Chapter 25q: Chapter Quiz

Exercise \(\PageIndex{1}\)

Which molecule in each of the following pairs of amines is more basic? Explain why.

Answer

Ethanamine is a stronger base because it's lone pair of electrons is available to react. In aniline, the electron pair is partially tied up in resonance and less available.

 

Pyridine is a stronger base because it's lone pair of electrons is available to react. The electron pair cannot be involved in the ring resonance since it is in an sp² hybrid orbital that is perpendicular to the ring. In aniline, the electron pair is partially tied up in resonance and less available.

Pyrrolidine is a stronger base because it's lone pair of electrons is available to react. The lone pair of electrons on pyrrole will be in a p-orbital. This will make the molecule aromatic (6 pi electrons in the ring). If these electrons acted as a base to make a new bond to H, the molecule would lose aromaticity.

Exercise \(\PageIndex{2}\)

Show using resonance structures why amines are much more basic than amides.

Answer

In amides, the nitrogen lone pair is delocalized with partial double bond character, therefore it is less available to react than in an amine.