Electrophilic aromatic substitution reactions of veratrole were studied by a combination of experimental kinetic isotope effects (KIEs), standard theoretical calculations, and dynamic trajectory calculations. The acylation of veratrole with acetyl chloride using aluminum chloride exhibits an inverse intramolecular 12C/13C kinetic isotope effect of 0.990-0.991 and an intermolecular isotope effect of unity. However, the acylation of veratrole using silver perchlorate showed an intramolecular and an intermolecular 12C/13C kinetic isotope effect of unity. These differences in the KIE suggests that the nature of the active electrophile has changed with the differing catalysts. In addition, product ratios were measured for the acylation of butyl phenyl ether in order to see if a change in the catalyst affects the product distribution, and it was found that the product ratios change significantly with the change in catalyst. These results are inconsistent with the conventional mechanism, and they implicate dynamic control of the regioselectivity subsequent to the rate-limiting step.

Kinetic isotope effects and dynamics for Friedel-Crafts acylation

251st National Meeting (2016)

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