Match List I with List II.

List I:
(A) Chloroprene
(B) Neoprene
(C) Acrylonitrile
(D) Isoprene

Lis

Q: How do I know structure (i) is Isoprene and not just a random diene?

In skeletal structures, an unlabeled line extending from a carbon backbone represents a methyl ($\mathrm{CH_3}$) group. Since it's attached to the second carbon of a 1,3-butadiene chain, it is 2-methyl-1,3-butadiene, which is the IUPAC name for Isoprene.

Q: What is the difference between addition and condensation polymers?

Addition polymers (like Neoprene) are formed by the repeated addition of monomer molecules with double or triple bonds, without the loss of any small molecules. Condensation polymers involve the loss of small molecules like water during formation.

Q: Why does the double bond shift in Neoprene compared to Chloroprene?

During the addition polymerization of 1,3-dienes, the reaction typically proceeds via a 1,4-addition mechanism. The pi electrons rearrange, forming new single bonds to adjacent monomers and creating a new double bond in the center (between C2 and C3).

Q: Is Acrylonitrile used to make any common polymers?

Yes! Acrylonitrile is the monomer for Polyacrylonitrile (PAN), which is widely used to make synthetic fibers like Orlon, often used as a substitute for wool.

Q: How can I memorize these common names?

The best way is to associate them with their applications. Isoprene = Natural Rubber. Chloroprene = Synthetic Rubber (Neoprene). Acrylonitrile = Synthetic Wool (Orlon). Connecting the chemical name to a real-world object makes it stick!

Question

Match List I with List II.

\begin{array}{ll}
	extbf{List I} & 	extbf{List II} \
	ext{(A) Chloroprene} & 	ext{(i)} \
	ext{(B) Neoprene} & 	ext{(ii)} \
	ext{(C) Acrylonitrile} & 	ext{(iii)} \
	ext{(D) Isoprene} & 	ext{(iv) } \mathrm{CH_2=CH-CN}
\end{array}

Choose the correct answer from the options given below.

Options:

(A) A-(iii), B-(iv), C-(ii), D-(i)

(B) A-(ii), B-(iii), C-(iv), D-(i)

(C) A-(ii), B-(i), C-(iv), D-(iii)

(D) A-(iii), B-(i), C-(iv), D-(ii)

Sigma Percentile · Accepted Answer

### Decoding the Language of Polymers

Welcome to a classic journey through polymer chemistry! In this problem, we are tasked with bridging the gap between the common names of famous industrial molecules and their exact chemical structures. This isn't just about memorization; it's about recognizing the functional groups that give these materials their unique properties.

Let's break down the list systematically.

### Analyzing Chloroprene

We begin with **Chloroprene**. What exactly is it? Its formal IUPAC name is $2	ext{-chloro-}1,3	ext{-butadiene}$. This tells us we are dealing with a four-carbon chain containing two double bonds (a diene), with a chlorine atom attached to the second carbon.

When we scan the given structures, structure (ii) perfectly matches this description. You can clearly see the zig-zag butadiene backbone and the chlorine atom pointing upwards. Therefore, we can confidently say that **(A) matches with (ii)**.

### The Polymerization to Neoprene

Next up is **Neoprene**. Neoprene is a highly resilient synthetic rubber. But how is it made? It is simply the polymer formed from the chloroprene monomer we just identified.

During addition polymerization, the double bonds in the diene shift, allowing the molecules to link together into a continuous, long chain. Looking at our options, structure (iii) is the only one depicted as a polymer chain, indicated by the brackets and the subscript $n$. Notice how the repeating unit still retains that signature chlorine atom. Thus, **(B) matches with (iii)**.

### Spotting Acrylonitrile

Moving on to **Acrylonitrile**. This is a very straightforward molecule. It consists of a vinyl group ($\mathrm{CH_2=CH-}$) attached directly to a cyanide, or nitrile, group ($\mathrm{-CN}$).

Looking at our choices, structure (iv) is explicitly written out as exactly this formula: $\mathrm{CH_2=CH-CN}$. There are no complex skeletal structures to decode here! So, **(C) clearly matches with (iv)**.

### The Secret of Isoprene

Finally, we have **Isoprene**. This is a crucial molecule to remember because it is the fundamental building block (monomer) of natural rubber. Chemically, it is known as $2	ext{-methyl-}1,3	ext{-butadiene}$.

Notice how similar it is to chloroprene? The only difference is that the chlorine atom is replaced by a methyl group. By elimination, and by looking at structure (i), we see the familiar butadiene backbone with a single, unlabeled line pointing up. In skeletal structures, an unlabeled line represents a methyl ($\mathrm{CH_3}$) group. Therefore, **(D) matches with (i)**.

### Bringing It All Together

Let's compile our findings:
- $	ext{(A)} ightarrow 	ext{(ii)}$
- $	ext{(B)} ightarrow 	ext{(iii)}$
- $	ext{(C)} ightarrow 	ext{(iv)}$
- $	ext{(D)} ightarrow 	ext{(i)}$

Checking our given options, this sequence perfectly aligns with option (b).

**Pro Tip:** Always remember the subtle difference between isoprene and chloroprene. One makes natural rubber, the other makes synthetic neoprene. Just swapping a methyl group for a chlorine atom completely changes the physical properties of the resulting polymer. Keep practicing these structures, and you'll spot them instantly in your exams!

Select Answer:

Visualized Solution

$A na l y z in g t h e P o l y m er s an d M o n o m er s$

$S t r u c t u r e o f C h l or o p r e n e$

$M a t c hin g (A)$

$S t r u c t u r e o f N eo p r e n e$

$M a t c hin g (B)$

$S t r u c t u r e o f A cr y l o ni t r i l e$

$M a t c hin g (C)$

$S t r u c t u r e o f I so p r e n e$

$M a t c hin g (D)$

$F ina l C o n c l u s i o n$

$K ey T ak e a w a y s$

The Sigma Insight: Polymers

Decoding the Language of Polymers

Analyzing Chloroprene

The Polymerization to Neoprene

Spotting Acrylonitrile

The Secret of Isoprene

Bringing It All Together

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