The adsorption of 4-substituted benzo-and 5,5¢-disubstituted dibenzocrown ethers from benzene by aerosil A-300 was studied. The ethers included a total of 45 compounds with diphenyl oxide, diphenyl, and diphenyl sulfide fragments. Analysis of the Henry coefficients (K H ) and the extent of desorption, the IR spectra of the adsorbed compounds, and the relationship between their structure and adsorption capacity indicated that all structural fragments of the crown ethers studied interact to some extent with aerosil surface fragments. The number of oxygen atoms in the polyether fragment and the size of the macrocycle are the predominant factors. A large, nonadditive increase in K H is observed in going from pentadentate to hexadentate crown ethers.Crown ethers (CE) have found extensive use in extraction processes, phase transfer catalysis, organic synthesis, analytical chemistry, biology, and medicine due to their unique capacity to form stable complexes with ions and neutral molecules [1]. Interest in CE attached to the surface of inorganic supports is related to the myriad possibilities of the use of such materials as complexing agents, adsorbents, and catalysts (see, for example, [2][3][4][5]). On the other hand, elucidation of the nature of the interaction of macroheterocycles with surfaces such as the silica surface is important for understanding the mechanisms for formation of supramolecular surface compounds including guest-host compounds, hydrates, and hydrogen-bonded complexes as the result of multicentric (polydentate) fixation of the organic adsorbate [6].In order to elucidate the chemical nature of the support surface, Loktev et al.[4] studied the adsorption of dibenzo-18-crown-6 (DB18C6) from chloroform solution on nonporous finely-dispersed (A-300 and AM-1-300 aerosils) and wide-pore (silochrom) silicas and on polymethylsiloxane xerogels (PMS-220, PMS-270, PMS-360, and PMS-610) differing in their porous structure parameters. The effect of the structure of CE on this process was examined in the adsorption of 15-crown-5 (15C5), benzo-15-crown-5 (B15C5), 18-crown-6 (18C6), DB18C6, dicyclohexyl-18-crown-6 (DC18C6), and dibenzo-24-crown-8 (DB24C8) on PMS-270. The greatest adsorption for DB18C6 is found for the most hydrophilic A-300. The adsorption of DB18C6 is reduced by a factor of 1.5 on the hydrophobized analog of A-300, namely, AM-1-300 with the same specific surface. Bidzilya et al. [5] assume that major type of interaction of DB18C6 with the surface of aerosil (AS) and silochrom is hydrogen bonding between the silanol groups and oxygen atoms of the CE cavity. Relative to specific adsorption on PMS-270 at low surface occupancies, the CE studied form the following series: DB18C6 > 18C6 > DB24C8 > DC18C6 > B15C5 > 15C5. This series differs from the previously observed capacity of these CE to form complexes with hydroxyl compounds in CHCl 3 : DC18C6 > 18C6 > DB18C6 > DB24C8 > 15C5 > B15C5. It was concluded that nonspecific dispersion interaction of CE with the PMS xerogels is the predominant factor, and ...