. P. Zherebtsov, S. P. Yudina, L. P. Belyanina. Izvestiya TPI, same collection.
3. R. K. Eikhman, V. O. Lukashevich, E. A. Silaeva. POKh, 6, 93, 1939.
4. Y. Y. Coker, S. Y. Plant, P. B. Turner. J. Chem. Soc., 110, 1951.
5. H. M. Grotta, C. J. Riggle, A. B. Bearse. J. Org. Chem., 29, No. 8, 2474, 1964.
6. A. Weissberger et al. Organic Solvents. Izd. IL, Moscow, 1958.

STUDIES ON THE DETERMINATION OF MOLYBDENUM BY THE METHOD OF POLAROGRAPHY WITH ACCUMULATION

A. A. Kashin, V. F. Slipchenko, N. N. Zubkova

It is known that the method of inverse chronopotentiometry makes it possible to determine \(10^{-3}\)–\(5 \cdot 10^{-6}\) M molybdenum on a mercury electrode [1–3]. It has been shown that the introduction of certain amounts of \(H_2O_2\) (30%) increases the sensitivity of molybdenum determination [3]. Anodic peaks of Mo(VI) have been obtained on a graphite electrode by the method of inverse voltammetry [4]; however, in that work a very complex background was chosen for the determination of molybdenum.

We studied the possibility of determining microquantities of molybdenum by the PA method on backgrounds of simpler composition, also using a graphite electrode.

The experiment was carried out on an OH-102 polarograph; the rate of potential change was 500 mV/min. An electrolyzer with insert cups was used in the work. Standard molybdenum solutions were prepared from the reagent \((NH_4)_2MoO_4\).

Clearly defined anodic peaks of Mo(VI) were obtained against a background of