Alcohols with acyl chlorides
Vocabulary
| English | Chinese | Pinyin |
|---|---|---|
| ester | 酯 | zhǐ |
| acyl chloride | 酰氯 | xiān lǜ |
| esterification | 酯化 | zhǐ huà |
| by-product | 副产物 | fù chǎn wù |
A faster way to esters 酯
- At A Level, an alcohol gains one more reaction.
- It reacts with an acyl chloride 酰氯 to make an ester.
- This works faster and more completely than using a carboxylic acid.
Explore
Acyl chloride with alcohol route
Follow nucleophilic acyl substitution to an ester.
Practice
An alcohol reacting with an acyl chloride gives:
The alcohol's –OH reacts with the acyl chloride to form an ester, releasing HCl.
Practice
An acyl chloride reacts with an alcohol to form an ______.
Releasing hydrogen chloride gas.
Practice
Acyl chlorides are more reactive than carboxylic acids.
The chlorine is a good leaving group.
The reaction
- An alcohol + an acyl chloride → an ester (plus fumes of $\text{HCl}$).
- It is faster and more complete than esterification 酯化 with a carboxylic acid.
- E.g. ethanol + ethanoyl chloride → ethyl ethanoate + HCl.
An acyl chloride reacts with an alcohol to form an ester
Practice
Compared with using a carboxylic acid, making an ester from an acyl chloride is:
Acyl chlorides are very reactive, so esterification with them is fast and goes essentially to completion.
Practice
Ethanol + ethanoyl chloride gives:
The ester ethyl ethanoate forms, along with HCl fumes.
A cleaner esterification
- Acyl chlorides react rapidly with alcohols to give esters, with no catalyst needed.
- The only by-product 副产物 is hydrogen chloride gas.
Handle with care
- Acyl chlorides react violently with water and fume in moist air.
- They are far more reactive than the corresponding carboxylic acids.
You've got it
Key idea
- an alcohol + acyl chloride → ester (+ HCl)
- this is faster and more complete than using a carboxylic acid
- e.g. ethanol + ethanoyl chloride → ethyl ethanoate