CHAPTER 9: Question 5

 

Simple Answers

The most stable conformation of A has the two phenyl groups antiperiplanar to one another as shown in the diagram below. This places the hydrogen atom, but not the deuterium atom in the correct location for a pyrolytic elimination. The elimination reaction is stereoselective, and since the two phenyl groups are anti to one another in the conformation of the starting material undergoing reaction, they remain anti to one another in the product, giving the trans or (E)-isomer of the alkene.

 The diastereomer of A would give the (E)-isomer of 1,2-diphenylethene which contains no deuterium.

 The enatiomer of A would give exactly the same product (B) as obtained from A.

 The reactions are stereoselective, but not stereospecific.
 

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