Question

Which of the following combination of reagents can bring the shown transformation ?

• A. $C{H}_{3}ONa,Mg/\text{ether},C{O}_2,H_{2}O/H^{+}$
• B. $C{H}_{3}ONa,KCN/DMSO,H_{2}O/H_{2}S{O}_4,\text{heat}$
  
• C. $Mg/\text{ether,}C{O}_2,H_{2}O/H^{+},C{H}_{3}ONa$
• D. $NaOH,Mg/\text{ether,}C{O}_2,H_{2}O/H^{+},C{H}_{3}I$

Answer 1

The correct option is A $C{H}_{3}ONa,Mg/\text{ether},C{O}_2,H_{2}O/H^{+}$

The combination (A) $C{H}_{3}ONa,Mg/\text{ether,}C{O}_2,H_{2}O/H^{+}$ can bring the shown transformation.
Aliphatic bromine is replaced with methoxy group by reaction with sodium methoxide. It is nucleophilic substitution reaction. The aromatic bromine reacts with Mg/ether to form Grignard reagent (aryl magnesium bromide) which then attacks carbon dioxide molecule. This is followed by acid hydrolysis. The net result is the replacement of aromatic bromine with carboxylic group.