I made nylon in a lab with these procedures -

1) Collect 30mL of sebacoyl Chloride dissolved in hexane

2) collect 30mL of 1,6-hexanediamine dissolved in water .

3) Transfer the beaker containing sebacoyl Chloride in hexane and carefully pour the solution down the side of the beaker containing 1,6-hexanediamine in water , such that the hexane layer floats on TOP of the water layer , without mixing the layers.,

I got these procedures from the Internet .

Now , I got a few doubts and questions ..

  1. In the past , dichloromethane was used as the Solvent for the sebacoyl Chloride reagent. However dichloromethane is not environmentally friendly solvent and hexane was chosen to replace it in the experiment ...

a) how does switching it to hexane change the experimental procedures ?

b) What physical and chemical properties of the Solent must be considered when switching ?

c) why is hexane a good alternative in this experiment ?

Thanks in advance !


Nylon reaction:

$\ce{nH2N(CH2)6NH2 + nClOC(CH2)8COCl → H2N[(CH2)6NHCO(CH2)8]_{n}COCl + nHCl}$

Looking at the reagents, 1,6-hexanediamine is dissolved in water as it can form hydrogen bonds with the water molecules. Meanwhile the sebacoyl chloride is non-polar and thus dissolves best in non-polar solvents. The two solvents (polar and non-polar) cannot dissolve each other, just like oil and water.

The hexane is poured so it floats on top to minimize mixing -- the reaction only happens at the boundary between layers. Then we pull the thread causing more of the reagents to mix and react at the boundary. If we poured the hexane solution in quickly, we'd end up with a large lump of nylon instead of a thread.

To help with your other questions, some questions...

  1. I've given some details about the solvents above. What kind of solvents would you choose to replace the hexane and water with?
  2. Looking at the densities of hexane (0.659 g / mL) and water (1 g / mL), and looking at the procedure, why was the hexane poured? Why not pour the water onto the hexane?
  3. Following on, do some research into the density of dichloromethane. That will give you your answer to (a)
  4. You've mentioned "not enviromentally friendly" for dichloromethane. Are there any other issues? A good starting point are the CLEAPSS student safety sheets.

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