Question

Problem 7.28 Propose a mechanism for the following reaction DCI Draw all missing reactants and/or products in the appropriate boxes by placing atoms on the canvas and connecting them with bonds. Add charges wher should start on the electron(s) of an atom or a bond and should end on an atom, bond, or location where a new bond should be created. Use water to rep isotopic form of hydrogen, right-click the atom and choose Atom Properties (Mac users: Use an equivalent for right-clicking.) Then, enter the symbol of

Answer 1

DCl, deuterium chloride is a strong acid.
In the presence of a strong acid, benzene can be protonated to produce a resonance stabilized intermediate.

The water molecule can then grab the hydrogen atom to reform the aromatic benzene that is now substituted with the deuterium to form and leave as a hydronium ion H₃O⁺. The process repeated similarly 6 tikes to form the completely deuterated benzene. It thus forms 6 molecules of H₃O^+.

The key point here is that deuteration of benzene only takes place because aromaticity is regained.

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