PHYSICOCHEMICAL ANALYSIS OF SYSTEMS CONTAINING PHENOLS

A. S. NAUMOVA, V. S. SMORODINOV

(Presented by Prof. B. V. Tronov, Doctor of Chemical Sciences)

The present work, like the study carried out earlier, was undertaken in order to determine how often complex molecular compounds containing three or more molecules of one of the components occur in the liquid phase.

By the methods of physicochemical analysis we studied the systems: aniline–phenol, quinoline–p-nitrophenol, quinoline–m-nitrophenol, α-naphthylamine–α-naphthol.

Experimental Part

The following were taken for the work: phenol (m.p. 41.3°), aniline (m.p. −6.2°), quinoline (m.p. −15°), m-nitrophenol (m.p. 96°), p-nitrophenol (m.p. 113.4°), α-naphthylamine (m.p. 50°), α-naphthol (m.p. 96°), benzene (m.p. 5.5°), 1,4-dioxane (m.p. 12°).

Aniline–phenol system

This system has been studied by many authors with respect to a number of properties [1–8]. In almost all works the presence of chemical interaction in the system is noted, and only some authors draw a conclusion concerning the composition of the compounds formed. Thus, there are indications of the compounds:
$C_6H_5NH_2 \cdot C_6H_5OH$ and $C_6H_5NH_2 \cdot 4C_6H_5OH$. The latter was detected by the e.m.f. method [3,4], moreover in the study of the binary system. When an indifferent solvent is introduced into the system, as the authors indicate, the compound decomposes.

In order to determine whether the compound $C_6H_5NH_2 \cdot 4C_6H_5OH$ is reflected in diagrams of other properties, we carried out a cryoscopic study of the system $C_6H_5NH_2—C_6H_5OH$ and again constructed the liquidus curve with the aim of a more detailed study of the fusibility of solutions rich in phenol. Thermal analysis was carried out visually and polythermally. The molecular weight in benzene solutions (at a concentration of 1.5 moles per 1000 g of $C_6H_6$) was measured by the method of V. V. Udovenko [9]; the change in the freezing temperature of the system $C_6H_5NH_2—C_6H_5OH—C_6H_6$ was studied by the method of Ya. A. Fialkov [10]. The data obtained are shown graphically in the form of a summary diagram (Fig. 1). The maximum (at 50 mol. %) on the liquidus line (curve 3) indicates the formation in the system of the compound $C_6H_5NH_2 \cdot C_6H_5OH$ with m.p. 30.5°. On the diagram $\Delta t^\circ$—composition (curve 1), interaction is not manifested.

possibly because the increase in the number of particles as a result of the dissociation of associated phenol molecules exceeds their decrease upon interaction of the components. The molecular-weight–composition diagram (Fig. 1, curve 2) reflects the presence of chemical interaction in the system, but does not permit an unambiguous conclusion regarding the composition of the compound, since the maximum on the diagram falls at 90 mol.% phenol. It is possible that this maximum is caused by the presence in the system of the compound $\mathrm{C_6H_5NH_2 \cdot 4C_6H_5OH}$, detected by the DTA method, but since this compound dissociates in solution, the maximum proved to be shifted from 80 to 90 mol.% phenol.

Fig. 1. Summary diagram of the properties of the aniline–phenol system.

Quinoline–p-nitrophenol system

The system has been studied with respect to a number of properties [11]. The melting diagram indicates the formation of the compound $\mathrm{C_9H_7N \cdot n{-}C_6H_4NO_2OH}$ with m.p. 89.5°. The authors point to the possibility of the existence in the liquid phase of another, strongly dissociated compound, incapable of crystallization, of composition $\mathrm{C_9H_7N \cdot 2n{-}C_6H_4NO_2OH}$. Attention is drawn to the similarity of the summary diagram of various properties of the system $\mathrm{C_9H_7N{-}n{-}C_6H_4NO_2OH}$ to that constructed by one of us [12] for the system $\mathrm{C_5H_5N{-}C_2H_4O_2}$, where, as in the system $\mathrm{C_9H_7N{-}n{-}C_6H_4NO_2OH}$, the “special” points of most properties occur at 80 mol.% of one of the components. We, as well as other authors [13, 14, 15, 16], indicate the possibility of formation in the system of the compound $\mathrm{C_5H_5N \cdot 4C_2H_4O_2}$. Apparently, in the system $\mathrm{C_9H_7N{-}n{-}C_6H_4NO_2OH}$ the compound $\mathrm{C_9H_7N \cdot 4n{-}C_6H_4NO_2OH}$ is also formed, and not $\mathrm{C_9H_7N \cdot 2n{-}C_6H_4NO_2OH}$, as indicated by the authors. To establish whether this compound exists upon dilution of the system with a solvent and whether it is capable of crystallization, we studied in detail a portion of the liquidus curve (from 70 to 100 mol.% $\mathrm{n{-}C_6H_4NO_2OH}$) of the system $\mathrm{C_9H_7N{-}n{-}C_6H_4NO_2OH}$ and carried out a cryoscopic study (in dioxane). The molecular weight was measured at a concentration of 0.5 mole per 1000 g $\mathrm{C_4H_8O_2}$. The data obtained are presented graphically in Fig. 2. The dashed line gives the liquidus line (curve 3) constructed by other authors [11], and the solid line gives our data.

