Chapter 26, Problem 26.15P

Interpretation Introduction

Interpretation:

A mechanism for the reaction that occurs in Equation $\text{26-34}$ is to be proposed. It is to be determined whether the reaction will be as successful if the tert-butyl group were a linear butyl group instead.

Concept introduction:

To isolate the Poly (ether ether ketone) or PEEK, the tert-butyl group can be removed from aryl ring by adding excess of toluene in an acidic condition. In this reaction, the tert-butyl group is removed from the aryl ring of PEEK and attached to toluene. The overall reaction is trans tert-butylation, that is, the reaction is reverse of Friedel-Craft alkylation. The removal of tert-butyl takes place through electrophilic aromatic substitution, followed by electrophile elimination, where tert-butyl is eliminated as tertiary carbocation, which then undergoes electrophilic aromatic substitution with toluene. The trans alkylation is possible in this case because of the formation of more stable tertiary carbocation; the reaction would not be possible when the carbocation formed would be a primary one as it is less stable.