What does the designation '6,6' mean in the name nylon-6,6 ?

Explanation

To understand the designation '6,6' in the name nylon-6,6, we can break down the components involved in its formation:

### Step-by-Step Solution:

1. **Identify the Components**: Nylon-6,6 is synthesized from two specific monomers: adipic acid and hexamethylenediamine.

2. **Structure of Adipic Acid**: Adipic acid has the chemical formula C6H10O4. It contains a total of 6 carbon atoms (C) in its structure, which can be represented as:
- HOOC-(CH2)4-COOH
- This shows that adipic acid has two carboxylic acid (-COOH) groups and a chain of 4 methylene (-CH2-) groups.

3. **Structure of Hexamethylenediamine**: Hexamethylenediamine has the formula C6H16N2. It consists of 6 carbon atoms as well, structured as:
- NH2-(CH2)6-NH2
- This indicates that it has two amine (-NH2) groups and a chain of 6 methylene (-CH2-) groups.

4. **Formation of Nylon-6,6**: When adipic acid reacts with hexamethylenediamine, a condensation polymerization occurs, resulting in the formation of nylon-6,6. During this reaction, water is released as a byproduct.

5. **Understanding the Designation '6,6'**: The designation '6,6' in nylon-6,6 refers to the number of carbon atoms in each of the two monomers:
- The first '6' comes from the 6 carbon atoms in adipic acid.
- The second '6' comes from the 6 carbon atoms in hexamethylenediamine.

### Conclusion:
Thus, the designation '6,6' signifies that both the monomers used in the synthesis of nylon-6,6 contain 6 carbon atoms each.

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