There are three dibromobenzenes (o-, m-, and p-). Suppose we have samples of each in separate bottles, but we don't know which is which. Let us call them A, B, and C. On nitration, compound A (mp 87°C) gives only one nitrodibromobenzene. What is the structure of A? B and C are both liquids. On nitration, B gives two nitrodibromobenzenes, and C gives three nitrodibromobenzenes (of course, not in equal amounts). What are the structures of B and C? Of their mononitration products? (This method, known as Korner's method, was used years ago to assign structures to isomeric benzene derivatives.)