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Russian Chemical Bulletin, International Edition, Vol. 62, No. 5, pp. 1286—1292, May, 2013

Brief Communications Adsorption and separation of isomeric methyl and dimethylaminoadamantanes on graphitized thermal carbon black S. N. Yashkin, E. A. Yashkina, D. A. Svetlov, and Yu. N. Klimochkin Samara State Technical University, 244 ul. Molodogvardeiskaya, 443100 Samara, Russian Federation. Fax: +7 (846) 278 4400. Еmail: [email protected] The thermodynamic characteristics of adsorption (TCA) of isomeric molecules of methyl and dimethylaminoadamantanes on the surface of the basis face of graphite were determined experimentally and calculated by the molecular statistical method. A relationship between the geometric structure of adsorbate molecules and the values of their TCA on graphitized thermal carbon black was established. The data obtained were used for the gas chromatographic identi fication of the amination products of a mixture of Z,Eisomers of 1,4dimethyladamantane and 1,3dimethyladamantane. Key words: adsorption, isomeric methyl and dimethylaminoadamantanes, graphitized thermal carbon black, molecular statistical calculations.

Due to the unique molecular structure, cage hydro carbons and their derivatives form many diverse geometric and stereoisomers, and some of these compounds are op tical isomers with optical activity caused by the asymme try of a molecular tetrahedron.1 The number of possible isomers increases sharply with an increase in the molecu lar weight. Various types of isomerism in the adamantane system and the possibility of condensation of adamantane fragments followed by particular families of polymantane and polyadamantane hydrocarbons lead to considerable difficulties in their separation and identification. To ad dress these problems, one can use adsorption methods based on the use of adsorbents with surface sensitive even to insignificant differences in geometry of isomers with similar properties.2

This work continues the cycle of our investigations on the regularities of adsorption and structural selectivi ty of the graphitized thermal carbon black (GTC) sur face to adamantane derivatives under the conditions of equilibrium gas adsorption chromatography (GAC).3—6 Among adamantanes the amino derivatives play a signifi cant role because they show a wide range of physiological effects and for this reason found use as highly efficient drugs. In spite of success achieved in chromatographic determination of these groups of substances, the problems of separation and isolation of individual isomers from com plicated synthetic mixtures remain unsolved and exert a negative effect on the quality of the obtained final drugs. The purpose of this work is the experimental and molecu lar statistical investigation of adsorption of isomeric mol

Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1287—1293, May, 2013. 10665285/13/62051286 © 2013 Springer Science+Business Media, Inc.

Separation of aminoadamantanes on graphite

Russ.Chem.Bull., Int.Ed., Vol. 62, No. 5, May, 2013

ecules of methyl and dimethylaminoadamantanes on the GTC surface and the evaluation of selectivity of the car bon black in the separation of the compounds of interest. Isomeric methyl (1—7) and dimethylaminoadaman tanes (8—16), as well as 3,5,7trimethyl1aminoadaman tane (17) and methyl1adamantylmethylamine (18) were studied. Compounds 8 and 18 found practical use as highly efficient drugs with a wide pharmaceutical spec trum known as Memantine and Rimantadine, respectively. Experimental Thermodynamic characteristics of adsorption (TCA) for se lected molecules of methylaminoadamantanes were experimen tally determined under the conditions of equilibrium GAC on a Kristallyuks4000M instrument with a flameionization detec tor in the isothermal regime. A glass micropacked column (1.00 m×1.5 mm) loaded with hydrogentreated GTC (Carbo paсk C НТ) with a carbon black particle diameter of 60—80 mesh and a specific surface area of 10 m2 g–1 (Supelco) was used. Helium served as a carrier gas, and methane was a nonsorbed reference substance. Samples were injected into the chromato graphic column as strongly dilute solutions in nhexane, which was used as an extracting agent when isolating pure aminoada mantanes from alkaline aqueous solutions (3 mol L–1) of their hydrochlorides.3 The volume flow rate of the carrier gas was varied from 25 to 30 cm3 min–1. The temperature of the column ranged from 373 to 473 K with an increment of 10 K. The inaccuracy of the experimental determination of the specific retention volume (VA,1, cm3 m–2) did not exceed 4.5%. The retention volume is

