Thiophene derivatives in aqueous

Two excellent reviews <71AHC(13)235, 72IJS(C)(7)6l) have dealt with quantitative aspects of electrophilic substitution on thiophenes. Electrophilic substitution in the thiophene ring appears to proceed in most cases by a mechanism similar to that for the homocyclic benzene substrates. The first step involves the formation of a cr-complex, which is rate determining in most reactions in a few cases the decomposition of this intermediate may be rate determining. Evidence for the similarity of mechanism in the thiophene and benzene series stems from detailed kinetic studies. Thus in protodetritiation of thiophene derivatives in aqueous sulfuric and perchloric acids, a linear correlation between log k and —Ho has been established the slopes are very close to those reported for hydrogen exchanges in benzene derivatives. Likewise, the kinetic profile of the reaction of thiophene derivatives with bromine in acetic acid in the dark is the same as for bromination of benzene derivatives. The activation enthalpies and entropies for bromination of thiophene and mesitylene are very similar. 

The self-assembly of supramolecular structures such as host-guest inclusion complexes has r ently bem the focus of a number of research efforts. This approach allows the d ign and building of nanoscale molecular device. It constitutes a conveni t route to realizing the polymerization of hydrophobic molecules (guests) such as thiophene derivatives in aqueous soluticm by using CDs (hosts) and to customizing the polymer ardiitectures 9-11). 

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