Amines

Question 1

What is the amine group?

Answer 1

NH₂

Question 2

By what mechanism are amines formed?

Answer 2

Nucleophilic substitution with an ammonia nucleophile

Question 3

How do you make a primary amine from a haloalkane?

Answer 3

Nucleophilic substitution with excess NH₃

Question 4

Why can primary amines go on to from secondary, tertiary and quaternary amines?

Answer 4

NH₂ group attached to carbon chain has a lone pair which acts as a nucleophile and reacts with the haloalkane

Question 5

What is the by product of the reaction of bromoethane with NH₃?

Answer 5

NH₄⁺Br^-

ammonium bromide

Question 6

What are the uses of quaternary amines?

Answer 6

Conditioner

Reduces build up of static electricity by acting as a cationic surfactant

Question 7

Is KCN or HCN better for forming CN^- nucleophiles?

Answer 7

KCN

HCN is toxic

Question 8

By what process are amines formed from nitriles?

Answer 8

Reduction

Question 9

What is the reducing agent to form amines from nitriles?

Answer 9

1. LiAlH₄ (lithium tertahydridoaluminate) in ether

NaBH₄ is not strong enough

2. Hydrogen with nickel catalyst

Question 10

What are the 3 types of amines used a bases?

Answer 10

1. primary amine
2. ammonia
3. aromatic amine

Question 11

List 3 amines from the strongest base to the weakest

Answer 11

primary amine

ammonia

aromatic amine

Question 12

Why are primary amines good bases?

Answer 12

Inductive effect pushes electrons from the alkyl group to the lone pair, making the lone pair more available

Question 13

Why are aromatic amines bad bases?

Answer 13

Lone pair becomes delocalised onto the benzene ring therefore making the lonen pair less available

Question 14

Describe the trend in the solubility of amines and Mr

Answer 14

Solubility decreases as Mr increases

Question 15

Are amines soluble?

Answer 15

All are soluble in organic solvents

Lighter amines soluble in water due to hydrogen bonding

Question 16

What is produced when an amine dissolves in water?

Answer 16

Weak alkaline solution

Question 18

What is produced when an amine reacts with an acid?

Answer 18

A salt

Question 19

What conditions are needed to make a primary amine through nucleophilic substitution?

Answer 19

Reflux in excess, alcoholic solution under pressure

Question 20

Why is excess NH₃ required to make a primary amine?

Answer 20

Ensures all haloalkane molecules react with ammonia rather then the newly produced amine

Question 21

What is the reaction and conditions needed to form an aromatic amine from an aromatic nitro compound?

Answer 21

Reduction

Reflux with tin and conc HCl