Question

What is the role of pyridinium tribromide in the bromination of trans-cinnamic acid?

A. Pyridinium tribromide generates Br₂ in situ.
B. Pyridinium tribromide serves as a catalyst.
C. Pyridinium tribromide is used as a limiting reactant in the bromination of transcinnamic acid.
D. Pyridinium tribromide is required for the final product to crash out as a solid during the aqueous work-up.
E. Pyridinium tribromide separates trans-cinnamic acid and the dibrominated product into two separate layers.

Answer 1

Pyridinium tribromide's role is to generate bromine (Br₂) in situ during the bromination of trans-cinnamic acid, which is answer A.

Step-by-step explanation:

The role of pyridinium tribromide in the bromination of trans-cinnamic acid is to generate Br₂ in situ. This means that pyridinium tribromide produces bromine within the reaction mixture, which then reacts with the trans-cinnamic acid to add bromine atoms to the compound.

Pyridinium tribromide is not a catalyst, nor is it a limiting reactant; it also does not have any role in causing the final product to crash out as a solid during aqueous work-up, nor does it separate layers between the trans-cinnamic acid and the dibrominated product. Therefore, the correct answer to this question is A: Pyridinium tribromide generates Br₂ in situ.