What product forms when bromine water reacts with an alkene in this test?

• A. A dibromoalkane
• B. A monobrominated alkane
• C. A dibrominated benzene
• D. An alcohol

Answer: (A)

When bromine water meets an alkene, the double bond acts like a trap for bromine. Electrophilic bromine adds across the C=C, one bromine attaching to each carbon, so you get a vicinal dibromide. The bromine water loses its orange color because Br2 is consumed in forming this new C–Br–C–Br linkage. So the product is a dibrominated alkane. This isn’t a monobrominated alkane, a dibrominated aromatic ring, or an alcohol under these conditions.