Product X formed in the above reaction is:

 The alcohol is reacted with a mixture of sodium iodide and concentrated phosphoric acid, ${\mathrm{H}}_3{\mathrm{PO}}_4$, and the iodoalkane is distilled off. The 2-iodobutane formed in the previous reaction give Grignard reagent with magnesium metal in dry ether. The Grignard reagent formed reacts with ${\mathrm{D}}_2\mathrm{O}$ to give 2-deuterobutane.