calixarenes and 1-4-dioxane

Disinfection byproducts such as trihalomethanes are commonly found in drinking water. Trihalomethanes are formed upon chlorination of natural organic matter found in many drinking water sources. Inspired by molecular CHCl

Topics: Adsorption; Calixarenes; Dioxanes; Drinking Water; Phenylalanine; Polymers; Porosity; Trihalomethanes; Water Pollutants, Chemical; Water Purification

The synthesis of N-benzyl- and N-cyclohexylammonium resorcinarene trifluoroacetate (TFA) and triflate (OTf) salt receptors was investigated. Solid-state analysis by single-crystal X-ray diffraction revealed that the N-alkylammonium resorcinarene salts (NARSs) with different upper substituents had different cavity sizes and different affinities for anions. Anion-exchange experiments by mixing equimolar amounts of N-benzylammonium resorcinarene trifluoroacetate and N-cyclohexylammonium resorcinarene triflate, as well as N-benzylammonium resorcinarene triflate and N-cyclohexylammonium resorcinarene trifluoroacetate showed that the NARS with flexible benzyl groups preferred the larger OTf anion, whereas the rigid cyclohexyl groups preferred the smaller TFA anions. The anion-exchange processes were confirmed in the solid state by single-crystal and powder X-ray diffraction experiments and in the gas phase by electrospray ionization mass spectrometry.

Topics: Anions; Benzylammonium Compounds; Calixarenes; Crystallography, X-Ray; Dioxanes; Mesylates; Models, Molecular; Phenylalanine; Salts; Trifluoroacetic Acid

Oxygen and oxidants enhance the sensitivity of cells to radiation. To understand this effect at the mechanistic level, the redox dependences for the reactivity of weakly reducing alpha-monoalkoxyalkyl radicals of 1,4-dioxane and tetrahydrofuran with a series of oxidants, for example, quinones, viologens, and nitro-arenes, with one-electron reduction potentials E71 values ranging from -80 to -640 mV, have been determined using the technique of pulse radiolysis. The second-order rate constants for these reactions with the alpha-monoalkoxyalkyl radicals of 1,4-dioxane and tetrahydrofuran are in the range (0.03-1.5) x 109 and (1.0-6.6) x 109 dm3 mol(-1) s(-1), respectively. The reactions of the alpha-alkoxyalkyl radicals of 1,4-dioxane with quinones and viologens involve an outer-sphere electron transfer, in contrast to a reaction with the nitro-arenes to give adducts. The resulting long-lived nitroaromatic adduct radicals were found to react with the reductant, TMPD, probably leading to the formation of hydroxylamine-type products. In cells, adducts formed on reaction of deoxyribose sugar radical with oxidants and subsequent reactions with reductants may contribute to the mechanisms involved in radiosensitization by oxygen and those oxidants that interact through adduct formation.

Topics: Calixarenes; Dioxanes; Free Radicals; Furans; Oxidants; Oxidation-Reduction; Quinones; Viologens