ORGN 300 |
| The solid-supported reagent Ce(IV)/SiO2 is an oxidizing agent prepared by adsorbing ceric ammonium nitrate onto the surface of silica gel. Conditions under which crystals of the inorganic reagent form on silica gel instead of the desired thin film were determined through microscopic examination (40-1000 times magnification), including observations with polarized light and experiments involving dynamic interaction of samples of the Ce(IV)/SiO2 reagent with polar and nonpolar liquids. Crystallization is undesirable because ceric ammonium nitrate in the solid phase is unreactive towards heterogeneous chemical reactions. For example, a quantitative yield of 2,5-di-tert-butyl-1,4-benzoquinone is obtained when a CH2Cl2 solution of the corresponding hydroquinone is stirred against the Ce(IV)/SiO2 reagent for 5 min at room temperature; however, no reaction of any kind is observed when the solid-supported reagent is replaced with finely powdered ceric ammonium nitrate, silica gel, or a physical mixture of both. |
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Combinatorial, Parallel, and Solid-Phase Chemistry
1:00 PM-5:20 PM, Tuesday, 28 March 2006 Georgia World Congress Center -- C302, Oral
Division of Organic Chemistry |