Determination of the Unsaturation of 9-Vinylcarbazole
Abstract Generated abstract
A potentiometric method is proposed for determining the unsaturation, and hence monomer content, of 9-vinylcarbazole in colored or turbid solutions where existing analytical procedures are unsuitable. The method is based on rapid addition of mercury acetate to the vinyl group in methanol, with the equivalence point detected from acetic acid formation using a pH meter. Tests of additives relevant to polymerization and telomerization media show that telomer, 9-(2-hydroxyethyl)carbazole, and chlorinated or brominated methanes do not significantly affect the determination, while carbazole causes overestimation. Under optimized methanol conditions, the analysis takes 5 to 10 minutes and gives an unsaturation value of 99.3 ± 0.6%.
Full Text
DETERMINATION OF THE UNSATURATION OF 9-VINYLCARBAZOLE
V. I. Berzin, E. E. Sirotkina, N. A. Ryzhova
(Presented by the scientific-methodological seminar of KhTF)
Existing methods for the analysis of 9-vinylcarbazole (9-VK) [1—3] cannot be used for its determination in colored and turbid solutions, which are encountered in studies of the kinetics of polymerization and especially telomerization in the presence of chlorinated and brominated methanes. For the quantitative determination of 9-VK in colored solutions, the present work used the known reaction of olefins with mercury acetate in methanol according to the following scheme [4]:
\[ \mathrm{R{-}CH{=}CH_2 + Hg(CH_3COO)_2 + CH_3OH \longrightarrow} \]
\[ \mathrm{ \begin{array}{c} \mathrm{R{-}CH{-}CH_2} \\ \ \ \vert \ \ \ \ \ \vert \\ \mathrm{O} \ \ \ \ \mathrm{HgOCOCH_3} \\ \vert \\ \mathrm{CH_3} \end{array} \ + CH_3COOH } \]
As our studies showed, mercury acetate in methanolic solution adds readily and rapidly to 9-VK. The equivalence point was determined from the end of the liberation of acetic acid, which was recorded on an OP-204 universal pH meter.
To develop the optimal conditions for the addition of mercury acetate, 9-VK with \(T_{\mathrm{mp}} = 63—64^\circ\mathrm{C}\) and an unsaturation of \(99.3 \pm 0.5\%\) by the hydrolytic oximercuration method [2] was used. The effect on the course of the analysis of additions of various substances, halogen-containing hydrocarbons, and the solvent used was studied. The experimental data presented in Table 1 show that introduction into the analyzed sample of the 9-vinylcarbazole telomer, 9-(2-oxyethyl)carbazole, and brominated and chlorinated methanes does not change the course of the analysis. The results of the experiments are well reproduced. Addition of carbazole to the reaction mixture causes the analysis results to be overestimated. This fact may be explained by interaction of mercury acetate not only with the monomer, but also with the double bonds of the carbazole nucleus.
An idea of the influence of the solvent on the accuracy of the analysis of 9-VK is given by Fig. 1, from which it is evident that, in methanol, the equivalence point of titration is determined more clearly than in ethanol and isopropanol. This dependence may be explained by differences in the acid-base properties of the alcohols. Subsequently, for determining the unsaturation of monomeric 9-VK, methanol preliminarily distilled over caustic potash was used.
Table 1
Effect of various additives on the results of determining 9-vinylcarbazole
(9-VC sample weight—0.1 g)
| Additive: name | Additive: amount, g | Monomer determined, g | Monomer determined, % of theoretical |
|---|---|---|---|
| — | — | 0.0991 | 99.1 |
| Carbazole | 0.1 | 0.1747 | 174.7 |
| 9-VC telomer | 0.1 | 0.0994 | 99.4 |
| 9-(2-hydroxyethyl)carbazole | 0.1 | 0.0995 | 99.5 |
| CBr₄ | 0.6 | 0.0993 | 99.3 |
| CHBr₃ | 2.9 | 0.0992 | 99.2 |
| CCl₄ | 1.6 | 0.0992 | 99.2 |
| CHCl₃ | 1.5 | 0.0991 | 99.1 |
Fig. 1. Determination of the unsaturation of 9-vinylcarbazole in various solvents. Solvent: 1—methanol, 2—ethanol, 3—isopropyl alcohol.
Procedure for the determination
A 0.1 g sample of 9-VC is placed in a 50 ml beaker, previously washed with chromic mixture and dried; it is dissolved in 2–4 ml of benzene, and 15–20 ml of methanol are added. The beaker is placed on a magnetic stirrer and, with thorough stirring, the reaction mixture is titrated with a 0.15 M solution of mercury acetate in methanol saturated with NaNO₃. The titer of the mercury acetate solution was determined by the method of [5].
The titration is carried out on a universal pH meter of the OP-204 type with an OR-700-1 glass electrode and an OR-810 reference electrode. The titration results are presented graphically, plotting on the ordinate axis the pH of the solution under study and on the abscissa axis the number of milliliters of titrant. The equivalence point is found at the inflection point of the curve. The duration of the analysis is 5–10 minutes.
Calculation of the Analytical Results
The monomer content in the sample is calculated by the formula
\[ A=\frac{T \cdot V \cdot M}{M_1 \cdot g}\cdot 100, \]
where
$A$ — monomer content, %;
$T$ — titer of the mercury acetate solution, g/ml;
$V$ — volume of mercury acetate solution used for titration of the sample, ml;
$M$ — molecular weight of the monomer;
$M_1$ — molecular weight of mercury acetate;
$g$ — weighed portion of monomer, g.
The unsaturation of 9-VC, as determined by this method, is $99.3 \pm 0.6\%$.
REFERENCES
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