Clay complexes neutral organic molecules

Clay complexes with organic cations may absorb neutral organic molecules in the interlayer space. This process is accompanied by a separation of the silicate layers and, generally, with a change of orientation of the organic cation. Thus, adsorption of benzene or chlorobenzene in pyridinium-montmorillonite changes the disposition of the pyridinium ion from parallel to normal to the silicate layers, and an increase of from 1.25 to 1.50 nm is observed. IR studies of the dichroism of specific IR absorption bands show that the pyridinium cations have their N—H groups directed to the layer surface (C2 axis perpendicular to the layers). For chlorobenzene, the molecules also adopt a perpendicular orientation but with the C—Cl bond axis (C2 axis) parallel to the layers (30). 

The chemical behavior of clays is also mimicked by the title complexes in two respects the presence of cation-exhange capabilities and the reduced water content in the ammonium salt [20]. Currently, other similarities between clays and the water-soluble calixarenes are being probed. In particular, the size- and polarity-selective cavity of the calix[4]arene sulfonates is finding utility in the separation of organic substances, cations, anions, and neutral molecules, from aqueous feed streams. 

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