List of top Chemistry Questions on preparation of haloarenes asked in BITSAT

The following reaction is known as: 
 \[ \text{C}_6 \text{H}_5 \text{COOH} + \text{CO}_2 \xrightarrow{120-140^\circ C, 1.5 \, \text{atm}} \text{C}_6 \text{H}_4 \text{COONa} \xrightarrow{\text{NaOH}} \text{C}_6 \text{H}_5 \text{COOH} \]

In Gattermann reaction, a diazonium group is replaced by using $\underline{Y} \underline{X}$and $\underline{Y}$ are