In situ Fourier transform IR, UV-visible, and gravimetric data were obtained to characterize the single electron transfer reaction of 1,4-dimethoxybenzene (DMOB) on copper-montmorillonite (CuX). Upon dehydration, 0.8 molecule of DMOB is sorbed onto each unit cell of CuX. Sorption of DMOB produces a color change of the DMOB-CuX complex from pale blue to dark green typical of clay-mediated electron transfer reactions. This color change is manifested in the UV-visible spectrum by the growth of three intense bands at 400, 451, and 464 nm, which are in good agreement with published electronic spectra of the DMOB cation. Several vibrational modes of DMOB were significantly perturbed by the formation of the radical cation which include a red-shift of the v19 band from 1509 to 1502 cm-1 and a blue-shift of the j24 h), all of the DMOB and DMOB+ bands were eliminated. These data indicate that the formation of the radical cation is, in fact, reversible and that no significant dimerization or polymerization of DMOB occurs.
An apparatus was built to collect simultaneous gravimetric and Fourier transform infrared sorption/desorption data on self-supporting clay films in a controlled-environment cell. This apparatus enables the masses of several sorbed species to be continuously monitored in situ. Its primary purpose is to characterize physisorption and chemisorption of arenes on clays.
Abstract--Products resulting from the reaction of toluene with Cu(II)-montmorillonite were analyzed using GC/MS, HPLC/MS, GPC, and FTIR methods. Numerous oligomers of toluene were observed, extending at least as high as the resolution limit (1500 g/tool) of the GPC column. The FTIR spectrum of the nonvolatile components of the extract was very similar to that of liquid toluene. GC/MS data on the volatile components revealed dimers, trimers, and a multitude of transmethylated products. Oligomerization proceeded via both ring-ring (i.e., polyphenyl) and ring-methyl linkages. The primary transmethylated products were tert-butylbenzene and isopropylxylene, indicating a competition between ringand side-chain methylations. The side-chain substitutions cannot be explained in terms of the aromatic radical cation intermediate which typically forms in arene/clay reactions. A consideration of alkylbenzene reactions observed in various other media suggests that the present transmethylation reactions occur via a benzyl cation intermediate.
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