Amines

Question 1

Classes of amines

Answer 1

Number of alkyl groups connected to N atom

Question 2

N-methylethanamine

Answer 2

CH₃CH₂NHCH₃

Question 3

Chemical test for an amine

Answer 3

Conc. HCl gives white fumes

Question 4

Why propan-1-amine can act as a base

Answer 4

It has a lone pair on the N so can accept a proton to form a dative covalent bond

Question 5

Equation showing propan-1-amine acting as a base

Answer 5

CH₃CH₂CH₂NH₂ + H₂O CH₃CH₂CH₂N⁺H₃ + OH^-

Question 6

Why butan-1-amine is a stronger base than ethanamine

Answer 6

Longer carbon chain
Greater electron releasing effect from alkyl group
Lone pair more available to accept a proton

Question 7

Why is phenylamine a weaker base than ammonia

Answer 7

The lone pair is partially delocalised into the benzene ring
Lone pair is less able to accept a proton

Question 8

Ammonia + bromopropane equation

Answer 8

CH₃CH₂CH₂Br + 2 NH₃ > CH₃CH₂CH₂NH₂ + NH₄Br

Question 9

Roles of ammonia in reaction with bromopropane

Answer 9

First acts as a nucleophile attacking 𝛿+ C to replace Br
Then acts as a base accepting a proton from bromopropane

Question 10

Reaction between ethanamine and bromopropane
Type

Answer 10

Nucleophilic substitution

Question 11

Reaction between ethanamine and bromopropane, Mechanism

Answer 11

ethanamine N lone pair > 𝛿+ C
C-Br > Br
N⁺-H > N⁺
(:Br^-)

Question 12

Reaction between ammonia and bromopropane
Type

Answer 12

Nucleophilic substitution

Question 13

Reaction between ammonia and bromopropane
Mechanism

Answer 13

NH₃ lone pair > 𝛿+ C
C-Br > Br
NH₃ lone pair > H
N⁺-H > N⁺
(+ :Br^-)
(+ NH₄Br)

Question 14

Why does NH₃ + bromopropane have a low yield

Answer 14

Further substitution occurs as product contains a lone pair so can act as a nucleophile
Unless an excess of NH₃ is used

Question 15

Use of quaternary ammonium salt and why

Answer 15

Fabric softener - coat fibres with positive charges allowing them to move past each other more easily

Question 16

Reduction of propanenitrile equation

Answer 16

CH₃CH₂CN + 4 [H] > CH₃CH₂CH₂NH₂

Question 17

2 examples of reducing agents in reduction of propanenitrile

Answer 17

H_{2 (g)} in a presence of a nickel catalyst
LiAlH₄

Question 18

Reduction of nitrobenzene equation

Answer 18

{o}^/NO₂ + 6 [H] > {o}^/NH₂ + 2 H₂O

Question 19

Reducing agent needed for reduction of nitrobenzene

Answer 19

Sn or Fe with conc. HCl

Question 20

3 reasons why phenylamine cannot be made by reducing bromobenzene with ammonia

Answer 20

C bonded to Br is not 𝛿+
NH₃ is a nucleophile
Lone pair on NH3 is repeller by the delocalised ring