Question

Neoprene is the polymer of a monomer X. IUPAC name of X is

• A. 1,3-Butadiene
• B. 2-Methyl-1,3-butadiene
• C. 2-Iodo-1,3-butadiene
• D. 2-Chloro-1,3-butadiene

Hint:

Memorize the monomers of the most important industrial polymers: - Polyethylene \(\rightarrow\) Ethene - PVC \(\rightarrow\) Vinyl chloride (Chloroethene) - Teflon \(\rightarrow\) Tetrafluoroethene - Natural Rubber \(\rightarrow\) Isoprene (2-Methyl-1,3-butadiene) - Neoprene \(\rightarrow\) Chloroprene (2-Chloro-1,3-butadiene) - Buna-S \(\rightarrow\) 1,3-Butadiene + Styrene

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
This question tests the knowledge of common addition polymers and their corresponding monomers. Neoprene is a synthetic rubber known for its good chemical stability and resistance to oil and heat.
Step 2: Identifying the Monomer of Neoprene:
Neoprene is the trade name for the polymer polychloroprene. It is formed by the free-radical polymerization of its monomer unit, chloroprene.
The structure of chloroprene is:
\[ \text{CH}_2=\underset{\text{Cl}}{\underset{|}{C}}-\text{CH}=\text{CH}_2 \] The polymerization reaction is: \[ n \left( \text{CH}_2=\underset{\text{Cl}}{\underset{|}{C}}-\text{CH}=\text{CH}_2 \right) \xrightarrow{\text{Polymerization}} \left[ -\text{CH}_2-\underset{\text{Cl}}{\underset{|}{C}}=\text{CH}-\text{CH}_2- \right]_n \] Step 3: Determining the IUPAC Name of the Monomer (X):
The monomer is chloroprene, with the structure \( \text{CH}_2=\text{C(Cl)}-\text{CH}=\text{CH}_2 \).

- The parent chain is a four-carbon chain containing two double bonds: a butadiene.

- The double bonds start at carbon 1 and carbon 3.

- There is a chlorine substituent at carbon 2.

- Therefore, the IUPAC name is 2-Chloro-1,3-butadiene.
Step 4: Analyzing Other Options:
- (A) 1,3-Butadiene is the monomer for Buna rubbers (e.g., Buna-S, Buna-N).
- (B) 2-Methyl-1,3-butadiene is the monomer for natural rubber. Its common name is isoprene.
- (C) 2-Iodo-1,3-butadiene is not a common monomer for a well-known polymer.
Final Answer:
The IUPAC name of the monomer X for neoprene is 2-Chloro-1,3-butadiene. Therefore, option (D) is correct.