Diastereomers, alkyl halides elimination

Problem 8.18 Given that an E2 reaction proceeds with anti periplanar stereochemistry, draw the products of each elimination. The alkyl halides in (a) and (b) are diastereomers of each other. How are the products of these two reactions related ... 

Alkyl sulfonates offer a very real advantage over alkyl halides in reactions where stereochemistry is important this advantage lies, not in the reactions of alkyl sulfonates, but in their preparation. Whether we use an alkyl halide or sulfonate, and whether we let it undergo substitution or elimination, our starting point for the study is almost certainly the alcohol. The sulfonate must be prepared from 4he alcohol the halide nearly always will be. It is at the alcohol stage that any resolution will be carried out, or any diastereomers separated the alcohol is then converted into the halide or sulfonate, the reaction we are studying is carried out, and the products are examined. 

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