abstract
The oxidation of anthracene, naphthalene, 1-ethylnaphthalene, and 2-ethylnaphthalene with environmentally benign hydrogen peroxide has been studied in the presence of the tetrabutylammonium salts of iron and manganese mono-substituted Keggin-type polyoxometalates [XW(11)M(H(2)O)O(39)](n-) (X=P, Si, or B, M=Mn(III) or Fe(III)). The reactions were performed under homogeneous conditions at 80 degrees C, using acetonitrile as the solvent. For all the catalysts studied, anthracene was selectively oxidized to 9,10-anthraquinone at 100% conversion in the presence of [BW(11)Mn(H(2)O)O(39)](6-). The oxidation of 1-ethylnaphthalene and 2-ethylnaphthalene occurs mainly at the alkyl substituent, along with the formation of phthalic anhydrides, which resulted from aromatic ring oxidation, with iron substituted anions. Naphthalene could not be oxidized with the conditions used. To understand the reaction pathways, the oxidation of several products was performed in the presence of [PW(11)Fe(H(2)O)O(39)](4-). Under the conditions used, the oxidation of vinylnaphthalene derivatives gave rise to mainly carbon-carbon double-bond cleavage, affording the corresponding naphthaldehydes in high yields (> 67%). Possible reaction pathways are presented and the role of different catalysts is discussed.
keywords
IRON-SUBSTITUTED POLYOXOTUNGSTATES; RADICAL-INITIATED REACTIONS; SELECTIVE OXIDATION; CATALYTIC-OXIDATION; MOLECULAR-SIEVES; PHASE OXIDATION; GAS-PHASE; ANTHRACENE; NAPHTHALENE; OXYGEN
subject category
Chemistry
authors
Estrada, AC; Simoes, MMQ; Santos, ICMS; Neves, MGPMS; Cavaleiro, JAS; Cavaleiro, AMV
our authors
Ana Cristina Estrada
Junior Researcher
Ana Maria Vieira Silva Viana Cavaleiro
Full professor
Isabel Cristina Maia da Silva Santos Vieira
Junior Researcheracknowledgements
Thanks are due to the University of Aveiro, FCT (Fundacao para a Ciencia e a Tecnologia) and FEDER for funding the QOPNA and CICECO. A.C.E. also thanks the FCT for her grant.