6.1.11: Acyl chlorides

Question 1

Which functional group does acyl chloride contain?

Answer 1

R-COOCl

Question 2

What is the class of acyl chlorides?

Answer 2

Carboxylic acid derivatives where the -OH of the acid group has been replaced by a -Cl

Question 3

Describe a small acyl chloride.

Answer 3

• Small acyl chlorides are fuming (a visual gas or vapour being released) colourless liquids.
• Very reactive, with the chlorine atom being substituted for other groups.

Question 4

To make an acyl chloride, the -OH group on a carboxylic acid has to be substituted for a chlorine. How can this be done?

Answer 4

• One method is to use SOCl2, which is a liquid at room temperature and readily reacts with a carboxylic acid to form the desired product.
• Sulphur dioxide and hydrogen gases are also made.
• The acyl chloride can be separated from the reaction mixture using fractional distillation.

Question 5

Balanced symbol equation for the formation of ethanoyl chloride…

Answer 5

CH3COOH + SOCl2 –> CH3COCl + SO2 + HCl

Question 6

What will form when an acyl chloride reacts with an alcohol?

Answer 6

An ester.

Question 7

Why does the method of ester production involving an acyl chloride reacting with an alcohol produce a higher yield than using a carboxylic acid?

Answer 7

Because it is not a reversible reaction.

Question 8

Balanced symbol equation of the formation of an ester -ethyl ethanoate from an acyl chloride…

Answer 8

CH3COCl + CH3CH2OH –> CH3COOCH2CH3 + HCl

Question 9

Why must an acyl chloride method be used when forming an ester from a phenol? What is the downside

Answer 9

Because phenols do not react easily with carboxylic acids.

Question 10

What is the downside to using an acyl chloride method when forming an ester from a phenol?

Answer 10

The reaction is violent and produces corrosive forms of HCl

Question 11

What happens when a small acyl chloride such as ethanoyl chloride is added to water?

Answer 11

• It quickly hydrolyses to produce a carboxylic acid.

- This is a very exothermic reaction and misty fumes of HCl are given off.

Question 12

Balanced symbol equation of ethanoyl chloride being added to water?

Answer 12

CH3COCl + H2O –> CH3COOH + HCl

Question 13

What happens when an acyl chloride reacts with ammonia?

Answer 13

A primary amide is produced.

Question 14

How would you prepare ethanamide from an acyl chloride?

Answer 14

Ethanoyl chloride is added to a concentrated ammonia solution

• This quickly produces a mixture of solid ammonium chloride and ethanamide (observed as white smoke)
• Some of the product remains in a colourless solution.

Question 15

Ethanoyl chloride + ammonia solution balanced symbol equation…

Answer 15

CH3COCl + 2NH3 –> CH3CONH2 + NH4Cl

Question 16

What happens when an acyl chloride reacts with a primary amide?

Answer 16

• The product is a secondary amide.
• The nitrogen only has one hydrogen atom directly bound to it.
• The nitrogen also has two organic groups attached and is often called an N-substituted amide

Question 17

How could a white solid compound of N-ethylethanamide be made?

Answer 17

From ethanoyl chloride and a cold concentrated solution of ethylamine.

Question 18

Balanced symbol equation of N-ethylethanamide being made from ethanoyl chloride and ethylamine.

Answer 18

CH3COCl + CH3CH2NH2 –> CH3CONHCH2CH3 + HCl