Chapter 21, Problem 21.11P

Interpretation Introduction

Interpretation:

Major product of the sequence of reactions shown is to be determined.

Concept introduction:

The OH group in an alcohol is a poor leaving group as the hydroxide ion is a strong base. For substitution reactions, therefore, it is necessary to convert it to a good leaving group. One way to do this is to sulfonate the alcohol using a reagent such as tosyl chloride. This results in the replacement of the hydrogen in the alcoholic OH by the tosyl group. The bulky tosylate is an excellent leaving group. Further, as the reaction does not occur at the carbon atom, the configuration at the carbon is preserved if it is an asymmetric carbon. The tosylate can then be treated with a bulky, non-nucleophilic base to induce an E2 elimination. E2 elimintation involves elimination of the leaving group and a proton anticoplanar to it. Only the E isomer of the corresponding alkene is formed as a result.