Which of the following compounds will undergo polymerization reaction?

Step 1: Analyze the question We need the compound that can join with many identical molecules to form a long chain (a polymer).

Step 2: The concept Addition polymerization needs a monomer with a double bond (unsaturated), usually an alkene. The double bond opens up, and the molecules link together:

n CH₂=CH₂ → –(CH₂–CH₂)ₙ– (polyethene)

Saturated compounds have only single bonds, so they have no site for this chain-building reaction.

Step 3: Check each option

• A. C₂H₄ is ethene, CH₂=CH₂. It has a C=C double bond, so it polymerizes to polyethene (polythene). ✔
• B. C₂H₅COOH is propanoic acid. It is saturated in its carbon chain, and the C=O in the carboxyl group does not undergo addition polymerization. ✘
• C. C₂H₆ is ethane, a saturated alkane. It is unreactive toward polymerization. ✘
• D. C₂H₅OH is ethanol, which is saturated. ✘

Step 4: Answer The correct option is A, C₂H₄ (ethene).

Exam tip: In polymerization questions, look for the double bond. Alkenes such as ethene, propene, and chloroethene (vinyl chloride) are the typical monomers, and the usual products are polythene, polypropene, and PVC. A quick formula check also helps: CₙH₂ₙ is an alkene, while CₙH₂ₙ₊₂ is an alkane and will not polymerize.