Question

What is the correct $IUPAC$ name of the compound shown below?

• A. 5 ,6 -dibromo-6-chloro-1, 3-cyclohexadiene
• B. 5, 6-dibromo-5-chloro-1, 3-cyclohexadiene
• C. 1,2-dibromo-1-chloro-3, 5-cyclohexadiene
• D. 2, 3-dibromo-2-chloro-1, 4-cyclohexadiene

Answer 1

Answer: (B)

When numbering diene preference is given to double bonds irrespective of positions of other alkyl and halide locants. Hence, correct numbering is

Here, halogen locants are at 5, 5, 6 positions, had the compound been numbered clockwise, halogen locants would have come at 5 ,6 ,6 which is wrong