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Chromatographic and topological dependence in tracing of the hydrophobic properties with the selected disubstituted benzenes
MICROCHEMICAL
JOURNAL
32, 198-201
(1985)
Chromatographic and Topological Dependence in Tracing the Hydrophobic Properties with the Selected Disubstituted Benzenes J. SLIWIOK, Insritute
M. BARYSZ, of Chemistry,
B. KOCJAN,
Silesian Received
Universiiy, May
of
AND B. KORCZAK Katowice,
Poland
16, 1983
The performed investigations give evidence of applicability of topological indices to the qualitative estimation of the hydrophobic properties with the selected disubstituted benzene derivatives. 0 1985 Academic Press, Inc.
INTRODUCTION
In our previous paper (9) we discussed the hydrophobic properties of the isomeric ethylphenols and phenylenediamines, taking advantage of dissolving of the above-named compounds on a thin layer with the aqueous solution of new fuchsine, used as a visualizing agent. The obtained results were correlated with the IR spectroscopic data, and also with distributions of the electron net charges in the molecules of the analyzed isomers. The Rekker’s partial hydrophobic constants (8) can hardly be applied in the investigation of the hydrophobic properties with isomers. The aim of this paper is to introduce a correlation between the chromatographically established coefficients of hydrophobic properties on one hand and the topological indices of the analyzed isomers on the other. EXPERIMENTAL
The chromatographic investigations. The ready-made chromatographic glass plates covered with silica gel Kieselgel 60 F,,,, layer thickness 0.25 mm (No. 11846, E. Merck, Darmstadt, F.R.G.), were activated for 30 min at 110°C. A 8:2 (v/v) benzene + acetone mixture was used as the mobile phase. The lo-t.~l aliquots were applied of the 0.5% solutions of ortho-, m&ha-, and para-ethylphenol in benzene. Each chromatogram was developed at a height of 14 cm. The analyzed substances were detected with help of a 0.005% aqueous new fuchsine solution. The obtained chromatographic spots were then planimetrically determined. The results gained from 10 separate determinations are given in Table 1. In the case of phenylenediamines one used the ready-made chromatographic glass plates covered with silica gel Kieselgel G, layer thickness 0.25 mm (No. 5721, E. Merck, Darmstadt, F.R.G.), which were first activated for 30 min at 110°C. A 4: 1:5 (v/v) buthanol-acetic acid-water mixture was used as the mobile phase. The 5-~1 aliquots were applied of the 7.5% solutions of the isomeric phenylenediamines in acetone. The analyzed substances were detected by means of a 0.005% aqueous new fuchsine solution. The results are given in Table 2. 198 0026-265X/85 Copyright All rights
$1.50
8 1985 by Academic Press, Inc. of reproduction in any form reserved.
CHROMATOGRAPHIC
AND TOPOLOGICAL
199
STUDY OF BENZENE
TABLE 1 The Rr Values, the Chromatographic Spot Surface Areas, Coefficients of Hydrophobic Properties, and Topological Indices of the Isomeric Ethylphenols
4
Spot surface area (mm2)
Coeffkient hydrophobic properties, 4
Topological index 2 ” X
0.82 0.74 0.71
173 312 267
4.8 2.2 2.7
1.9824 2.0236 2.0202
Isomer o-Ethylphenol mEthylphenol p-Ethylphenol
Theorethical calculations. Applications of topological indices to predict the chromatographic behavior of different classes of organic compounds have been discussed in several papers (1-4, 6). The connectivity indices m~V (5) are the most interesting among them. The authors of this paper applied the index *xv which appeared much more selective for the differentiation of the isomers ortho, metha, and para than commonly in use lx” (7). *xv were calculated from the expression:
where Sy = .?Y - h is a vertex valency for ith atom, p is the number of valence electrons, h is the number of suppressed H atoms, n, is the number of subgraphs with two adjacent edges and “s” identifies a particular subgraph. Evaluation
of *xv for o-phenylenediamine: NH2 H H
3 4
NH2
0 >3:
3
H
3
3 4
b
3
H
3
o-Phenylenediamine
Graph of o-phenylenediamine together with the vertex valency
TABLE 2 The R, Values, the Chromatographic Spot Surface Areas, Coefficients of Hydrophobic and Topological Indices of the Isomeric Phenylenediamines
Isomer o-Phenylenediamine m-Phenylenediamine p-Phenylenediamine
4
Spot surface area (mm’)
Coefficient of hydrophobic properties, hf
0.64 0.49 0.37
231 353 323
3.2 1.9 2.1
Properties,
Topological index 2X” 1.629 1.6704 1.667
200
All of the distinct
SLIWIOK
ET AL.
