Oxidación de hidrocarburos aromáticos en condiciones de catálisis por transferencia de fase

Abstract

The oxidation of alkylaromatic substrates under phase transfer catalysis conditions for obtaining carboxylic and carbonilic derivatives is reported (cetyltrilmethilamonio, MnO₄ -, CH₂Cl₂-H₂O, range of temperatures). Reaction conditions (molar rates and relations of reagents, volumes of reaction mixture, reaction times) are detailed. Cromatographic conditions for detection and increasing the
efficiency of qualitative identification of carboxi- and carbonile derivatives were analyzed by means of thin layer chromatography using silicagel chromatoplates 60G of 0,25 mm of thickness and as developing reagent a 1 % vainilline solution in HClO₄ 50 % or chromato-cameras with vapors of iodine. To identify carboxylic derivatives silicon oxides and aluminum were used in thin layer or mixed with starch, revealing with hydroalcoholic solutions of indicators. For detecting carbonílic compounds silicagel modified with polyethyleneglycol 4000 (30 g SiO₂ + 12 g polyethyleneglycol-4000) was used. Elution is developed with a solvent mixture: CCl₄-ethanol (120 : 1, v/v) and the synthesized compounds revealed with iodine vapors. The experimental data allows to optimize the yield (> 70 %) and the purification process of those derivatives. This procedure inhibits the autocatalytic process of destruction of the KMnO₄ under the reaction conditions and the adsorption of target compounds onto manganese (IV) oxide. The described procedure minimizes the production and volume of residual wastes. An hypothetical mechanism of the oxidation is proposed. The obtained compounds were properly characterized using physical chemical methods, corroborating the proposed structures for generated acids and ketoderivatives.