Identify the compound that will react with Hinsberg's reagent to give a solid which dissolves in alkali.

$1^0$ Amines react with Hinsberg's reagent $\left({\mathrm{C}}_6{\mathrm{H}}_5{\mathrm{SO}}_2\mathrm{Cl}\right)$ to form sulphonamides with an acidic Hydrogen.

Hence, these are soluble in alkali.

Soluble in alkali due to the presence of acidic hydrogen.