文档介绍：Advances in Environmental Research 4Ž. 2000 307᎐312
An investigation of a Friedel-Crafts alkylation reaction
in homogeneous supercritical CO2 and under
subcritical and splitphase reaction conditions
John E. Chateauneuf U, Kan Nie
Department of Chemistry, Western Michigan Uni¨ersity, Kalamazoo, MI 49008, USA
Accepted 20 March 2000
Abstract
This study investigates the Friedel-Crafts alkylation reaction of triphenylmethanol with methoxybenzeneŽ. anisole
in supercritical and subcritical carbon dioxide, and under two-phaseŽ. gasrliquid reaction conditions at moderate
pressures and temperatures. The reaction was initiated using trifluoroacetic acid to produce triphenylmethlycarboca-
tion as the reaction intermediate. Isolated product yields of the Friedel-Crafts product, p-methoxy-
tetraphenylmethane, are reported. ᮊ 2000 Elsevier Science Ltd. All rights reserved.
Keywords: Friedel-Crafts reaction; Carbocation; Supercritical CO22 ; Subcritical CO ; Green chemistry
1. Introduction troscopy. We specifically investigated the pressure, and
corresponding solvent density, dependence of the abso-
In recent investigations of electron transfer reactiv- lute reactivity of electron transfer between excited-state
ity of excited-state carbocations in supercritical carbon 9-phenylxanthenium cation and toluene, as the elec-
tron donorŽ Jin and Chateauneuf, 1999; Jin et al., in
dioxideŽ. SC CO2 , we have demonstrated that stabilized
carbocations, . triphenylmethyl cation, xanthenium preparation. . During these experiments we noticed that
cation and 9-phenylxanthenium cation, could be gener- in the presence of toluene the ground state of the
ated from their corresponding alcohols in CO2 under carbocation was slowly being consumed. This observa-
mildly acidic conditionsŽ. Jin, 1999 . In situ UV-visible tion suggested the possibility that an aromatic
spectroscopy demonstrated that under these conditions -Crafts alkylation reaction was occurring un