Thermodynamic parameters of adsorption of adamantane and its derivatives on graphitized thermal carbon black

The adsorption equilibrium constants for adamantane, 1-fluoro-, 1-chloro-, 1,3-difluoro-, 1,3-dichloro-, 1,3-dibromo-, and 1-hydroxyadamantane, and methyl 1-adamantyl ketone were determined by gas chromatography. The results were compared with molecular statistical calculations based on the known atomic-atomic potentials of the interaction of atoms of the sorbate molecule with the C atom of graphitized thermal carbon black (GTCB). The experimental adsorption heats exceed the calculated values by 3-10 kJ mol^-1. The reasons for this divergence are discussed. The changes in the adsorption entropy show that the molecules of the studied compounds form a layer of the ideal dimeric gas on the GTCB surface upon adsorption.     

Experimental and molecular statistical study of alkyladamantane adsorption on graphitized thermal carbon black

Experimental measurements and molecular statistics methods were used to calculate thermodynamic characteristics of adsorption (TCA) of alkyladamantanes of different structure on the surface of hydrogen-treated graphitized thermal carbon black (GTCB) Carbopack C HT. High selectivity of separation of isomeric alkyladamantanes on GTCB is due to specific features of their geometry and electronic structure. The influence of the spatial structure of adsorbates on the TCA was established. Special attention was given to analysis of the heat capacities of adsorption. The best agreement between the experimental TCA and those calculated by the molecular statistics methods is achieved when the “cage effect“ in the adamantane ring is taken into account. The corresponding corrections are introduced into the parameters of the atom-atomic potential function of pair intermolecular interaction of the Me groups with the carbon atoms of the basal face of graphite, which are localized in the nodal positions of the lattice. The critical parameters for a large group of alkyladamantanes were calculated in terms of the additive group Lydersen method. A set of various topological indices used further for constructing structure-retention correlations on GTCB was obtained.     

Molecular statistical calculation of thermodynamic characteristics of adsorption of O-, S-, and Se-containing heteroadamantanes on graphitized thermal carbon black

The thermodynamic characteristics of adsorption (TCA) on the basal face of graphite have been calculated in terms of the semiempirical molecular statistical theory of adsorption for molecules of O-, S-, and Se-containing heteroadamantanes of different structure and isostructural cyclohexane derivatives. The influence of the nature, number, and position of heteroatoms in the adamantane framework on the TCA values was studied in detail, which made it possible to predict the retention of the compounds considered on the surface of graphitized thermal carbon black under the conditions of equilibrium gas adsorption chromatography. The introduction of each subsequent heteroatom into a polyheteroadamantane molecule makes a non-additive contribution to the TCA values. The contributions of various fragments to the total adsorption energy were calculated by the TCA of isostructural heterocyclohexane molecules, and the most preferential orientations of the framework molecules of the adsorbates relative to the planar graphite surface were determined.     

Gas chromatographic investigation of adsorption equilibria on graphitized thermal carbon black

Summary Retention volumes and heats of adsorption at low surface coverages of graphitized thermal carbon black (GTCB) for C₆–C₁₄ aromatic hydrocarbons have been determined. The dependence of heats of adsorption of these molecules on their structure and the number of carbon atoms in the molecule have been investigated. Substitution in the ring in methylbenzenes is not equivalent to the lengthening of the side-chain in the isomers of n-alkylbenzenes and gives rise to a much greater increase in the retention volumes and heats of adsorption.     

The cell effect in adamantane adsorption on graphitized thermal carbon black

Nonequivalence of the nodal and bridging carbon atoms of the adamantane molecule during adsorption on graphitized thermal carbon black was shown. The nonequivalence is related to a special type of intermolecular interaction, the cell effect. Based on the experimental data and the molecular statistical calculations of Henry's constants, the parameters of atomatom potentials for the nodal carbon atoms in the adamantane molecule were found. This atom-atom potential differs from that known for the carbon atom in the sp³-hybridization. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 849–853, May, 2000.     

Thermodynamic parameters of adsorption of isomeric chloronaphthalenes on graphitized thermal carbon black

Henry's constants and the heats of adsorption of isomeric chloronaphthalenes on graphitized thermal carbon black were calculated by the semiempirical molecular statistical method. The calculated data were compared with experimental results. The best agreement was achieved when corrections for the interaction of the Cl atom with the C atom of the adjacent benzene ring and the presence of other Cl atoms inortho-positions are introduced in calculations of the atom-atomic potential. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 8, pp. 1484–1489, August, 1999.     

A study of adsorption of some bicyclo [2.2.1] heptane derivatives on graphitized thermal carbon black

Retention volumes at zero sample size (Henry's constants of adsorption equilibrium), Kovats' indices and the changes in differential molar internal energy and entropy upon adsorption are found for bicyclo[2.2.1] heptane (norbornane), six isomeric dimethylnorbornanes and 7,7′-bisnorbornane by gas adsorption chromatography on packed columns with GTCB. A molecular statistical calculation of the thermodynamic characteristics of adsorption is carried out and the results are compared with experimental data.     

