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With cyclodextrins(α-and β-CD)and sodium carboxymethylamylose(Na-CMA)ashosts,and with H(CF_2)_(12)CO_2K(1),CH_3(CH_2)_(10)CO_2K(2),Cl(CF_2)_8CH_2CH_2N~+Me-3I~-(3),CH_3(CH_2)_(8-)CH_2N~+Me_3I~-(4),CI(CF_2)_(10)CH_2CH_2N+Me_3I~-(5)and CH_3(CH_2)_(10)CH_2N~+Me_3I~-(6)as guest sub-strates,the different behaviors of fluorocarbon and hydrocarbon surfactants have been studied by sur-face tension measurements.Limited cavity size prevents the inclusion of fluorocarbon surfactants byα-CD,but the binding byβ-CD is stronger for the fluorocarbon substrate 3 than that for its hydrocarbonanalog 4.A comparison of the thermodynamic parameters of the β-CD binding process for 3and 6 reveals that for the former the binding is driven by entropy or hydrophobic forces,butfor the latter the process is enthalpy-favored.Notably,Na-CMA fails to bind the fluorocarbonsubstrates.A crucial difference between the cyclodextrins and the amylose-type hosts lies in the factthat the former hosts possess pre-organized cavities whereas the latter have to readjust their confor-mations from loose and extended helices with random coils to interrupted helices during the process ofbinding.Apparently,this extra energy requirement demands contributions from lipophilic interactionswhich do not exist between fluorocarbon chains and the hosts.Thus lipophilic forces are significantin hydrophobic-lipophilic interactions.
With cyclodextrins (α-and β-CD) and sodium carboxymethylamylose (Na-CMA) as hosts, and with H (CF_2) _ (12) CO_2K (1), CH_3 (CH_2) _ (10) CO_2K (3), CH_3 (CH_2) _ (8-) CH_2N ~ + Me_3I ~ - (4), CI (CF_2) _ (10) CH_2CH_2N + Me_3I ~ - CH_3 (CH_2) _ (10) CH_2N ~ + Me_3I ~ - (6) as guest sub-strates, the different behaviors of fluorocarbon and hydrocarbon surfactants have been studied by sur-face tension measurements. Limited cavity size prevents the inclusion of fluorocarbon surfactants by α-CD, but the binding by β-CD is stronger for the fluorocarbon substrate 3 than that for its hydrocarbonanalog 4. A comparison of the thermodynamic parameters of the β-CD binding process for 3 and 6 reveals that for the former the binding is driven by entropy or hydrophobic forces, but for the latter process is enthalpy-favored. Notably, Na-CMA fails to bind the fluorocarbonsubstrates. A crucial difference between the cyclodextrins and the amylose-type hosts lies in the factthat the former hosts possess pre-organized cavities yet the latter have to readjust their confor-mations from loose and extended helices with random coils to disconnected helices during the process ofbinding. Apparently, this extra energy requirement demands contributions from lipophilic interactionswhich do not exist between fluorocarbon chains and the hosts.Thus lipophilic forces are significantin hydrophobic-lipophilic interactions.