Synthesis of Nylon
A solution of sebacoyl chloride in hexane is gently poured on top of a basic aqueous solution of hexamethylenediamine in a crystallization dish. A film of nylon forms at the interface. When the film is pulled out of the system with forceps, it forms into a thick, ropy strand that can be would around a stirring rod "spindle."
This demonstration can be used in any course when polymers are being discussed. In an organic chemistry class, it is probably most useful when discussing nucleophilic acyl substitution. This demo takes about ten minutes to perform.
Nylon is a generic name for several synthetic polyamides. In this demo 6-10 nylon is synthesized. This means that the carbon chains between the amide bonds alternate between six and ten carbons in length. The condensation reaction is: H2N(CH2)6NH2 + ClCO(CH2)8COCl --> -[-NH(CH2)6NHCO(CH2)8CO-]- +2HCl. This is an example of nucleophilic acyl substitution with the amine nitrogen acting as a nucleophile to displace chloride ion from the carbonyl carbon. The base is present to neutralize the acid byproduct so that it does not protonate the amine, thus effectively deactivating it. Bassam Shakashisri. Chemical Demonstrations, v.1, pp. 213-215. The University of Wisconsin Press; Madison, WI. 1983.
- 50 mL 0.5M heamethylenediamine (1,6-diaminohexane) in 0.5M NaOH
- 50 mL 0.2M sebacoyl chloride in hexane
- 100 x 50 mm crystallization dish
- nitrile gloves
- 2 small glass stirring rods
- paper towels
- Pour the hexamethylene diamine solution into the crystallization dish.
- Slowly add the sebacoyl chloride solution, creating as little turbulence as possible. It helps to pour down the surface of a stirring rod. Two immiscible layers form.
- Reach into the center of the dish with the forceps and grab the film that has formed at the interface.
- Pull the film up and loop it around a stirring rod.
- Spin the stirring rod, pulling up a continuous strand of nylon.
- Both solutions are caustic and irritating to the skin, eyes, and respiratory system. Exercise caution when preparing and using these solutions. Use nitrile gloves and goggles. Prepare and perform this demo in a well-ventilated space.
- Hexane is extremely flammable. Keep a fire-extinguisher near at hand.
Instructions for preparing these solutions can be found in volume 1 of Chemical Demonstrations, by Bassam Shakashiri.