1. Tardigrade
  2. Question
  3. Chemistry
  4. Arrange the following monomers in order of decreasing ability to undergo cationic polymerisation. I. CH2 = CH - C6H4(NO2) II.CH2 = CH - C6H4(CH3) III. CH2 = CH - C6H4(OCH3)

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Q. Arrange the following monomers in order of decreasing ability to undergo cationic polymerisation.
I. $CH_2 = CH - C_6H_4(NO_2)$
II.$CH_2 = CH - C_6H_4(CH_3)$
III. $CH_2 = CH - C_6H_4(OCH_3$)

AIIMSAIIMS 2017Polymers

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
$\underset{(III)}{CH_2 = CH - C_6H_4(OCH_3)} > \underset{(II)}{CH_2 = CH - C_6H_4(CH_3)} > \underset{(I)}{CH_2 = CH -C_6H_4(NO_2)}$