subgraphs with two adjacent edges:
2x” = (4.4.3)-‘h + (4.3.3)-5 + (4.4.3)-‘h + (3.4.4)-‘h + (3.4.4)-‘b + (3.4.3)-‘h + (3.3.3)-b + (3.3.3)-b + (3.4.3)-s = 1.629
+ (4.3.3)-‘h
DISCUSSION
The chromatographically established coefficients of hydrophobic properties 10 of the investigated isomers were compared with topological indices. The results dealing with the isomeric ethylphenols are collected in Table 1. The results given in Table 1 show that the least pronounced hydrophobic properties are observed with m-ethylphenol. Due to this the molecules of methaisomer are expected to interact with the molecules of water in comparatively the most efficient way. The topological index of metha-isomer also obtains the highest number value. On the other hand, o-ethylphenol shows the highest coefftcient of hydrophobic properties and the lowest topological index, which allows to assume the least efficient interactions with the molecules of water just with this isomer. In Table 2 one collected the data dealing with hydrophobic properties of the isomeric phenylenediamines and the corresponding topological indices. The results, given in Table 2, confirm the mutual dependence between coefftcients of hydrophobic properties and topological indices, similarly as it was the case with the isomeric ethylphenols. From the results of the chromatographic investigations it comes out that hydrophobic properties of the examined isomeric phenylenediamines can be arranged in the following order: metha < para < ortho The number values of the coeffkients of hydrophobic properties h, show the reciprocal proportionality toward topological indices of the investigated isomers. It should be stressed that both with the isomeric ethylphenols and phenyl-
CHROMATOGRAPHIC
AND TOPOLOGICAL
STUDY OF BENZENE
enediamines the sequence of changes of the hydrophobic sponds with this of topological indices, being as follows:
properties
201 well corre-
metha < para < ortho
The above-discussed facts find an additional confirmation in the results of the spectroscopic investigations (9). The performed investigations give evidence of applicability to topological indices to the qualitative estimation of the hydrophobic properties with the selected disubstituted benzene derivatives. The presented results ground differentiation of the hydrophobic properties with the analyzed isomers, although they do not furnish any explanation of the mechanism of the hydrophobic effect formation. REFERENCES I. Bojarski, J., and Ekiert, L., Relationship between molecular connectivity indices of barbiturates and chromatographic parameters. Chromatogruphia 15, 172-176 (1982). 2. Bonchev, D., Mekenyan, Ov., and PretiC, G., Application of topological indices of isomeric alkylbenzenes. J. Chromatogr. 176, 149-156 (1979). 3. Bonchev, D., and Trinajstic, N., On Topological Characterization of Molecular Branching. Int. J. Quantum Chem. Symp. 12, 293 (1978). 4. Kaliszan, R., Correlation between the retention indices and the connectivity indices of alcohols and methyl esters with complex cyclic structure. Chromatogruphia 9, 529-531 (1979). 5. Kier, L. B., and Hall, L. H., “Molecular Connectivity in Chemistry and Drug Research,” Medicinal Chemistry, Vol. 14. Academic Press, New York, 1976. 6. Papazova, D., Dimov, N., and Bonchev, D., Calculation of gas chromatographic retention indices of isoalkanes based on a topological approach. J. Chromatogr. 188, 297-303 (1980). 7. Randic, M., On characterization of molecular branching. J. Amer. Chem. Sot. 97, 6609-6fjlj (1975). 8. Rekker, R. F., “The Hydrophobic Fragmental Constants.” Elsevier, Amsterdam, 1977. 9. Sliwiok, J., Kocjan, B., and Korczak, B., Chromatographic examination of hydrophobic properties with the isomeric ethylphenols and phenylenediamines. Chromatogruphia, 17, 261-263 (1983). 10. Sliwiok, J., Macioszczyk, A., and Kowalska, T., Chromatographic investigation of the hydrophobic properties of isomeric naphtalene derivatives. Chromatogruphia 14, 138-142 (1981).
