How does benzene typically respond to bromine water in a simple test for unsaturation?

How does benzene typically respond to bromine water in a simple test for unsaturation?

• A. No reaction under ordinary conditions
• B. Immediate decolorization
• C. Formation of a precipitate
• D. Burning with flame

Answer: (A)

Bromine water tests for unsaturation by adding across carbon–carbon double bonds; this addition breaks the Br–Br bond and bleaches the solution. Benzene, though technically unsaturated, has a highly stabilized aromatic ring with electrons delocalized over the ring. This stability makes addition of bromine to benzene very unfavorable, so under ordinary conditions the bromine water does not react and the solution stays orange. Only with strong catalysts or drastic conditions that cause substitution on the ring would bromine be incorporated, but that isn’t the simple test for unsaturation. That’s why no reaction is the best description.

Bromine water tests for unsaturation by adding across carbon–carbon double bonds; this addition breaks the Br–Br bond and bleaches the solution. Benzene, though technically unsaturated, has a highly stabilized aromatic ring with electrons delocalized over the ring. This stability makes addition of bromine to benzene very unfavorable, so under ordinary conditions the bromine water does not react and the solution stays orange. Only with strong catalysts or drastic conditions that cause substitution on the ring would bromine be incorporated, but that isn’t the simple test for unsaturation. That’s why no reaction is the best description.