Question

What is the purpose of the NaOH used in the reaction to make nylon from a diacyl chloride?

Why do the methylene chloride and hexane solutions form two layers? (Are hexane and methylene chloride immiscible? Try it!)

Why can’t you calculate the yield of nylon in moles (the usual unit used for % yield)?

For industrial nylon manufacturing, would you use the di-acid or the di-acyl chloride? Why?

Answer 1

1) Purpose of the NaOH in the reaction to make nylon from a diacyl chloride:

As the reaction proceeds, HCl is generated from the coupling of the amino groups to the acyl chloride molecules.

H₂N-(CH2)₆-NH₂ +   ClOC-CH₂-CH₂- COCl   -----------> H₂N-(CH2)₆-NH-CO-CH₂-CH₂- COCl   + HCl

As the HCl concentration rises, the unreacted amine will act as a base and deprotonate the HCl that is formed. The resulting ammonium salt is no longer nucleophilic and will not participate in the acylation reaction.

Hence, to prevent this, NaOH solution is added to quench the acid that forms, keeping the amine in a form that will be nucleophilic.

2) Hexane and methylene chloride are miscible. They do not from 2 layers.

Like dissolves like.   Since both are organic compounds, freely miscible with each other.