# Explain why amides have significantly higher boiling points than amines of similar molar mass, yet amides are far less basic than amines.

> IB DP Chemistry Higher Level (2023 syllabus) — S3.2 Functional groups: classification of organic compounds · Explain · 4 marks

## Mark scheme (4 marks)

1. Amides can form intermolecular hydrogen bonds (N–H···O=C) that are stronger/more extensive than those in amines, leading to higher boiling points.
2. The carbonyl group in amides delocalises/withdraws the lone pair on nitrogen through resonance (conjugation), reducing its availability for hydrogen bonding donation — accept: the lone pair is part of a π system / delocalised into the C=O.
3. Because the lone pair on nitrogen in an amide is delocalised/less available, it cannot be readily donated to a proton (H⁺), so amides are much weaker bases (pKa of conjugate acid ≈ 0) compared with amines (pKa ≈ 10).
4. In amines, the nitrogen lone pair is localised and freely available to accept a proton, explaining their relatively high basicity, whereas in amides the same delocalisation that strengthens intermolecular interactions simultaneously reduces basicity.

## Key terms

- [amide](https://www.gradenine.co.uk/glossary/amide)
- [amine](https://www.gradenine.co.uk/glossary/amine)
- [boiling point](https://www.gradenine.co.uk/glossary/boiling-point)

## Related

- [Revision notes for IB DP Chemistry Higher Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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