# Carboxylic acid derivatives

> CIE A-Level Chemistry · CIE 9701
> Source: https://www.owlsprep.com/study/cie-9701-u26-overview/
> Weight: n/a

This unit explores core classes of carboxylic acid derivatives (esters, acyl chlorides, acid anhydrides, amides), key reactivity trends, and the widely used acylation reaction pathway central to organic synthesis.

**Prerequisites:** [Carboxylic acid structure and reactivity](https://www.owlsprep.com/study/cie-9701-u25-carboxylic-acids-overview/)

## Learning objectives

- Identify structures and apply correct nomenclature to all common classes of carboxylic acid derivatives
- Compare and predict reactivity of different derivatives based on the electrophilicity of the acyl carbon
- Explain mechanisms and products for nucleophilic acyl substitution and acylation reactions

## Unit at a Glance

This unit builds on your prior knowledge of carboxylic acids to study related compounds that have critical industrial (polymer production, food preservatives) and biological (protein amide bonds) roles. The learning sequence progresses from general properties and reactivity of all derivative classes to a deep dive into acylation, a key reaction used frequently in CIE exam synthesis questions.

This unit is split into two connected sub-topics:
- [Properties and reactions of carboxylic acid derivatives](https://www.owlsprep.com/study/cie-9701-u26-properties-and-reactions-of-carboxylic/) — Learn nomenclature, physical properties, reactivity trends, and core reactions of all common carboxylic acid derivative classes.
- [Acylation reactions](https://www.owlsprep.com/study/cie-9701-u26-acylation-reactions/) — Master nucleophilic acyl substitution mechanisms and key applications of acylation in organic synthesis.

## Common pitfalls

- **Wrong:** Reversing the reactivity order of carboxylic acid derivatives
  - Why it fails: Many students forget that electron-donating groups reduce the electrophilicity of the acyl carbon, slowing nucleophilic attack
  - Correct: Remember reactivity from highest to lowest: acyl chlorides > acid anhydrides > esters > amides
- **Wrong:** Drawing nucleophilic addition instead of substitution for acyl reactions
  - Why it fails: Acyl derivatives have a good leaving group attached to the acyl carbon, unlike aldehydes/ketones
  - Correct: Always include the leaving group departure step to form a substituted acyl product

## Cheatsheet

| Concept | Key Summary |
| --- | --- |
| Reactivity order | $\text{Acyl chloride} > \text{Acid anhydride} > \text{Ester} > \text{Amide}$ |
| General nucleophilic acyl substitution | $RCOZ + Nu^- \rightarrow RCONu + Z^-$ |
| Acidic ester hydrolysis | Reversible, produces carboxylic acid + alcohol |
| Alkaline ester hydrolysis | Irreversible, produces carboxylate salt + alcohol |
| Acylation definition | Transfer of an acyl group ($RCO-$) to a nucleophile via nucleophilic acyl substitution |

## What's next

Begin this unit by learning the core properties and reactivity trends of carboxylic acid derivatives to build a foundation for more complex reaction mechanisms. Once you complete this sub-topic, you will move on to study acylation reactions in depth. After finishing the entire unit, you can proceed to the next topic on nitrogen compounds.

- [Properties and reactions of carboxylic acid derivatives](https://www.owlsprep.com/study/cie-9701-u26-properties-and-reactions-of-carboxylic/)
- [Acylation reactions](https://www.owlsprep.com/study/cie-9701-u26-acylation-reactions/)
- [Organic synthesis](https://www.owlsprep.com/study/cie-9701-u27-overview/)

---

From [OwlsPrep](https://www.owlsprep.com) — free study guides for A-Level, IB, AP and IGCSE, written against the official syllabus. Canonical page: https://www.owlsprep.com/study/cie-9701-u26-overview/