Alcohols with acyl chlorides
Introduced| English | Meaning |
|---|---|
| ester/ˈestə/ | An organic compound containing a carbonyl group bonded to an oxygen atom that is bonded to another carbon group. |
| acyl chloride/əˈkɪl ˈklɔːraɪd/ | An organic compound containing a carbonyl carbon bonded to a chlorine atom and another carbon group or hydrogen. |
| esterification/ˌestəˌrɪfɪˈkeɪʃn/ | A reaction that forms an ester, commonly by reacting an alcohol with a carboxylic acid. |
| by-product/baɪ ˈprɒdʌkt/ | A secondary product formed alongside the main intended product of a process. |
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.
Acyl chloride with alcohol route
Follow nucleophilic acyl substitution to an ester.
An alcohol reacting with an acyl chloride gives:
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The alcohol's –OH reacts with the acyl chloride to form an ester, releasing HCl.
An acyl chloride reacts with an alcohol to form an ______.
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Releasing hydrogen chloride gas.
Carboxylic acids are more reactive than acyl chlorides.
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False. Acyl chlorides are more reactive than carboxylic acids, because chloride is a good leaving group and the carbonyl carbon is strongly δ+.
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
Compared with using a carboxylic acid, making an ester from an acyl chloride is:
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Acyl chlorides are very reactive, so esterification with them is fast and goes essentially to completion.
Ethanol + ethanoyl chloride gives:
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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
- an alcohol + acyl chloride → ester (+ HCl)
- this is faster and more complete than using a carboxylic acid
- e.g. ethanol + ethanoyl chloride → ethyl ethanoate