Cavity-containing compounds

Of all the cavity-containing compounds, it is perhaps the cyclodextrins that provide the best basis for the construction of small(ish) molecule enzyme mimics. See Section 6.3 for an introduction to... 

Molecules come in all shapes and sizes, but those with concave surfaces1 11 (Fig. 1) have been of a special interest to chemists. In the early 1980s,12 Cram noted a paucity of cavity-containing compounds, dubbing them cavitands... 

Phosphate-substituted zeolites have attracted commercial interest in the past two decades and it is claimed that incorporation of P increases the efficiency of these cavity-containing compounds both as catalysts and as sequestering agents for Ca + and Mg-+. Although in some cases these compounds are silicates with cavity-occluded orthophosphate groups (i.e. silicate/phosphates), in others the phosphate is incorporated in the silicate framework to form genuine silicophosphates with Si-O-P linkages. An important silicate/phosphate cavity structure is NASICON (Section 12.20). 

Hydrates are solid structures composed of water molecules joined as crystals that have a system of cavities. The structure is stable only if at least one part of the cavities contains molecules of small molecular size. These molecules interact weakly with water molecules. Hydrates are not chemical compounds rather, they are clathrates . 

In relation to separation of nucleotides, Hoffman61 found that adenine nucleotides interacted most strongly with cycloheptaamylose, presumably by inclusion of the base within the cavity of cyclodextrin. When epichlorohydrin-cross-linked cycloheptaamylose gel was used as a stationary phase for nucleic acid chromatography, adenine-containing compounds were retarded most strongly. 

Polymerization of triphenylmethyl methacrylate in the presence of a chiral anion catalyst results in a polymer with a helical structure that can be coated onto macroporous silica [742,804). Enantioselectivity in this case results from insertion and fitting of the analyte into the helical cavity. Aromatic compounds and molecules with a rigid nonplanar structure are often well resolved on this phase. The triphenylmethyl methacrylate polymers are normally used with eluents containing methanol or mixtures of hexane and 2-propanol. The polymers are soluble in aromatic hydrocarbons, chlorinated hydrocarbons and tetrahydrofuran which, therefore, are not suitable eluents. 

Measuring Vulcanization. The formation of a three-dimensional structure during vulcanization increases the stiffness (modulus) of the compound. Therefore, following the modulus increase versus cure time provides a continuous picture of the vulcanization process. Oscillating disk rheometers provide a useful method to do this (17). In this test, a preweighed sample of uncured mbber is placed into a preheated cavity containing a conical rotor. The cavity is closed and the rotor is set to oscillate within the mbber sample. As vulcanization proceeds, the compound s resistance to rotor movement increases and this resistance is followed as a function of time, thereby generating a continuous profile of cure behavior. These cure curves,... 

Compounds which have interior cavities which are large enough to incarcerate organic guest molecules have been named molecular container compounds. 

Over the last decade there has been growing interest in the interaction of dmgs with one group of container compounds, the a-, and y-cyclodextrins (cyclic D-glucose oligomers) and their now myriad derivatives. The cyclodextrin molecules have cyclic stmcmres with internal diameters of 0.6-1 nm (see section 5.6). The interior cavity of the cyclodextrin... 

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