Question

1) What is the advantage of using pyridinium bromide perbromide as brominating agent?

2) (E)-Stilbene (500 mg) in acetic acid (10 mL) was treated with pyridinium bromide perbromide (1.2 gm) to yield meso-dibromostilbene (750 mg). Calculate percentage yield.

3) What product would you expect by the addition of bromine to cyclopentene? Draw the starting material, intermediate and product. Show the stereochemistry

Answer 1

1.

Elemental bromine is volatile and highly corrosive, causing severe burns upon contact with the skin and extremely irritating upon inhalation. Pyridinium bromide perbromide exists in rapid equilibirium with pyridinium hydrobromide and bromine and thus provides for the slow release of bromine into the reaction medium. An additional advantage of pyridinium bromide perbromide is that it is an easily weighed solid.

2.

3.