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equal to the adsorption equilibrium constant (Henry constant) K1,C. The molar differential heats of adsorption q–dif,1 (kJ mol–1) – and changes in entropies (S 1,c)s (J mol–1 K–1) of adsorption were determined from the primary chromatographic data us ing a standard procedure.4,7 The inaccuracy of determination – of q–dif,1 and (S 1,c)s was ±1 kJ mol–1 and ±5.0 J mol–1 K–1, respectively. The molecular statistical calculation of Henry constants was performed within the framework of the atomatom approxi mation using a standard procedure, which was repeatedly ap plied in our works on other adamantane derivatives.3—5 The values of atomatom potentials necessary for the molecular sta tistical calculations were taken from literature.3,8 The method of isostructural fragments was used to evaluate the geometric pa rameters of the compounds of interest.8 The experimental and calculated values of TCA are given in Table 1.

Results and Discussion Methylaminoadamantane molecules on the GTC sur face predominantly enter into intermolecular interactions brought about by dispersion forces as indicated by the re lationship q–dif,1 = f(М) close to linear (Fig. 1) and well consistent with our earlier data for methyl, halogen, and hydroxy derivatives of adamantane.10 There are recent re ports that aliphatic amines are capable of interacting with the GTC surface through specific interactions, including hydrogen bonding.11 However, these interactions are evi denced, as a rule, by a series of factors, such as a diffuse back front of the chromatographic peak in the Henry re

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Yashkin et al.

Table 1. Values of TCA of molecules of methyl and dimethylaminoadamantanes on the basis face of graphite over the temperature range 373—493 K obtained experimentally and calculated by the molecular statistical method and using the twodimensional ideal gas modela Adsorbate

lnК1,C 373 К

433 К

493 К

q–dif,1 /kJ mol–1

–

–

–(S 1,c)s I

C s1,p

IIb J mol–1 K–1

3Methyl1aminoadamantane (1)

(4.540) 4.577 1Methyl2aminoadamantane (2) 4.663 2Methyl1aminoadamantane (3) 4.570 cis4Methyl1aminoadamantane (4) 4.226 trans4Methyl1aminoadamantane (5) 4.685 1Methylcis4aminoadamantane (6) 4.218 1Methyltrans4aminoadamantane (7) 4.662 3,5Dimethyl1aminoadamantane (8) (5.574) 5.573 cis2,5Dimethyl1aminoadamantane (9) (5.160) 5.122 trans2,5Dimethyl1aminoadamantane (10) (5.818) 5.871 cis3,6Dimethyl1aminoadamantane (11) 5.441 trans3,6Dimethyl1aminoadamantane (12) 5.658 exo,exo2,4Dimethyl1aminoadamantane (13) 5.490 exo,endo2,4Dimethyl1aminoadamantane (14) 5.472 endo,exo2,4Dimethyl1aminoadamantane(15) 4.682 endo,endo2,4Dimethyl1aminoadamantane (16) 5.959 3,5,7Trimethyl1aminoadamantane (17) (6.319) 6.346 1(1Adamantyl)ethylamine (18) (6.151) 6.172

(2.397) 2.393 2.463 2.391 2.183 2.512 2.168 2.501 (3.221) 3.166 (2.920) 2.857 (3.384) 3.400 3.150 3.324 3.169 3.149 2.544 3.462 (3.750) 3.723 (3.690) 3.673

(0.775) 0.789 0.847 0.794 0.662 0.912 0.643 0.906 — 1.400 — 1.186 — 1.593 1.448 1.585 1.455 1.434 0.956 1.640 (1.806) 1.812 — 1.835

(48.0) 48.1 48.5 47.9 45.3 47.9 45.5 47.7 (52.7) 53.0 (50.2) 50.0 (54.5) 54.3 50.8 51.5 51.3 51.3 47.4 54.8 (57.5) 57.7 (54.9) 55.1 –

