Diane O'File treated 1,3-cyclohexadiene with Br2 and obtained two products (ignoring stereoisomers). Her lab partner treated 1,3-cyclohexadiene

Question:

Diane O'File treated 1,3-cyclohexadiene with Br2 and obtained two products (ignoring stereoisomers). Her lab partner treated 1,3-cyclohexadiene with HBr and was surprised to find that he obtained only one product (ignoring stereoisomers). Account for these results.