Organic chemistry- acyl chlorides

Question 1

how are acyl chlorides prepared?

Answer 1

reaction between parent carboxylic acid and the thionyl chloride, SOCl2. SO2(g) and HCl gases are also formed. This reaction should be in a fume cupboard as products are harmful

Question 2

why are acyl chlorides useful in organic synthesis?

Answer 2

they are very reactive as they can be easily converted into carboxylic acid derivatives, such as esters and amides with good yields. Acyl chlorides react with nucleophiles by losing the chloride ion whilst retaining the C=O double bond

Question 3

what is formed in the reaction between an alcohol and acyl chloride?

Answer 3

The reaction forms ester and hydrogen chloride.

Question 4

Describe the reaction of acyl chlorides with phenols

Answer 4

Acyl chlorides are much more reactive than carboxylic acids so the reaction forms phenyl esters and hydrogen chloride unlike carboxylic acids. The reaction doesn’t require a catalyst

Question 5

Describe the reaction of acyl chlorides with water

Answer 5

a violent reaction takes place, steamy hydrogen chloride fumes and carboxylic acids are formed.

Question 6

Describe the reaction of acyl chlorides with ammonia and amines

Answer 6

ammonia and amines act as nucleophiles by donating the lone pair on the nitrogen atom to an electron efficient species. This forms amides. Ammonia forms a primary amide where the nitrogen atom is attached to one carbon atom.

Question 7

Describe the reaction of acyl chlorides with ammonia

Answer 7

Ammonia forms a primary amide where the nitrogen atom is attached to one carbon atom.

Question 8

Describe the reaction of acyl chlorides with a primary amine

Answer 8

a secondary amide is formed where the nitrogen atom is attached to two carbon atoms.

Question 9

Describe acid anhydrides

Answer 9

• reacts in a similar way to acyl chlorides with alcohols, phenols, water, ammonia and amines
• less reactive than acyl chlorides and are useful for some lab preparations where acyl chlorides may be too reactive.

Question 10

Describe the mechanism of the reaction between acyl chlorides and nucleophiles

Answer 10

addition:
-lone pair of electrons from nucleophile is attracted to the delta positive carbon atom in the C=O group of the acyl chloride.
Elimination:
-lone pair of electrons on oxygen reforms C=O bond causing removal of chloride ion. A proton is then lost to complete the elimination. The loss of the Cl- followed by H+.
Mechanism is called nucleophilic addition-elimination