Stacking Interactions Between Parallel-Displaced Heterocyclic Aromatic Rings and Substituted-Benzene: Experimental Study in Chloroform

by Wekesa, Francis S

Abstract (Summary)
A series of triptycene-derived scaffold bearing a substituted-benzene and a heterocyclic aromatic ring were synthesized and the ratios of the syn and anti conformers were determined by variable temperature NMR spectroscopy. The syn conformer allows the attached aromatic ring and the heterocycle to interact with each other in the parallel-displaced orientation while the anti conformer does not. The free energy values derived from the equilibrium between the syn and anti isomers in chloroform range from positive (0.4 kcal/mol) to considerably negative (-1.0 kcal/mol). The interactions between a pyrimidine ring and a substituted benzene ring exhibit the highest attraction when the substituent is a strong electron-donating group (EDG), while the interactions between a pyridine ring and a substituted benzene ring show the opposite trend. Mainly repulsive interactions were observed between the benzene rings with EDG and the five-membered heterocycles (furan, pyrrole, and thiophene). Those interactions become slightly attractive when the benzene substituent is an EWG
Bibliographical Information:


School:Miami University

School Location:USA - Ohio

Source Type:Master's Thesis



Date of Publication:01/01/2007

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