resumo
The tetrabutylammonium (TBA) salts of Keggin-type polyoxotungstates of the general formula [XW(11)Fe(III)(H(2)O)O(39)](n-), where X = P, B or Si, were evaluated as catalysts in the oxidation, under mild conditions, of ethylbenzene, cumene, p-cymene and sec-butylbenzene with aqueous H(2)O(2) in CH(3)CN at 80 degrees C. The influence of various factors, such as the substrate/catalyst molar ratio, the amount of oxidant added or the reaction time, was investigated in a systematic way. Generally, the system exhibited moderate conversion, with good selectivity towards the corresponding acetophenone and hydroperoxide. In order to understand the reaction pathways, the oxidation of several products and presumed intermediates was also carried out in the presence of TBA(4)[PW(11)Fe(H(2)O)O(39)]center dot 2H(2)O. Under the conditions used, the oxidation of styrene and styrene derivatives gave rise mainly to carbon carbon double-bond cleavage, affording the corresponding products in very high yields (81-87%). Possible reaction pathways are presented.
palavras-chave
KEGGIN-TYPE POLYOXOTUNGSTATES; SELECTIVE OXIDATION; MOLECULAR-SIEVES; POLYOXOMETALATE; TUNGSTOPHOSPHATES; HYDROCARBONS; COMPLEXES; OXYGEN; ALKYLAROMATICS; CHEMISTRY
categoria
Chemistry
autores
Estrada, AC; Simoes, MMQ; Santos, ICMS; Neves, MGPMS; Cavaleiro, JAS; Cavaleiro, AMV
nossos autores
Ana Cristina Estrada
Investigador Júnior
Ana Maria Vieira Silva Viana Cavaleiro
Professor Catedrático
Isabel Cristina Maia da Silva Santos Vieira
Investigador Júnioragradecimentos
Thanks are due to the University of Aveiro and FCT (Fundacao para a Ciencia e a Tecnologia) for funding. A.C.E. and I.C.M.S.S. also thank FCT for their grants.