Question

Is thiophene an aromatic?

Answer 1

Yes, thiophene is an aromatic compound.

According to Hückel's rule, a planar, conjugated, cyclic molecule is aromatic if it has `4n+2` π electrons. The value of `n` can be zero or any positive integer.

The most common aromatic molecule is benzene (`n =1`).

Pyrrole, furan, and thiophene are other aromatic compounds with `n =1`.

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The heteroatoms each contribute two electrons to the π system.

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However, the resonance stabilization in thiophene (122 kJ/mol) is less than that in benzene (152 kJ/mol), because `"S"` is more electronegative than `"C"`.

`"S"` is less "willing" to donate its electrons to the aromatic system.

But, because thiophene is aromatic, it does not have the properties of ordinary thioethers.