Acyl chlorides

What are acyl chlorides also known as?

Acid chlorides

How are acyl chlorides prepared?

Carboxylic acids area chlorinated with SOCl₂ (sulfur dichloride oxide)

Give the general reaction for the production of acyl chlorides

Carboxylic acid + SOCl₂ → Acyl chloride + SO_{2 (g)} + HCl_(g)

What should be remembered about the preparation of acyl chlorides regarding safety?

The reaction should be carried out in a fume cupboard as the products are harmful

Show the preparation of propanoyl chloride from propanoic acid

How should acyl chlorides be named?

1. Remove ‘-ic acid’ from carboxylic acid and replace with ‘-yl’

2. Follow with halogen with -ide ending

Name the structure

Butanoyl bromide

Name the structure

2-methyl butanoyl chloride

Name the compound:

4-ethyl-2-methylhexanoyl chloride

What are the 4 physical properties of acyl chlorides

• Form colourless liquids

• Have a pungent odour

• Creates fumes in moist air

• Are readily hydrolysed to form a carboxylic acid and halogen acid

An acyl chloride like ethanoyl chloride is a colourless fuming liquid. Explain its properties

• The strong smell is a mixture of vinegar (ethanoic acid) and acrid smell of HCl gas

• Smell and fumes due to reactions with water vapour in the air

What is the reactivity of acyl chlorides like and why are they very useful in organic synthesis?

Acyl chlorides are extremely reactive and are more acidic than carboxylic acids

• They are useful because they can easily be converted into carboxylic acid derivatives such as esters and amides, with good yields

Describe the reaction of acyl chlorides with nucleophiles

Acyl chlorides lose their chloride ion whilst retaining the C=O double bond

Summarise the overall reaction of acyl chlorides

Name the 3 types of reactions of acyl chlorides

• Acyl chloride + alcohol → ester + HCl

• Acyl chloride + phenol → ester + HCl

• Acyl chloride + water → carboxylic acid + HCl

Give the advantage of making esters with acyl chlorides and alcohol rather than carboxylic acid and alcohol

Esterification through an alcohol and carboxylic acid is reversible and has a low yield

• Alcohols will readily react with acyl chlorides to produce esters

  • The yield is much higher and the reaction is not reversible

Show the formation of propyl ethanoate

Explain the advantage of using acyl chlorides and acid anhydrides instead of carboxylic acids when making esters from phenols

Carboxylic acids are not reactive enough to form esters with phenols as the reaction is incredibly slow

• Acyl chlorides and acid anhydrides are both more reactive than carboxylic acids and form phenol esters without needing an acid catalyst

Show the formation of phenyl ethanoate

Explain the reaction of acyl chlorides with water

When water is added to an acyl chloride, a violent reaction takes place and dense steamy hydrogen chloride fumes are formed

• A carboxylic acid is formed

Show the reaction of acyl chlorides with water