# Isoptope effect on electrophilic aromatic substitution

Sulphonation will be the most effected electrophilic aromatic substitution reaction when benzene is replaced by hexadeutrobenzene.

I am not able to figure out how. All EAS reactions proceed by formation of an arenium ion and then the loss of an $$H^+$$ ion to regain aromaticity so all of them should be equally effected ( textbook does not mention how they are effected). I feel the only effect should be due to difference in bond enthalpies of $$C-D$$ bond and $$C-H$$ bond.

I came across this reaction mechanism from chemlibretexts: The hydrogen released is taken up by the $$-SO_3H^-$$

Can someone explain how and in what ways the replacement of hydrogen by deuterium effects the reaction ?

• Noting edits is not necessary. Anyone can see the edit history. – A.K. Apr 4 at 15:43