 An unprotected alcohol group of either the sugar or the dye is reacted with an n-carbon, terminal dibromoalkane in a solution of potassium hydroxide and 18-crown-6 ether, using non-anhydrous tetrahydrofuran as the solvent.The potassium hydroxide is used to produce an alkoxide ion from the alcohol while the 18-crown-6 ether acts as a phase-transfer agent.The reaction proceeds through a classic SN-2 nucleophilic substitution.