Add to ORKGThe present investigation originated with the observation that a t-butylgroup, when substituted in one of the heteroaromatics, thiophene, furan or pyrrole, confers unique stability to these systems toward attack by Lewis-and strong mineral acids. The t-butylheterocycles, in contrast with other alkyl derivatives of these ring systems, resist ringopening and polymerisation reactions in acidic media. A rationalization, based on sterk factors, is given for this phenomenon. We have studied reactions of these aromatic compounds under Friedel-Crafts conditions, e.g. aluminiumchloride and 96% sulfuric acid