In the common naming system, the prefix sym- is used for haloarenes with how many halogen atoms?
Answer & explanation
Correct answer: option 3
The prefix sym- is used for trihaloarenes with same halogen atom at alternate positions in the benzene ring (1, 3, 5). The prefixes o-, m- and p- are used for dihaloarenes depending on the relative positions of the two identical halogen atoms on the aromatic ring.