(99.2) 99.5 99.8 99.2 94.9 98.1 95.3 97.8 (103.2) 104.3 (99.9) 100.0 (106.0) 105.5 99.4 99.6 100.4 100.7 96.6 106.2 (109.9) 110.1 (104.3) 105.1

— 111.7 111.7 111.7 111.7 111.7 111.7 111.7 — 112.0 — 112.0 — 112.0 112.0 112.0 112.0 112.0 112.0 112.0 — 112.4 — 112.0

— 15.2 15.3 17.0 4.1 13.2 4.3 11.6 — 19.3 — 12.4 — 22.4 6.9 6.2 12.4 12.5 5.9 24.6 — 23.2 — 17.5 –

I are experimental and calculated by the molecular statistical method values of –(S 1,c)s, II are the values of –(S 1,c)s calculated using the twodimensional ideal gas model. The experimental data are given in parentheses. – b The calculation was performed using the formula9: (S 1,c)s = Rln(MТav)0.5 + 56.95 + R, where R = 8.314 J mol–1 K–1, Тav = 433.15 K. a

gion and a relatively high heat of adsorption for substances with a low molecular polarizability. In this work, these specific features of the chromatographic behavior were not observed and, hence, the interaction of aminoada mantanes with the GTC surface seems to be nonspecific in character. This assumption is favored by an analysis of q–dif,1 val ues, which showed that the contribution of the NH2 group of 1 and 2aminoadamantanes to the heat of adsorption is3 6.7 and 7.9 kJ mol–1, respectively. The transition to the corresponding derivative with the nodal СН3 group in creases q–dif,1 by 5.0 kJ mol–1, on the average, which is comparable with the contribution of the methyl group in nalkanes.2 The value of q–dif,1 for 3,5dimethyl1ami noadamantane is intermediate relative to the q–dif,1 values for isomeric cis and trans2,5dimethyl1aminoadaman tanes, respectively (see Table 1). We have earlier observed similar regularities when studying adsorption of isomeric methyladamantanes on graphite.4

A comparison of q–dif,1 and К1,С in the series of methy laminoadamantanes and isostructural methyladaman tanes4 suggests that the adsorption potential of the NH2 group on graphite is slightly larger than that of the СН3 group. The observed differences are probably caused by a higher polarizability of the nitrogen atom. The differ ence in q–dif,1 for the corresponding monoamino and monomethyladamantanes (1.0—2.5 kJ) results in a higher retention of amines compared to their methyl analogs. The data obtained make it possible to evaluate how selective is the response of the graphite surface to differ ences in the structure of stereoisomeric dimethylaminoad amantane molecules. According to our data (see Table 1), there are significant differences in the TCA values for isomeric cis/trans2,5dimethyl1aminoadamantanes, which are well consistent with the earlier obtained results on the separation of a mixture of isostructural cis/trans 1,3,4trimethyladamantanes.4 The separation factor for cis—trans2,5dimethyl1aminoadamantanes at the av



q–dif,1/kJ mol–1 60 7

57 6 54

4

51

5 3

48 2 45 1 19

20.5

22

23.5

M/Å3

Fig. 1. Experimental values of q–dif,1 vs М for 1aminoada mantane (q–dif,1 = 43.7 kJ mol–1) 4 (1), 2aminoadamantane (q–dif,1 = 44.9 kJ mol–1)4 (2), 1amino3methyladamantane (3), 3,5dimethyl1aminoadamantane (4), cis2,5dimethyl1amino adamantane (5), trans2,5dimethyl1aminoadamantane (6), and 3,5,7trimethyl1aminoadamantane (7). The calculation of q–dif,1 was performed using the formula: q–dif,1 = 2.447•М – 0.143; r 2 = 0.981.