JOURNAL
32, 198-201
(1985)
Chromatographic and Topological Dependence in Tracing the Hydrophobic Properties with the Selected Disubstituted Benzenes J. SLIWIOK, Insritute
M. BARYSZ, of Chemistry,
B. KOCJAN,
Silesian Received
Universiiy, May
of
AND B. KORCZAK Katowice,
Poland
16, 1983
The performed investigations give evidence of applicability of topological indices to the qualitative estimation of the hydrophobic properties with the selected disubstituted benzene derivatives. 0 1985 Academic Press, Inc.
INTRODUCTION
In our previous paper (9) we discussed the hydrophobic properties of the isomeric ethylphenols and phenylenediamines, taking advantage of dissolving of the above-named compounds on a thin layer with the aqueous solution of new fuchsine, used as a visualizing agent. The obtained results were correlated with the IR spectroscopic data, and also with distributions of the electron net charges in the molecules of the analyzed isomers. The Rekker’s partial hydrophobic constants (8) can hardly be applied in the investigation of the hydrophobic properties with isomers. The aim of this paper is to introduce a correlation between the chromatographically established coefficients of hydrophobic properties on one hand and the topological indices of the analyzed isomers on the other. EXPERIMENTAL
The chromatographic investigations. The ready-made chromatographic glass plates covered with silica gel Kieselgel 60 F,,,, layer thickness 0.25 mm (No. 11846, E. Merck, Darmstadt, F.R.G.), were activated for 30 min at 110°C. A 8:2 (v/v) benzene + acetone mixture was used as the mobile phase. The lo-t.~l aliquots were applied of the 0.5% solutions of ortho-, m&ha-, and para-ethylphenol in benzene. Each chromatogram was developed at a height of 14 cm. The analyzed substances were detected with help of a 0.005% aqueous new fuchsine solution. The obtained chromatographic spots were then planimetrically determined. The results gained from 10 separate determinations are given in Table 1. In the case of phenylenediamines one used the ready-made chromatographic glass plates covered with silica gel Kieselgel G, layer thickness 0.25 mm (No. 5721, E. Merck, Darmstadt, F.R.G.), which were first activated for 30 min at 110°C. A 4: 1:5 (v/v) buthanol-acetic acid-water mixture was used as the mobile phase. The 5-~1 aliquots were applied of the 7.5% solutions of the isomeric phenylenediamines in acetone. The analyzed substances were detected by means of a 0.005% aqueous new fuchsine solution. The results are given in Table 2. 198 0026-265X/85 Copyright All rights
$1.50
8 1985 by Academic Press, Inc. of reproduction in any form reserved.
CHROMATOGRAPHIC
AND TOPOLOGICAL
199
STUDY OF BENZENE
TABLE 1 The Rr Values, the Chromatographic Spot Surface Areas, Coefficients of Hydrophobic Properties, and Topological Indices of the Isomeric Ethylphenols
4
Spot surface area (mm2)
Coeffkient hydrophobic properties, 4
Topological index 2 ” X
0.82 0.74 0.71
173 312 267
4.8 2.2 2.7
1.9824 2.0236 2.0202
Isomer o-Ethylphenol mEthylphenol p-Ethylphenol
Theorethical calculations. Applications of topological indices to predict the chromatographic behavior of different classes of organic compounds have been discussed in several papers (1-4, 6). The connectivity indices m~V (5) are the most interesting among them. The authors of this paper applied the index *xv which appeared much more selective for the differentiation of the isomers ortho, metha, and para than commonly in use lx” (7). *xv were calculated from the expression:
where Sy = .?Y - h is a vertex valency for ith atom, p is the number of valence electrons, h is the number of suppressed H atoms, n, is the number of subgraphs with two adjacent edges and “s” identifies a particular subgraph. Evaluation
of *xv for o-phenylenediamine: NH2 H H
3 4
NH2
0 >3:
3
H
3
3 4
b
3
H
3
o-Phenylenediamine
Graph of o-phenylenediamine together with the vertex valency
TABLE 2 The R, Values, the Chromatographic Spot Surface Areas, Coefficients of Hydrophobic and Topological Indices of the Isomeric Phenylenediamines
Isomer o-Phenylenediamine m-Phenylenediamine p-Phenylenediamine
4
Spot surface area (mm’)
Coefficient of hydrophobic properties, hf
0.64 0.49 0.37
231 353 323
3.2 1.9 2.1
Properties,
Topological index 2X” 1.629 1.6704 1.667
200
All of the distinct
SLIWIOK
ET AL.
