Question

Dipole moment of heteroaromatic compound and its corresponding tetrahydro derivative

Answer 1

The orientational influence of dipolar solutes on the aromatic solvents, benzene and hexafluorobenzene, as reflected by nmr chemical shifts, has been used to determine the direction of the dipole moments of thiophene, furan, pyrrole, and N-methylpyrrole. The direction for pyrroles with nitrogen at the positive end was confirmed. Contrary to popular belief, the direction of the dipole moments of the chalcogen heterocycles was found not to be reversed from their saturated analogs but to maintain the direction, placing the heteroatom at the negative end.