Deduce the structures of A and B and choose the most appropriate option for the final major product B:
Deduce the structures of A and B and choose the most appropriate option for the final major product B:
The correct option is A The final product is an alkyne with 9 carbons
Initially, there is a chance that one might be confused between Bromination on the ring (electrophilic aromatic substitution) versus the electrophilic addition across the double bond (outside the benzene ring). The activation energy for electrophilic aromatic bromination is high even with a Lewis acid catalyst, which in this case is completely absent. So the electrophilic addition across the exocyclic double bond ensues. 2 Equivalents of NaNH3 gives us the terminal alkyne. The third equivalent deprotonates the acidic hydrogen of the terminal alkyne to yield an alkynyl carban ion nucleophile – which then attacks the methyl carbon CH3I to give the following B.
Initially, there is a chance that one might be confused between Bromination on the ring (electrophilic aromatic substitution) versus the electrophilic addition across the double bond (outside the benzene ring). The activation energy for electrophilic aromatic bromination is high even with a Lewis acid catalyst, which in this case is completely absent. So the electrophilic addition across the exocyclic double bond ensues. 2 Equivalents of NaNH3 gives us the terminal alkyne. The third equivalent deprotonates the acidic hydrogen of the terminal alkyne to yield an alkynyl carban ion nucleophile – which then attacks the methyl carbon CH3I to give the following B.
