PROBLEM 12.43 - Organic Chemistry

Question

Question: Hydrogenation of alkene A with D2 in the presence of Pd-C affords a single product B. Keeping this result in mind, what compound is formed when A is treated with each reagent: 

(a) mCPBA; (b) Br₂ , H₂O followed by base? Explain these results.

Step-by-Step Solution

Answer

Answer

a.

Product of (a)

b.

trans adddition products

Meta-chloroperoxybenzoic acid (mCPBA)

The mCPBA acts as an oxidant and reacts with the $\mathrm{C}=\mathrm{C}$ bond in cycloalkenes, resulting in the formation of epoxide at the place of the double bond.

Reaction of bromine with cycloalkene

The double bond of C=C attacks the bromine molecule, resulting in the formation of a bromonium ion attached to the two carbon atoms of C=C. The positive charge is neutralized by the backside attack of the bromonium ion on the lesser substituted carbon of C=C.  

Products of the given reaction

a. The oxygen attacks from the upside of the ring, resulting in the formation of an up epoxide ring. The product is shown hereunder. 

Product of (a)

b. An anti-addition of Br and OH group takes place on the C=C. The OH group adds to the more substituted carbon of C=C. 

Product of (b).