Question

Question #4cbd1

Answer 1

I would expect the `"-SH"` group to be mildly activating.

Explanation:

The effect of substituents in electrophilic aromatic substitution is a combination of resonance and inductive effects.

The group is ortho-para directing because the lone pairs on the sulfur atom can be delocalized into the ring and stabilize positive charge at the ortho and para locations.

However, the effect is not large because of the mismatch in size between the large `"3p"` orbital on `"S"` and the smaller `"2p"` orbital on `"C"`.

This resonance donation of electrons to the ring should activate the ring to electrophilic aromatic substitution.

However, we must consider the possible inductive removal of electrons from the ring caused by electronegativity differences.

The electronegativity values are 2.55 for `"H"` and 2.58 for `"S"`.

The two atoms have almost the same electronegativity.

`ΔEN ≈ 0`

Hence, I predict that the resonance effect will predominate and the `"-SH"` group will be mildly activating.