Mr Cole Chemistry

Forming Aliphatic Amines Questions

Synthesis of Aliphatic Amines

Amines Worksheet
1. It is possible to make ethylamine from chloroethane.
a) Write an equation for the formation of ethylamine from chloroethane.
CH3CH2Cl + 2NH3
→
CH3CH2NH2 + NH4Cl
b) State the conditions required for the reaction and explain why that condition is required.

Excess ammonia is required.

This prevents further substitutions where the primary amine product (CH3CH2NH2) acts as a nucleophile and reacts with more chloroethane. This would otherwise produce a mixture of secondary/tertiary amines and quaternary ammonium salts.

c) Outline the mechanism for the reaction to produce ethylamine.
Mechanism for ethylamine synthesis
2. Propylamine can also be made from chloroethane in a two-step process.
a) Complete the process below: Chloroethane → …………… → Propylamine

Chloroethane → Propanenitrile → Propylamine

b) Write the equation for the first step of the reaction.
CH3CH2Cl + KCN
→
CH3CH2CN + KCl
c) Write the conditions for the first step of the reaction.

Aqueous and Ethanolic potassium cyanide, heated under reflux.

d) Write the equation for the second step of the reaction.

Using a reducing agent:

CH3CH2CN + 4[H]
→
CH3CH2CH2NH2

Or using catalytic hydrogenation:

CH3CH2CN + 2H2
→
CH3CH2CH2NH2
e) State the conditions for the second step of the reaction.

LiAlH4 in dry ether (for the first equation).

OR

Nickel catalyst and heat (for catalytic hydrogenation).

f) State the name of the mechanism for step 1 and outline the mechanism.

Nucleophilic Substitution

Mechanism for Step 1
g) State the name of the type of reaction for step 2.

Reduction

3. 2-chloropropane can react with methylamine.
a) Draw the main organic product.
Product Structure
b) State the conditions required for the reaction and explain why that condition is required.

Excess methylamine is required.

This prevents further substitutions where the secondary amine product reacts with the remaining 2-chloropropane.

c) Outline the mechanism for the reaction to produce the main organic product.
Mechanism for reaction
4. 6-bromohexylamine can undergo a nucleophilic substitution reaction with ammonia.
a) State the name of the product; draw the product; and state the conditions of the reaction.

1,6-diaminohexane (or hexan-1,6-diamine)

1,6-diaminohexane structure

Conditions: Ammonia in large excess, heat, ethanolic solution.

b) Cyclic impurities are likely to form. Draw the first possible impurity (6 carbon atoms) and explain how it arises.
Cyclic impurity 1

The amine group on carbon 1 reacts with the halogen group on carbon 6 of the same molecule (intramolecular substitution).

c) Draw the second possible impurity (12 carbon atoms) and explain how it arises.
Cyclic impurity 2

Two molecules of 6-bromohexylamine react together to form a larger ring structure.

5. When 1-bromobutane reacts with ammonia, a mixture of organic products is formed.
Product 1: Butylamine
Butylamine

Ammonia substitutes the bromine atom in the bromobutane.

Product 2: Dibutylamine
Dibutylamine

The nitrogen on the butylamine substitutes the bromine atom on another molecule of bromobutane.

Product 3: Tributylamine
Tributylamine

The nitrogen on the dibutylamine substitutes the bromine atom on another molecule of bromobutane.

Product 4: Tetrabutylammonium bromide
Tetrabutylammonium

The nitrogen on the tributylamine substitutes the bromine atom on another molecule of bromobutane, forming a quaternary ammonium salt.

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