The two monomers for the synthesis of nylon 6, 6 are
(a) HOOC(CH2)4COOH, H2N(CH2)4NH2
(b) HOOC(CH2)6

Q: Why is it called Nylon 6,6 and not just Nylon 12?

The comma separates the carbon count of the two distinct monomers. 'Nylon 12' would imply a homopolymer made from a single monomer containing 12 carbon atoms (like $\omega$-aminolauric acid). 'Nylon 6,6' explicitly tells us it's a copolymer made of a 6-carbon diamine and a 6-carbon diacid.

Q: What is the difference between Nylon 6 and Nylon 6,6?

Nylon 6 is a homopolymer made from a single monomer called caprolactam, which has 6 carbon atoms. Nylon 6,6 is a copolymer made from two different monomers (hexamethylenediamine and adipic acid), each having 6 carbon atoms.

Q: Why does adipic acid have only 4 $CH_2$ groups if it's a 6-carbon monomer?

You must count all the carbon atoms in the molecule, including the ones in the functional groups. Adipic acid has 4 carbons in the central $-(CH_2)_4-$ chain, plus 2 carbons in the two $-COOH$ groups at the ends, making a total of 6 carbons.

Q: Why is water eliminated in this reaction?

This is a classic nucleophilic acyl substitution reaction. The lone pair on the nitrogen of the amine attacks the carbonyl carbon of the acid. To restore the stable carbonyl double bond, a leaving group must be expelled. The $-OH$ from the acid and an $-H$ from the amine combine to leave as a stable water molecule ($H_2O$).

Q: Can we use any diamine and dicarboxylic acid to make Nylon?

Yes! By varying the chain lengths of the diamine and the diacid, you can create different types of Nylon (like Nylon 6,10 or Nylon 4,6), each with slightly different physical properties like melting point and flexibility.

Question

The two monomers for the synthesis of nylon 6, 6 are

Options:

(A) $	ext{HOOC(CH}_2	ext{)}_4	ext{COOH, H}_2	ext{N(CH}_2	ext{)}_4	ext{NH}_2$

(B) $	ext{HOOC(CH}_2	ext{)}_6	ext{COOH, H}_2	ext{N(CH}_2	ext{)}_4	ext{NH}_2$

(C) $	ext{HOOC(CH}_2	ext{)}_4	ext{COOH, H}_2	ext{N(CH}_2	ext{)}_6	ext{NH}_2$

(D) $	ext{HOOC(CH}_2	ext{)}_6	ext{COOH, H}_2	ext{N(CH}_2	ext{)}_6	ext{NH}_2$

Sigma Percentile · Accepted Answer

### The Secret Language of Polymers

Have you ever wondered why some polymers have numbers in their names? Take **Nylon 6,6** for example. Those numbers aren't just random serial codes; they are a secret chemical language that tells us exactly how the polymer was built.

In the world of polymer chemistry, Nylon belongs to a family called **polyamides**. Just like proteins in our bodies are held together by peptide bonds, polyamides are held together by amide linkages. To create an amide linkage, we need two specific functional groups to react: an amine group ($-NH_2$) and a carboxylic acid group ($-COOH$).

### Decoding the "6,6"

Because Nylon 6,6 is a copolymer, it requires two different building blocks (monomers) to form its long chain.

1.  **The Diamine:** We need a molecule with an amine group at both ends. The first "6" in Nylon 6,6 tells us that this diamine must contain exactly 6 carbon atoms. A straight chain of 6 methylene ($-CH_2-$) groups capped with amines gives us **hexamethylenediamine**: $H_2N-(CH_2)_6-NH_2$.
2.  **The Dicarboxylic Acid:** We need a molecule with a carboxylic acid group at both ends. The second "6" tells us that this acid must also contain exactly 6 carbon atoms. Since the two $-COOH$ groups already account for 2 carbon atoms, the middle of the chain must have 4 carbon atoms. This gives us **adipic acid**: $HOOC-(CH_2)_4-COOH$.

### The Condensation Magic

When hexamethylenediamine and adipic acid are mixed and heated, a beautiful chemical dance occurs. The $-OH$ from the carboxylic acid and an $-H$ from the amine group break off and combine to form a water molecule ($H_2O$).

Because a small molecule like water is eliminated during the reaction, this is called a **condensation polymerization**. The remaining fragments bond together, forming a strong $-NH-CO-$ amide linkage. This process repeats thousands of times, creating the incredibly strong and durable fibers of Nylon 6,6 that we use in everything from clothing to parachutes.

By simply counting the carbons in the options provided, we can easily spot the correct pair: Adipic acid ($HOOC(CH_2)_4COOH$) and Hexamethylenediamine ($H_2N(CH_2)_6NH_2$).

Animated Solution for Chemistry - Organic Chemistry: The two monomers for the synthesis of nylon 6, 6 are

Select Answer:

Visualized Solution

$N y l o n 6, 6 N o m e n c l a t u r e$

$P o l y ami d e F or ma t i o n$

$T h e D iamin e M o n o m er$

$T h e D i c a r b o x y l i c A c i d M o n o m er$

$T h e C o n d e n s a t i o n R e a c t i o n$

$F ina l A n s w er$

The Sigma Insight: Polymers

The Secret Language of Polymers

Decoding the "6,6"

The Condensation Magic

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