`C_(6)H_(4)(CH_(3))_(2)` is present in how many isomeric forms (benzene derivatives).

C_(7)H_(9)N has how many isomeric forms that contain a benzene ring?

Isopentane, (CH_(3))_(2)CHCH_(2)CH_(3) can form four isomeric monochloro derivatives. How many of these are optically active?

C_(6)H_(5)-O-CH_(2)CH_(3)overset(HI)rarr which of the following is not formed in this reaction ?