It is not always easy to predict the position of attack on multiply substituted benzene. If the benzene ring bears different ortho//para directing group at the `1` and `4` positions, the position of further substitution is not immediately clear. Sometimes steric effects determine the outcome. In other cases, electronic factors determine the outcome, and further reaction will be at the position activated by the more strongly activating group.
Some substituens are so strongly activating that no catalyst is needed, and it is often diffcult to stop substitution after mono substituion. Mild condition are needed to restrict the reaction to mono-substitution.
It is possible to reduce the activity such groups by side chain reaction so that the reaction can be stopped use can sometimes be made of removable blocking groups on the ring.
Which of the following side reaction//s can be used to reduce the activity of strongly activating groups like `-OH` ?
A. benzcylation
B. acetylation
C. both of the above
D. none of the above