erage temperature of the chromatographic experiment is cis/trans = 1.72, which is close to a similar value for 1,3,4trimethyladamantane isomers (cis/trans = 1.98).4 A high structural selectivity of the GTC is observed when the TCA of structural isomers are compared. In particu lar, it follows from the data in Table 1 that the cisisomer of 2,5dimethyl1aminoadamantane more weakly inter acts with the graphite surface and the interaction of the transisomer is stronger, on the contrary, compared to 3,5dimethyl1aminoadamantane Memantine). The sep aration factor for the isomers (Memantine/cis = 1.36 and trans/Memantine = 1.26) indicates the possibility of their almost complete separation on the used micropacked col umn with Carbopack C HT. The established4,10 regularities of adsorption of iso meric alkyladamantanes on the graphite surface are en tirely valid for isomeric alkylaminoadamantanes as well:

1

CH3 CH3

the relative order of elution of the isomers remains un changed when the СН3 group is replaced by the NH2 group. A comparison of the TCA of isostructural alkyl and alkylaminoadamantanes suggests the equilibrium con figuration of adsorbate molecules in the field of adsorption forces of GTC. Let us consider as an example three pairs of compounds: 1,3dimethyladamantane—1, 1,3,5trim ethyladamantane—8, and 1,3,5,7tetramethyladaman tane—17. It is seen that the difference in the q–dif,1 values for the first pair of compounds is 1.7 kJ mol–1, for the second pair it is 1.5 kJ mol–1, and the difference for the third pair is 2.1 kJ mol–1. The q–dif,1 values are close, being 1.8±0.3 kJ mol–1 on the average. Thus, the value of – q dif,1 indicates a certain difference in the adsorption po tential of the СН3 and NH2 groups. In the case of com pounds 1 and 8, there is no uncertainty in the determina tion of arrangement of these molecules in the GTC sur face: the cyclohexane fragment containing the highest number of substituents is localized in the immediate vi cinity of the adsorbent surface. The observed regularity has previously been established in the study of adsorption of a large group of the adamantane derivatives on GTC10 under the conditions of equilibrium GAC. At the same time, in molecule 17 all cyclohexane frag ments contain equal numbers of substituents, and upon adsorption this molecule can adopt one of two positions (Fig. 2): the molecule touches the planar surface by the cyclohexane fragment containing three СН3 groups (type 1) or two СН3 groups and one NH2 group contacts the surface (type 2). Our analysis of the q–dif,1 values unam biguously suggests that orientation of the second type takes place. In other words, two СН3 groups and one NH2 group are near the adsorbent surface once adsorption equilibri um in the 17—graphite system is established. For compounds 1, 17, and 18, the TCA values experi mentally determined and calculated by the molecular sta tistical methods coincide within the gas chromatographic experiment inaccuracy (see Table 1). Such a coincidence is a reliable measure of validity of the performed molecular statistical calculations. Therefore, a comparison of the theoretical TCA values in the series of compounds for which no GAC experiments were carried out can be considered

2

NH2

CH3

1289

CH3

CH3

NH2

CH3

Fig. 2. Equilibrium orientations of a 3,5,7trimethyl1aminoadamantane molecule during adsorption on the basis face of graphite.