subgraphs with two adjacent edges:
2x” = (4.4.3)-‘h + (4.3.3)-5 + (4.4.3)-‘h + (3.4.4)-‘h + (3.4.4)-‘b + (3.4.3)-‘h + (3.3.3)-b + (3.3.3)-b + (3.4.3)-s = 1.629
+ (4.3.3)-‘h
DISCUSSION
The chromatographically established coefficients of hydrophobic properties 10 of the investigated isomers were compared with topological indices. The results dealing with the isomeric ethylphenols are collected in Table 1. The results given in Table 1 show that the least pronounced hydrophobic properties are observed with m-ethylphenol. Due to this the molecules of methaisomer are expected to interact with the molecules of water in comparatively the most efficient way. The topological index of metha-isomer also obtains the highest number value. On the other hand, o-ethylphenol shows the highest coefftcient of hydrophobic properties and the lowest topological index, which allows to assume the least efficient interactions with the molecules of water just with this isomer. In Table 2 one collected the data dealing with hydrophobic properties of the isomeric phenylenediamines and the corresponding topological indices. The results, given in Table 2, confirm the mutual dependence between coefftcients of hydrophobic properties and topological indices, similarly as it was the case with the isomeric ethylphenols. From the results of the chromatographic investigations it comes out that hydrophobic properties of the examined isomeric phenylenediamines can be arranged in the following order: metha < para < ortho The number values of the coeffkients of hydrophobic properties h, show the reciprocal proportionality toward topological indices of the investigated isomers. It should be stressed that both with the isomeric ethylphenols and phenyl-
CHROMATOGRAPHIC
AND TOPOLOGICAL
STUDY OF BENZENE
enediamines the sequence of changes of the hydrophobic sponds with this of topological indices, being as follows:
properties
201 well corre-
metha < para < ortho
The above-discussed facts find an additional confirmation in the results of the spectroscopic investigations (9). The performed investigations give evidence of applicability to topological indices to the qualitative estimation of the hydrophobic properties with the selected disubstituted benzene derivatives. The presented results ground differentiation of the hydrophobic properties with the analyzed isomers, although they do not furnish any explanation of the mechanism of the hydrophobic effect formation. REFERENCES I. Bojarski, J., and Ekiert, L., Relationship between molecular connectivity indices of barbiturates and chromatographic parameters. Chromatogruphia 15, 172-176 (1982). 2. Bonchev, D., Mekenyan, Ov., and PretiC, G., Application of topological indices of isomeric alkylbenzenes. J. Chromatogr. 176, 149-156 (1979). 3. Bonchev, D., and Trinajstic, N., On Topological Characterization of Molecular Branching. Int. J. Quantum Chem. Symp. 12, 293 (1978). 4. Kaliszan, R., Correlation between the retention indices and the connectivity indices of alcohols and methyl esters with complex cyclic structure. Chromatogruphia 9, 529-531 (1979). 5. Kier, L. B., and Hall, L. H., “Molecular Connectivity in Chemistry and Drug Research,” Medicinal Chemistry, Vol. 14. Academic Press, New York, 1976. 6. Papazova, D., Dimov, N., and Bonchev, D., Calculation of gas chromatographic retention indices of isoalkanes based on a topological approach. J. Chromatogr. 188, 297-303 (1980). 7. Randic, M., On characterization of molecular branching. J. Amer. Chem. Sot. 97, 6609-6fjlj (1975). 8. Rekker, R. F., “The Hydrophobic Fragmental Constants.” Elsevier, Amsterdam, 1977. 9. Sliwiok, J., Kocjan, B., and Korczak, B., Chromatographic examination of hydrophobic properties with the isomeric ethylphenols and phenylenediamines. Chromatogruphia, 17, 261-263 (1983). 10. Sliwiok, J., Macioszczyk, A., and Kowalska, T., Chromatographic investigation of the hydrophobic properties of isomeric naphtalene derivatives. Chromatogruphia 14, 138-142 (1981).