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Indexed by:期刊论文

Date of Publication:2010-11-01

Journal:JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL

Included Journals:SCIE、EI、Scopus

Volume:332

Issue:1-2

Page Number:145-151

ISSN No.:1381-1169

Key Words:Phenol; o-Cresol; Catechol; Bronsted acid-catalyzed tert-butylation; Density functional theory

Abstract:SO(3)H-functionalized ionic liquids (FILs) have been used to catalyze the alkylation of phenol, o-cresol and catechol with tert-butyl alcohol (TBA), and the catalytic performances are promising. During these Bronsted acid-catalyzed tert-butylations, t-butyl phenol ether (TBPE) and t-butyl o-cresol ether (TBOCE) are found, but no t-butyl catechol ether (TBCE) is detected. With the help of density functional theory (DFT) calculations, the reaction mechanisms of Bronsted acid-catalyzed tert-butylation of phenol, o-cresol and catechol were examined. The steric effect of t-butyl group does not have an apparent impact on the regioselectivity to t-butyl ether. The differences in the stability of O-alkylation intermediates, resulted from different ortho-substituents, account for the regioselectivity to t-butyl ether. For catechol tert-butylation, an intramolecular hydrogen bond is formed within the O-alkylation intermediate, which leads to extra stability of this intermediate and obvious increase of the activation barrier for TBCE formation. The intramolecular hydrogen bond formed within the O-alkylation intermediate facilitates its isomerization. inhibits the TBCE formation, thus making the reaction kinetics for catechol tert-butylation unique. (C) 2010 Elsevier B.V. All rights reserved.