Arrange the following monomers in order of decreasing ability to undergo cationic polymerisation. I. CH ₂= CH - C ₆ H ₄ ( NO ₂ ) II. CH ₂= CH - C ₆ H ₄ ( CH ₃ ) III. CH ₂= CH - C ₆ H ₄ ( OCH ₃ )

Step-by-step solution

Electron releasing groups such as - CH ₃,- OCH ₃ activate the monomer towards cationic polymerisation because these groups provide stability to the carbocation formed. On the other hand, - NO ₂ is a electron withdrawing group. So, it reduces the stability of carbocation formed. Thus, the correct order is