Abstract
While H2O2 is a powerful oxidant, decomposing into environmentally benign H2O and O2, a catalyst is often required for reactions with H2O2 to proceed at synthetically useful rates. Organotellurium and organoselenium compounds catalyze the oxidation of halide salts to hypohalous acids using H2O2. When sequestered into xerogel monoliths, the xerogel-chalcogenide combinations have demonstrated increased catalytic activity relative to the organochalcogen compound alone in solution for the oxidation of halide salts to hypohalous acids with H2O2. Diorganotellurides, diorganoselenides, and diorganodiselenides bearing triethoxysilane functionalities were sequestered into xerogel monoliths and their catalytic activity and longevity were investigated. The longevity of the catalyst-xerogel combinations was examined by isolating and recycling the catalyst-xerogel combination. It was found tellurium-containing catalyst 3 and selenium-containing catalyst 8 maintained their catalytic activity through three recycling trials and adding electron-donating substituents to catalyst 3 also increased the catalytic rate. The presence of organotellurium and organoselenium groups in the +4 oxidation state was determined by X-ray photoelectron spectroscopy.
Highlights
The use of H2O2 as an oxidant relative to other oxidizing agents has attracted a great deal of attention due to the advantages of using the environmentally benign H2O2, which decomposes into water and oxygen [1]
The xerogel provides a porous material that can create local environments of higher reaction concentrations than bulk solutions, which may increase the rate of oxidation of halide salts with H2O2
The presence of organotellurium and organoselenium groups in the +4 oxidation state was determined by X-ray photoelectron spectroscopy
Summary
The use of H2O2 as an oxidant relative to other oxidizing agents has attracted a great deal of attention due to the advantages of using the environmentally benign H2O2, which decomposes into water and oxygen [1]. Selenoxides [11,12,13] arylseleninic acids [14,15], and diorganotellurides [16,17,18] are effective catalysts with H2O2 for the oxidation of halide salts. These reactions proceed at ambient conditions to form hypohalous acid, which can be used as a halogenating agent. This procedure offers a less hazardous, more environmentally friendly alternative to the use of other halogenating agents such as elemental bromine. The xerogel provides a porous material that can create local environments of higher reaction concentrations than bulk solutions, which may increase the rate of oxidation of halide salts with H2O2
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