The results of the investigation (Fig. 2) show that the compound $\mathrm{C_9H_7N \cdot 4n{-}C_6H_4NO_2OH}$ was not reflected in the diagrams obtained by us. On curve 2, molecular weight–composition, only the compound $\mathrm{C_9H_7N \cdot n{-}C_6H_4NO_2OH}$ was found. The compound $\mathrm{C_9H_7N \cdot 4n{-}C_6H_4NO_2OH}$, like $\mathrm{C_5H_5N \cdot 4C_2H_4O_2}$, apparently does not crystallize (curve 3) because of the high viscosity of the solutions, and upon dilution of the system with a solvent it decomposes and therefore is not reflected in the diagrams constructed from cryoscopic data (Fig. 2, curves 1 and 2).

Quinoline–m-nitrophenol system

Since in work [11] data of physicochemical analysis for this system are not given, we studied it cryoscopically (in diox-

in dioxane) and by fusibility (visual-polythermal method). The results obtained are shown graphically in Fig. 3. The maximum on the fusibility line (curve 2) occurs at 66 mole % \(m\)-\(C_6H_4NO_2OH\), which gives grounds for assuming the formation in the system of a rather unstable, crystallizing compound \(C_9H_7N \cdot 2m\)-\(C_6H_4NO_2OH\) (m.p. \(61^\circ\)), which, upon dilution of the system with dioxane, apparently decomposes and therefore does not appear in any way on the diagram \(\Delta t^\circ\)—composition.

The \(\alpha\)-naphthylamine—\(\alpha\)-naphthol system

In studying the fusibility of the system [17, 18], the formation was established of the compound
\(4\alpha\)-\(C_{10}H_7NH_2 \cdot \alpha\)-\(C_{10}H_7OH\) with a congruent melting point of \(43^\circ\). In order to determine whether this compound exists in the melt, we studied the system cryoscopically with respect to viscosity, density, and electrical conductivity at 87 and \(97^\circ\). The measurement results are shown graphically in Fig. 4. The summary diagram of the properties studied (Fig. 4) shows that in the liquid phase there apparently exists only an unstable, noncrystallizing compound \(\alpha\)-\(C_{10}H_7NH_2 \cdot \alpha\)-\(C_{10}H_7OH\) (maxima on the viscosity isotherms—curve 5, its temperature coefficient—curve 4, and the reduced electrical conductivity—curve 2). In the solvent (benzene) the compound most probably decomposes and therefore is not reflected in the diagrams \(\Delta t^\circ\)—composition, constructed from the side of both components (curve 1). The existence of the compound \(4\alpha\)-\(C_{10}H_7 \cdot 4NH_2 \cdot \alpha\)-\(C_{10}H_7OH\), detected by fusibility, was not reflected in the diagrams obtained by us, perhaps because the measurements were carried out at temperatures (87, \(97^\circ\)) far exceeding the melting temperature of the compound (\(43^\circ\)).

Fig. 2. Summary diagram of the properties of the quinoline—\(p\)-nitrophenol system.

Fig. 3. Summary diagram of the properties of the quinoline—\(m\)-nitrophenol system.

Fig. 4. Summary diagram of the properties of the \(\alpha\)-naphthylamine—\(\alpha\)-naphthol system.

Conclusions

1. A physicochemical analysis has been carried out of the systems: aniline–phenol, quinoline–\(p\)-nitrophenol, quinoline–\(m\)-nitrophenol, \(\alpha\)-naphthylamine–\(\alpha\)-naphthol.

2. A complex compound of composition 1:4 apparently exists in the liquid phase only in the binary systems: aniline–phenol, quinoline–\(p\)-nitrophenol.

LITERATURE

1. V. Voano, ZhRFKhO, 48, 76, 1916.
2. Technical Encyclopedia. Handbook of Physical, Chemical, and Technological Quantities, vol. 6, Moscow, 1931.
3. L. P. Kulev, ZhOKh, 5, 1566, 1935.

1. B. V. Tronov and L. P. Kulev, Izv. TPI 64, 3, 1948.

2. A. D. Vinogradova, A. M. Tikhomirova, and N. N. Efremov, Izv. Acad. Sci. USSR, Dept. Chem. Sci. 6, 1037, 1936.

3. V. F. Ust’-Kachkintsev, ZhOKh 7, 2062, 1937.

4. V. V. Udovenko and A. P. Toropov, ZhOKh 10, 11, 1940.

5. V. V. Udovenko and M. I. Usanovich, ZhOKh 10, 17, 1940.

6. V. V. Udovenko, ZhOKh 11, 276, 1941.

7. Ya. A. Fialkov and I. D. Muzyka, Izv. SFKhA 19, 314, 1949.

8. A. D. Kirillova and D. E. Dionis’ev, ZhOKh 23, 1103, 1953.

9. A. S. Naumova, ZhOKh 7, 1222, 1949.

10. L. Swearingen, R. Ross, J. Phys. Chem. 38, 1085, 1934.

11. L. Swearingen, L. Heck, J. Phys. Chem. 38, 395, 1934.

12. L. Swearingen, R. Ross, J. Phys. Chem. 39, 821, 1935.

13. B. Lakshmanan, J. Indian Inst. Sci. A 36, 97, 1954.

14. R. Kremann, Strohschneider, Monatsch. 39, 505, 1918.

15. L. Vignon, Bull. Soc. Chim. Paris 6, 387, 656, 1919.