Primary Amines (Cambridge (CIE) A Level Chemistry): Exam Questions

Propylamine is a colourless liquid that is used to manufacture a variety of chemicals including textile resins, drugs and pesticides. It can be produced by the reaction of 1-chloropropane with ammonia.

i) State the role of the ammonia in this reaction.

[1]

ii) Name the type of reaction that occurs in this synthesis of propylamine.

[1]

Use an appropriate chemical equation to explain why propylamine can be described as a Brønsted-Lowry base with water.

The reaction between 1-chloropropane and ammonia proceeds in two steps.

 Step 1 involves the formation of an intermediate.

Step 2 forms the final propylamine product.

 As the reaction proceeds, the bond angles around the nitrogen atom change. Explain these changes in the bond angles around the nitrogen atom.

Fig. 2.1 shows a reaction sequence to form an amine.

Fig. 2.1

i) Name compound A. 

[1]

 ii) Reaction 1 heats compound A under reflux with an ethanolic solution of potassium cyanide. 

Draw the mechanism for the reaction of compound A with the ethanolic solution of potassium cyanide to form compound B. 

• Identify the ion that reacts with compound A

• Draw the product of this reaction, compound B.

• Include all charges, partial charges, lone pairs and curly arrows.

[4]

In reaction 2, vapours of compound B are converted into compound C by reacting them with hydrogen gas over a nickel catalyst.

 Name the type of reaction that occurs in reaction 2. 

Compound C can also be produced in a single step from compound D.

i) Draw the displayed formula of compound D. 

[1] 

ii) State suitable reagents and conditions for reaction 3. 

[2]

Compound C is a primary amine as there is one alkyl chain attached to the nitrogen atom.

 Draw the skeletal formula of compound C's two isomers, which are also primary amines.

Butylamine is an organic compound used as an ingredient in the manufacture of pesticides.

One possible method of making butylamine from 1-chlorobutane is shown in Fig. 3.1.

Fig. 3.1

i) Deduce the type of reaction that occurs in reaction 1. 

[1]

 ii) State suitable reagents and conditions for reaction 1. 

[2]

Draw the mechanism for reaction 1 and label compound X in your answer. Include all necessary partial and full charges.

Compound X undergoes another reaction in reaction 2 before butylamine is formed.

i) Describe what occurs in reaction 2.  

[1]

ii) Give the molecular formula of compound Y.  

[1]

iii) The by-products Cl^- and compound Y can combine together to form compound Z. State the name of compound Z. 

[1]

Compound X is produced from cyclohexene. An amine which is a relatively weak base containing one nitrogen atom can be produced from compound X in one step. 

Outline a mechanism for the formation of compound X from cyclohexene. You will need to give suitable reagents in your answer. 

One condition that is needed to convert compound X into the amine molecule is that the reagent needs to be in excess.

i) State the reagent and any other required conditions for the reaction.

[2]

ii) Suggest why the reagent needs to be in excess.

[1]

Propylamine acts as a Brønsted-Lowry base when it reacts with water.

Suggest an equation to show how propylamine reacts when mixed with water.