Question

Choose the answer that best explains why α–pyrone reacts with br2 to yield a substitution product (like benzene does), rather than an addition product to one of its c═c bonds.

Answer 1

As can be seen in the attached image, α-pyrone has a highly electrophilic carbon atom, since it is attached to two oxygen atoms that are electronegative and subtract electrical charge from the carbon, leaving it with a positive partial charge. By virtue of the above, the bromine atoms, which have an important electron density that makes them good nucleophiles, will be attracted to the aforementioned carbon due to their positive charge, thus favoring the substitution product to a greater extent than that of addition.