Experimental and molecular-statistical investigation of adsorption of aminoadamantanes on graphitized thermal carbon black

Thermodynamic characteristics of adsorption of some isomeric aminoadamantanes on graphitized thermal carbon black were determined by molecular-statistic calculations and gas-chromatographic measurements. The parameters of the potential function for the pairwise intermolecular interactions between nitrogen in saturated amines and carbon in graphite were calculated. The best agreement between the experimental and calculated Henry constants for 1-aminoadamantane is attained by introducting a correction taking into account the influence of the cage effect on -substituents in the adamantane unit in the parameters of the _N...C(GTCB) atom-atom potential.     

Calculation of henry constants for the adsorption of isomeric phenylenediamines on graphitized thermal carbon black

Henry constants for the adsorption of o- and p-phenylenediamines on the surface of graphitized thermal carbon black within the temperature range 433–479 K were calculated by the molecular statistical method. The parameters of the atom-atom potential function of intermolecular interaction between the nitrogen atom in aniline and isomeric phenylenediamines and the carbon atom of the basal face of graphite were determined. It was shown that an intramolecular H bond influenced the geometry and adsorption properties of o-phenylenediamine.     

Adsorption of molecules of different structure on graphitized thermal carbon black IV. Gas chromatographic investigation of adsorption of aldehydes,ketones and alcohols on hydrogen-treated graphitized thermal carbon black

Summary Retention volumes (Henry constants) and differential molar change of internal energy at low surface coverages on hydrogen-treated graphitized thermal carbon black (HTGTCG) for aldehydes, ketones and alcohols have been determined. An additional hydrogen treatment of graphitized thermal carbon black at 1000°C (GTCB) was undertaken to remove chemical inhomogeneity of the surface. After this treatment the peaks of oxygenated hydrocarbon derivatives became more symmetrical. Reduction of retention volumes after this treatment was observed only for substances with short hydrocarbon chains. The dependence during adsorption on the structure of, and number of carbon atoms in, aldehydes, ketones and alcohols has been investigated. The Kovats' indices for the chromatography on HTGTCB were obtained and used for identification.     

Thermodynamic characteristics of adsorption of nitrogen-containing heterocycles on graphitized thermal carbon black derived from molecular statistical calculation. 1. Azines

Thermodynamic characteristics of adsorption (TCA) for six-membered aromatic nitrogen-containing heterocycles (azines), viz., pyridine, pyridazine, pyrimidine, and 1,3,5-triazine, on graphitized thermal carbon black (GTC) were experimentally determined and theoretically calculated. The best coincidence of the experiment and calculation is achieved using atom-atomic potential functions of intermolecular interactions, which allow for a decreased -electron density in the aromatic system. The N atoms in the azine molecules are nonequivalent in terms of the adsorption behavior. The GTC surface very selectively adsorbs azines with different molecular structures, and this selectivity can be used for separation and chromatographic analysis of these compounds. The dependence of TCA of azines on the degree of aromaticity of their molecules has been established for the first time.     

Adsorption of cyclic amines on graphitized thermal carbon black

Thermodynamic characteristics of adsorption (TCA) for aniline and its methyl derivatives on the surface of graphitized thermal carbon black (GTC, Carbopack C HT trade mark) were determined using equilibrium gas adsorption chromatography in the range of the lowest adsorbate concentrations in the gas phase. A series of relationships relating the TCA of the studied amines to their physicochemical parameters was obtained. The theoretical values of entropy of adsorption were calculated in the framework of the model of two-dimensional ideal gas and compared with the corresponding experimental values, which allowed one to reveal specific features of the molecular structure of the adsorbates. A similarity between the thermal component of entropy of the studied compounds in the adsorbed state and that of the entropy of the pure liquid adsorbates made it possible to refine the physical state and mobility of the adsorbate molecules in the force field of the adsorbent. The regression equation relating the heats of adsorption on the GTC to such molecular constants of adsorbates as polarizability, molecular surface area, and molecular weight were proposed for the first time. A high predictive power of the equations derived in the work for the preliminary estimation of the adsorption characteristics of alkylanilines and alkylbenzenes on the GTC was shown.     

Adsorption of adamantanol isomers on graphitized thermal carbon black

The thermodynamic characteristics of adsorption of some adamantanol isomers on graphitized thermal carbon black were calculated and determined experimentally. The parameters of the potential function for the intermolecular interaction between hydroxyl oxygen and carbon of the graphite basis plane were determined for the first time. The adsorption properties of adamantanols are largely determined by electron density distribution in the adamantane cage, which are related to the cage effect.     

Calculation of heat adsorption of certain halomethanes on graphitized thermal black

Initial heats of adsorption of a number of halomethanes on graphite have been calculated by a semiempirical molecular-statistical method and from the proportionality of the heat of adsorption to critical parameters of the adsorbate. The results from these calculations are in satisfactory agreement with each other and with the available experimental data.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1721–1723, August, 1989.