Acyl Chlorides
Chemistry: Cambridge International A Level, topic 3.6.3
Formation of Acyl Chlorides
Acyl chlorides can be produced by reacting carboxylic acids with an inorganic compound called thionyl chloride (sulphur dichloride oxide).
Acyl chlorides
- Acyl chlorides can be derived from carboxylic acids.
- Acyl chlorides are also known as acid chlorides.
- Acyl chlorides have the general formula RCOCl.
Carboxylic acid to acyl chloride
- Acyl chlorides are produced from a reaction between sulphur dichloride oxide (SOCl2) and a carboxylic acid.
- Hydrogen chloride and sulphur dioxide gases are produced in the reaction.
Obtaining purity
- Fractional distillation can be used to remove excess reagents from the acyl chloride.
- Hydrogen chloride and sulphur dioxide are given off as gases.
Reactions of acyl chlorides
- Hydrolysis:
- R-COCl + H2O → R-COOH + HCl
- Reaction with alcohols to produce esters:
- R-COCl + C2H5OH → R-COOC2H5 + H2O
- Reaction with phenol:
- R-COCl + C6H5OH → R-COOC6H5
- Reaction with ammonia:
- R-COCl + NH3 → R-CONH2 + HCl
- Reaction with primary amines (R'NH2:
- R-COCl + R'N-H2 → R-CONH-R' + HCl
Acylation
Acylation reactions can be used to produce a variety of organic compounds, like amides.
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Compounds
- The above compounds are examples of acylated materials.
Nucleophilic addition-elimination
- The nucleophilic addition-elimination reaction happens with acyl chlorides and acid anhydrides.
- It is used to produce amides, carboxylic acids, and esters.
- The mechanism is on the next slide.
Mechanism
- This reaction can also be done with water or ammonia as nucleophile.
Test yourself on Acyl Chlorides
Acyl chlorides are produced by reacting sulphur dichloride oxide and a carboxylic acid.
What gases are produced as by-products in the reaction?Which of these are true about the formation of acyl chlorides?
In the mechanism of acyl chloride to an ester, what is removed?