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quite correct.8 Let us focus on an analysis of the TCA values of methylaminoadamantanes calculated within the framework of the molecular statistical theory of adsorption. It is known that adsorption on the surface of non specific adsorbents, including that on GTC, is determined by two main factors: molecular polarizability (М) and geometric structure of adsorbed molecules (particularly, the molecular area on the surface in the state of adsorption equilibrium (М)). These factors determine the energy of dispersion interaction, which increases with an increase in the polarizability of adsorbate molecules and decreases monotonically proportionally to their distance from the surface.2 Thus, the differences in the values of free ener gies of adsorption related to the Henry constant of adsorp – tion ((F 1,C)s = –RTlnK1,C), depend directly on the ratio of М to М. The adamantane derivatives described above are struc tural isomers and stereoisomers with similar molecular polarizabilities.12 Therefore, the predominant effect on the retention on GTC in a series of isomers is exerted by pa rameter М and that was shown repeatedly for isomeric derivatives of alkanes,2 adamantane,10 norbornane,13 and other saturated polycyclic compounds.14 A comparative analysis of К1,С values for all investigat ed methylaminoadamantanes С12Н21N allows one to ar range them in the order of increasing К1,С as follows: 15 < 9 < 14  11 < 8  13 < 12 < 10 < 16 < 18. The difference in К1,С for pairs 14 and 11, as well as 8 and 13, are comparable with an inaccuracy of gas chromatographic experiment. The differences in К1,С are due to specific features of spatial arrangement of molecules on the planar graphite surface. In the series of cis/transisomers, the cisisomer is characterized by lower К1,С values, which is well consistent with the earlier established regularities for adsorption of isomeric methyladamantanes on graphite.4 Among stereoisomers С12Н21N, the largest difference in К1,C is observed for pair 9—10 (see Table 1), which direct ly indicates the possibility of their complete separation on columns packed with GTC under the GAC conditions. At the same time, for the pair of stereoisomers 11—12 the values of К1,C and q–dif,1 are close and intermediate be tween the corresponding values for compounds 9 and 10. It can be assumed that for the separation of compounds 11 and 12 it is necessary to use columns with GTC consider ably longer than those used for the separation of a mixture of 9 and 10. Among stereoisomeric 2,4dimethylaminoad amantanes, isomer 15 shows the lowest values of TCA and isomer 16 has the highest TCA values. Compounds 13 and 14 exhibit intermediate TCA values, and the differences in numerical TCA values of these compounds are the small est among all pairs of stereoisomers. It follows from this that isomers 13 and 14 cannot be separated on columns with GTC. The pattern of changing q–dif,1 in the series of studied compounds is analogous, on the whole, to the regularities found for the К1,C values.

Yashkin et al.

In our earlier works on stereoisomeric methyladaman tanes, we proposed to estimate the state of molecules in the field of adsorption forces of graphite by analyzing the difference in equilibrium heat capacities of the adsorbate in the adsorbed state and in the equilibrium gas phase – – (C s1,p) (see Table 1).4 The low values of C s1,p assume that the real state of adsorbate molecules adsorbed in the GTC surface is close to the state of an ideal twodimen sional gas (nonlocalized character of adsorption), since the localization of adsorbed species on the surface and the presence of lateral adsorbate—adsorbate interactions al – ways result in a noticeable increase in C s1,p values.15 –s A detailed analysis of the C 1,p values given in Table 1 made it possible to establish the following regularity: the mole cules having one equilibrium orientation that is the most energetically favorable relative to the planar graphite sur face (for instance, trans4methyl1aminoadamantane) – are characterized by enhanced C s1,p values compared to those without an energetically favorable equilibrium orien tation (cis4methyl1aminoadamantane). Based on the – – physical meaning of the C s1,p value (C s1,p ~ (q–dif,1)/T), one can state that for compounds 1, 2, 3, 5, 7, 8, and 10 the q–dif,1 values are temperaturedependent to a greater extent. It appears that the molecule adsorbed on the pla nar surface experiences a onesided action of adsorption forces, whereas external forces act in all directions in the pore upon dissolution in the volume phase or adsorption. Therefore, an increase in the energy of thermal action during adsorption on GTC can result in a situation when an adsorbed molecule takes orientation substantially less favorable in terms of the energy of adsorption. It was shown4 that for one of possible rotations the transisomer is characterized by interactions with the adsorbent lower in energies, since one of the CH3 groups is far away from the planar surface at a distance considerably exceeding the sum of van der Waals radii of the C atoms of graphite and СН3 group. Additional energy expenses are required to surmount the energy barrier that emerges upon rotation, – which leads to an increase in the corresponding C s1,p values. This assumption is favored by approximately equal contributions to the total interaction energies from the cisisomer (close М values) with different orientations of the adsorbate above the adsorbent surface. Accordingly, the rotation of the molecule relative to the planar surface caused by the temperature increase will not result in a noticeably decrease in the q–dif,1 value. Evidently, a highly symmetric adamantane molecule should be characterized – by the lowest C s1,p value, which was found earlier4 –s (C 1,p(adamantane)  0 J mol–1 K–1). The maximum difference in C–s1,p values observed – for isomers 15—16 (C s1,p = 18.7 J mol–1 K–1) and 9—10 –s (C 1,p = 10.0 J mol–1 K–1) can be related to noticeable distinctions in values of their molecular areas contacting with the basis face of graphite. On the contrary, for pairs – of isomers 11—12 and 13—14 the C s1,p values are



