Question

(a) what product or products would you expect to obtain by the addition of bromine to cis-cinnamic acid, assuming that it reacts by the same mechanism as the trans cinnamic acid

Answer 1

If the totaling of bromine to cis-cinnamic acid uses the same mechanism or device as the addition to trans-cinnamic acid, addition of bromine only transpires on the top (syn) and not the bottommost face (anti). Therefore, bromine added to cis-cinnamic only adds to the same face (syn addition) as a result producing only threo dibromides.