Question #572ed

1 Answer
Mar 28, 2015

What role does NaOH play in the synthesis of nerolin (β-methoxynaphthalene)?

The NaOH converts the β-naphthol into a much stronger nucleophile.

The synthesis of nerolin is an example of the Williamson ether synthesis, which is an #"S"_"N"2# displacement reaction.

Phenols are neutral molecules.

This makes them poor nucleophiles. They will not react with methyl iodide.

ArOH + CH₃-I #cancel(→)# ArO-CH₃ + HI

But phenols are also weak acids.

The strong base NaOH reacts with β-naphthol and converts it to the β-naphthoxide:

ArOH + OH⁻ → ArO⁻ + H₂O

Since the naphthoxide ion now has a negative charge, it is a much stronger nucleophile than the original naphthol.

It now reacts with the ethyl iodide in an #"S"_"N"2# reaction to form β-methoxynaphthalene.

ArO⁻ + CH₃-I → ArO-CH₃ + I⁻