Organic Chemistry Nylon Synthesis Lab

Nylon is a group of synthetic organic compounds used in textiles and plastics. They can be classified as condensation polymers, more specifically polyamides. Condensation is a reaction in which two molecules are joined together along with the loss of a small molecule such as water. In this lab experiment, adipoyl chloride will be added to 1,6-hexanediamine to make nylon-6,6. The acid chloride and amine react and are joined in a condensation process with loss of the HCl molecule. The product contains a newly formed amide bond. The resulting product has both acid chloride and amine functional groups on the terminal ends that can react with molecules of 1,6-hexanediamine and adipoyl chloride, respectively. This process continues until all the reagents have reacted to form Nylon 6,6 polymer.

Nylon’s unique properties are a result of these strong amide bonds which are highly polar in nature. It is known for its high tensile strength, flexibility, heat and chemical resistance as well as its ability to be easily dyed.

Beaker A (Organic Phase): 8 mL cyclohexane, 0.4 mL adipoyl chloride.

Beaker B (Aqueous Phase): 8 mL 1,6-hexanediamine, 8 drops NaOH.

The organic solution was slowly poured into the aqueous solution, forming two layers. A thin nylon film formed at the interface. The film was grasped with a glass rod and continuously pulled, forming a fiber. The fiber was rinsed, dried, and weighed. An IR spectrum of the nylon sample was obtained.

The polymer formed via step-growth polymerization at the interface between the organic and aqueous layers. NaOH played a crucial role by neutralizing HCl:

HCl + NaOH → NaCl + H₂O

Without NaOH, HCl would protonate the amine and stop polymerization. The mass of nylon obtained (1.2628 g) indicates successful polymer formation. Yield may be reduced due to hydrolysis of adipoyl chloride by water, incomplete drying, and diffusion limitations at the interface.

The experiment successfully demonstrates:

• Nucleophilic acyl substitution
• Condensation polymerization
• Interfacial reaction kinetics
• Structure–property relationships

Nylon’s mechanical strength results from strong hydrogen bonding between chains.

A condensation polymer is a polymer formed through a step-growth reaction between monomers that contain two or more functional groups, where each bond formation is accompanied by the elimination of a small molecule such as water (H₂O) or hydrogen chloride (HCl). In condensation polymerization, the monomers join together through repeated condensation reactions, forming long polymer chains while releasing small by-products. In the case of nylon-6,6, the polymer forms when a diamine reacts with a diacid chloride and eliminates HCl during each amide bond formation.

I. High Tensile Strength — Nylon has strong intermolecular hydrogen bonding between amide groups (–CONH–) along the polymer chain. These hydrogen bonds hold adjacent chains tightly together, increasing mechanical strength and allowing nylon to withstand stretching without breaking.

II. Heat Resistance — The strong hydrogen bonding and partial crystallinity of nylon increase its melting point. The ordered arrangement of polymer chains makes it more thermally stable than many other polymers.

III. Chemical Resistance — The long hydrocarbon segments in nylon’s backbone provide hydrophobic character, making it resistant to many chemicals and solvents. The stable amide linkage also contributes to its durability.

IV. Ability to Be Dyed Easily — Nylon contains polar amide groups that can form hydrogen bonds and dipole interactions with dye molecules, allowing dyes to bind effectively for textile applications.

N–H stretch at 3300.10 cm⁻¹; C–H stretches at 2932.72 and 2859.59 cm⁻¹; C=O stretch at 1633.18 cm⁻¹; N–H bend at 1536.51 cm⁻¹; C–N stretch in the 1274.95–1188.58 cm⁻¹ region.