Consider the given reaction sequence and identify the final major product 'X'.

Step-by-step solution

The given starting material is p-toluenediazonium chloride. In step (i), the reaction with Cu ₂ Cl ₂ / HCl is a Sandmeyer reaction. The diazonium group ( - N ₂^+ Cl ^- ) is replaced by a chlorine atom to form p-chlorotoluene. In step (ii), p-chlorotoluene reacts with magnesium ( Mg ) in the presence of dry ether to form a Grignard reagent, p-tolylmagnesium chloride. In step (iii), the Grignard reagent undergoes an acid-base reaction with heavy water ( D ₂ O ). The nucleophilic carbon attached to magnesium abstracts