Acyl chlorides
Introduced| English | Meaning |
|---|---|
| acyl chloride/əˈkɪl ˈklɔːraɪd/ | An organic compound containing a carbonyl carbon bonded to a chlorine atom and another carbon group or hydrogen. |
| nucleophile/ˈnjuːklɪɒfaɪl/ | An electron-pair donor that forms a covalent bond to an electron-deficient centre. |
| addition–elimination/əˈdɪʃn ɪˌlɪmɪˈneɪʃn/ | A reaction mechanism in which a group first adds to a molecule and another group is then eliminated. |
| amide/əˈmaɪd/ | An organic compound containing a carbonyl group bonded to a nitrogen atom. |
| leaving group/ˈliːvɪŋ ɡruːp/ | leaving group |
The most reactive derivatives
- Acyl chlorides 酰氯 are made from carboxylic acids and are very reactive.
- They react with many nucleophiles 亲核试剂, always releasing HCl.
- They follow an addition–elimination 加成消去 mechanism.
Acyl chloride reaction map
Follow why acyl chlorides are reactive acylating agents.
Acyl chlorides react vigorously with water to give a carboxylic acid and ______ chloride gas.
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Misty fumes of HCl form.
Reactions (all give HCl)
| Reactant | Product |
|---|---|
| water | the carboxylic acid |
| an alcohol | an ester |
| phenol | an ester |
| ammonia | an amide 酰胺 |
| a 1°/2° amine | an amide |
Addition-elimination mechanism of an acyl chloride
An acyl chloride reacting with ammonia gives:
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Ammonia (or a 1°/2° amine) reacts with an acyl chloride to give an amide.
An acyl chloride reacting with water gives:
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Hydrolysis of an acyl chloride regenerates the carboxylic acid (very vigorously).
Match each term to its meaning.
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Each item links the term to its correct meaning.
Addition–elimination
- A nucleophile adds to the slightly positive carbonyl carbon → a tetrahedral intermediate.
- Then the C=O reforms and $\text{Cl}^-$ leaves as HCl (elimination).
- Ease of hydrolysis: $\text{acyl chloride} \gg \text{alkyl chloride} \gg \text{aryl chloride}$ (the aryl C–Cl is strengthened by the ring).
Acyl chlorides react with many nucleophiles
The reactions of acyl chlorides follow which mechanism?
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A nucleophile adds to the carbonyl carbon; the C=O reforms and Cl⁻ leaves as HCl.
The order of ease of hydrolysis is:
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Acyl chlorides hydrolyse violently, alkyl slowly, and aryl chlorides not at all (ring-strengthened C–Cl).
The most reactive derivative
- Acyl chlorides react vigorously with water, alcohols, ammonia and amines.
- The chlorine is an excellent leaving group 离去基团, which is why they are so reactive.
You've got it
- acyl chlorides are very reactive; with water → acid, alcohol/phenol → ester, ammonia/amine → amide (all + HCl)
- mechanism = addition–elimination (nucleophile adds to the carbonyl carbon, then HCl is eliminated)
- hydrolysis ease: acyl ≫ alkyl ≫ aryl chloride