0.7 and 0.1 J mol–1 K–1, respectively, which indicates no differences in orientation of molecules of these compounds relative to the planar graphite surface. Thus, the relative – difference in C s1,p values for stereoisomers close in struc ture can be an additional criterion for the possibility of their gas chromatographic separation on columns packed with GTC. – The above analysis of the C s1,p values is well consis – tent with the (S 1,c)s values carrying information about mobility of adsorbate molecules in the field of adsorbent forces (see Table 1). Let us consider pairs of stereoisomers – for molecules with low C s1,p values at which adsorbate molecules adopt several orientations relative to the sur face, which are energetically similar. It is seen that the – (S 1,c)s values are also lower compared to the corre sponding values obtained for the isomer with higher – C s1,p values. The regularity observed can be explained as follows: when an adsorbed molecule can adopt a number of orientations close in energy of the adsorbate molecule relative to the adsorbent surface, the molecule can per form rotational movements. In this way an additional de gree of freedom is gained and, as a consequence, a de – crease in (S 1,c)s results. The absence or hindering of – this rotation should increase the (S 1,c)s values. The – (S 1,c)s values calculated in the framework of the two dimensional ideal gas model9 are also given in Table 1. It – is seen that the (S 1,c)s values calculated using this mod – el are higher than the experimental (S 1,c)s values and those calculated by the molecular statistical method, and the observed difference exceeds the inaccuracy of experi – mental determination of (S 1,c)s. All this indicates a lim itation imposed on the use of this model for the descrip tion of molecules with the cage structure in the field of forces of the planar graphite surface. The detailed analysis of the TCA of molecules of iso meric dimethylaminoadamantanes performed above has a certain practical significance, since these compounds occur as admixtures when 3,5dimethyl1aminoadaman tane is synthesized.16 The chromatogram of separation of a synthetic mix ture of isomeric dimethylaminoadamantanes on a column with Carbopack C HT obtained by the amination of a mixture of Z,Eisomers of 1,4dimethyladamantane is presented in Fig. 3. The mixture of products contains ste reoisomers 9—10 and 11—12.16 However, similar mass spectral and NMR characteristics of the considered iso mers impose significant limitations on their individual identification. Our molecular statistical calculations made it possible to unambiguously identify the peaks on the presented chromatogram. A comparison of experimental К1,C values obtained for peaks A and С with the results of molecular statistical calculations (see Table 1) directly indicates their inherency to individual isomers 9 and 10. Peak В on the chromatogram can be identified as a signal from an unseparated mixture of isomers 11 and 12. The

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B A

C

20

30

40

t/min

Fig. 3. Chromatogram of separation of a synthetic mixture of the amination products of Z,Eisomers of 1,4dimethyladamantane on a column packed with Carbopack C HT (Т = 453 K).

initial mixture of cis/transisomers of 1,4dimethylada mantane includes 1,3dimethyladamantane and, hence, the amination products can contain isomer 8. Since the К1,C values for compound 8 fall in the ranges of К1,C values for isomers 11 and 12, this forms additional difficulties in the chromatographic separation of isomers 8, 11, and 12 on a column with GTC. The retention time of isomer 8 for its separate elution from the column with GTC coincides within the error of chromatographic experiment with the maximum of peak B. Thus, in spite of a high structural selectivity of the GTC surface, all stereoisomers of Me mantine could not be separated on the used micropacked column with GTC. At the same time, a combined use of the experimental data and results of molecular statistical calculations makes it possible to unambiguously perform the group identification of the compounds. Thus, the position of the amino group and the number and mutual orientation of methyl groups in the adsorbate molecule considerably affects the character of adsorption of isomeric methylaminoadamantanes on the basis face of graphite. The amino group interacting with the GTC sur face has a higher adsorption potential compared to the methyl group. The TCA values calculated by the molecu lar statistical methods can be used for the gas chromato graphic identification of the amination products of a mix ture of Z,Eisomers of 1,4dimethyladamantane and 1,3dimethyladamantane. References 1. E. I. Bagrii, Adamantany: poluchenie, svoistva, primenenie [Adamantanes: Synthesis, Properties, and Application], Nauka, Moscow, 1989, 264 pp. (in Russian).

