Question

Fenfluramine and phentermine are two components of fen–phen, an appetite suppressant withdrawn from the market in 1997 after it was shown to damage the heart valves in some patients. What products are formed when fenfluramine and phentermine are each treated with acetic acid ${\mathbf{\text{CH}}}_{\mathbf{3}}{\mathbf{\text{CO}}}_{\mathbf{2}}\mathbf{\text{H}}$?

Short answer

Product of the reaction of fenfluramine with acetic acid

Product of the reaction of phentermine with acetic acid

Step-by-step solution

Proton transfer

The base donates one of its lone pairs of electrons to an acidic hydrogen atom in the acid and abstracts it. The hydrogen atom is thus transferred from the acid to the base.

Acidic hydrogen

The more acidic hydrogen atom is readily dissociated from the acid.

Reaction with acetic acid  of the given compounds

A more acidic proton is transferred to the base in each reaction.

In fenfluramine, the nitrogen atom is the donor atom and donates its lone pair of electrons to the acidic hydrogen atom of the acetic acid.

The reaction of fenfluramine with acetic acid

In phentermine, the nitrogen atom donates its lone pairs to the acetic acid.

The reaction of phentermine with acetic acid