Question

25) Treatment of cyclopentene with peroxybenzoic acid A) results in oxidative cleavage of the ring to produce an acyclic compound B) yields a meso epoxide C) yields an equimolar mixture of enantiomeric epoxides D) gives the same product as treatment of cyclopentene with OsO4 E) none of the above 26) Provide a detailed, step-by-step mechanism for the reaction shown below. но Br2 + HBr Br 27) Provide a detailed, step-by-step mechanism for the reaction shown below. 28) Provide the reagents necessary to complete the following transformation. The synthesis may involve more than one step. . O OH 29) Provide the reagents necessary to complete the following transformation. The synthesis may involve more than one step. Br OH + enantiomer **OH 30) Provide the reagents necessary to convert 3-methyl-2-butanol to 2-methyl-2-butanol. The synthesis may involve more than one step. 31) Both (E)- and (Z)-hex-3-ene are subjected to a hydroboration-oxidation sequence. How are the products from these two reactions related to each other? A) The (E)- and (Z)-isomers generate the same products but in differing amounts. B) The (E)- and (Z)-isomers generate the same products in exactly the same amounts. C) The products of the two isomers are related as constitutional isomers. D) The products of the two isomers are related as diastereomers. E) The products of the two isomers are not structurally related. IV

Answer 1

(25) • A chiral molecule is the one which contains a chiral center. They are optically active in nature and give optical isomers. Enantiomers are the optical isomers which are non- superimposable on their mirror images and contain opposite R and S descriptor on chiral center. A Meso compound contains a chiral center but optically inactive in nature due to presence of plane of symmetry in the molecule. A plane divides the molecule into two equal halves. Consider the given reaction and draw the product as shown below: Peroxybenzoic acid cyclopentene Epoxide In the above reaction, alkene reacts with peroxyacids and results in the formation of epoxide. The epoxide can be formed above as well as below the plane but as the structure is symmetrical so it will generate a meso compound due to presence of plane of symmetry in the structure as shown below: Meso compound (R) Same compound Plane of symmetry Hence the correct answer is option (B), i.e. the given reaction results in the formation of a meso epoxide.

Answer 2

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