C2H5CL+KOH(spirt)--->C2H4 + KCL + H2O C2H4 + BR2------>C2H4BR2 C2H4BR2 + 2KOH(spirt)----->C2H2 + 2KBR + 2H2O C2H2 + H2O------->CH3-CHO (над стрелкой Hg)