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2. Ya. I. Yashin, E. Ya. Yashin, A. Ya. Yashin, Gazovaya khro matografiya [Gas Chromatography], TransLit, Moscow, 2009, 528 pp. (in Russian). 3. S. N. Yashkin, O. B. Grigoréva, A. K. Buryak, Russ. Chem. Bull. (Engl. Transl.), 2001, 50 [Izv. Akad. Nauk, Ser. Khim., 2001, 50, 938. 4. S. N. Yashkin, D. A. Svetlov, O. V. Novoselova, E. A. Yash kina, Russ. Chem. Bull., Int. Ed., 2008, 57, 2472 [Izv. Akad. Nauk, Ser. Khim., 2008, 57, 2422. 5. S. N. Yashkin, D. A. Svetlov, B. A. Murashov, Russ. Chem. Bull., Int. Ed., 2010, 59, 1512 [Izv. Akad. Nauk, Ser. Khim., 2010, 59, 1478. 6. S. N. Yashkin, D. A. Svetlov, V. S. Sarkisova, Russ. Chem. Bull., Int. Ed., 2011, 60, 1814 [Izv. Akad. Nauk, Ser. Khim., 2011, 60, 1784. 7. Eksperimentalńye metody v adsorbtsii i molekulyarnoi khrom atografii [Experimental Methods in Adsorption and Molecular Chromatography], Ed. Yu. S. Nikitin and R. S. Petrova, Izdvo Mos. Gos. Univ., Moscow, 1990, 318 pp. (in Russian). 8. A. K. Buryak, Russ. Chem. Rev. (Engl. Transl.), 2002, 71 [Usp. Khim., 2002, 71, 788. 9. A. A. Lopatkin, Ros. Khim. Zh., 1996, 40, 5 Mendeleev Chem. J. (Engl. Transl.), 1997, 41. 10. S. N. Yashkin, O. V. Novoselova, D. A. Svetlov, Zh. Fiz. Khim., 2008, 82, 900 Russ. J. Phys. Chem. (Engl. Transl.), 2008, 82.

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11. V. V. Varfolomeeva, A. V. Terentév, A. K. Buryak, Zh. Fiz. Khim., 2009, 83, 655 Russ. J. Phys. Chem. (Engl. Transl.), 2009, 83. 12. A. N. Vereshchagin, Polyarizuemost´ molekul [Polarizability of Molecules], Nauka, Moscow, 1980, 174 pp. (in Russian). 13. S. N. Yashkin, A. A. Svetlov, D. A. Svetlov, Zh. Fiz. Khim., 2008, 82, 1342 Russ. J. Phys. Chem. (Engl. Transl.), 2008, 82, 1189. 14. A. V. Kiselev, V. I. Nazarova, K. D. Shcherbakova, Chro matographia, 1984, 18, 183. 15. N. N. Avgul´, A. V. Kiselev, D. P. Poshkus, Adsorbtsiya gazov i parov na odnorodnykh poverkhnostyakh [Adsorption of Gases and Vapors on Uniform Surfaces], Khimiya, Moscow, 1975, 384 pp. (in Russian). 16. P. E. Krasnikov, E. V. Golovin, M. Yu. Skomorokhov, A. K. Shiryaev, Yu. N. Klimochkin, Tez. dokl. Mezhdunar. nauch. konf. "Perspektivy razvitiya khimii i prakticheskogo primeneniya alitsiklicheskikh soedinenii" [Proc. International Scientific Con ference "Prospects of Development of Chemistry and Practical Use of Alicyclic Compounds] (Samara, May 25—30, 2004), Samara, 2004, p. 163 (in Russian).

Received October 3, 2012; in revised form April 16, 2013