What is 'C' in the given sequence of reactions?
In this reaction sequence, an aromatic compound undergoes a reaction with NaNO2/HCl, followed by hydrolysis with H2O/H3PO4, leading to the formation of a carboxyl group (COOH) as product 'C'.
The following graph indicates the system containing 1 mole of gas involving various steps. When it moves from Z to X, the type of undergoing process is: