The reaction of 1,6-hexanediamine with hexanedioic acid chloride to form nylon 6-6 is a condensation polymerization. What is the small molecule that is split off in each step of the reaction?

My best guess is HCl.

In the reaction of 1,6-hexanediamine with hexanedioic acid chloride to form nylon 6-6, a condensation polymerization reaction occurs. In each step of this reaction, a small molecule called hydrogen chloride (HCl) is split off.

Here is a step-by-step breakdown of the reaction:

1. The reaction begins with 1,6-hexanediamine, which has two amine groups (-NH2) on each end of a 6-carbon chain:

H2N-(CH2)6-NH2

2. Hexanedioic acid chloride, also known as adipoyl chloride, has two acid chloride groups (-COCl) on each end of a 6-carbon chain:

ClCO-(CH2)4-COCl

3. When these two reactants are combined, an amide bond (–CONH–) forms between the amine group of 1,6-hexanediamine and the acid chloride group of hexanedioic acid chloride:

H2N-(CH2)6-NH-CO-(CH2)4-COCl + HCl

This reaction eliminates a molecule of hydrogen chloride (HCl) as a byproduct.

4. The formation of this amide bond repeats, with more 1,6-hexanediamine and hexanedioic acid chloride units, to build the nylon 6-6 polymer chain.

By continuously removing hydrogen chloride (HCl) as a byproduct, the polymerization process continues until the desired chain length is achieved.

To determine the small molecule that is split off in each step of the reaction, we need to understand the process of condensation polymerization and the specific reaction between 1,6-hexanediamine and hexanedioic acid chloride to form nylon 6-6.

Condensation polymerization involves the repeated condensation reactions between monomers, resulting in the formation of a polymer while releasing a small molecule as a byproduct. In this case, 1,6-hexanediamine and hexanedioic acid chloride react to form nylon 6-6 through a condensation reaction.

The reaction between 1,6-hexanediamine and hexanedioic acid chloride (also known as adipoyl chloride) can be represented as:

NH2(CH2)6NH2 + ClC(O)C(O)Cl → (NH(CH2)6NHCOC(O))n + 2HCl

Here, 1,6-hexanediamine (NH2(CH2)6NH2) reacts with hexanedioic acid chloride (ClC(O)C(O)Cl) to form a nylon polymer, represented as (NH(CH2)6NHCO) with repeating units, usually denoted as "n" to indicate the polymer chain length. Two molecules of hydrochloric acid (HCl) are released as byproducts.

Hence, the small molecule split off in each step of the reaction is hydrochloric acid (HCl).