Unit 3.4.7 - Amines

Question 1

What are amines?

Answer 1

Where one or more of the hydrogens in ammonia is replaced with a functional group

Question 2

What is a primary amine?

Answer 2

Where one hydrogen has been replaced in ammonia

Question 3

What is a secondary amine?

Answer 3

Where two hydrogens have been replaced in ammonia

Question 4

What is a tertiary amine?

Answer 4

Where three hydrogens have been replaced in ammonia

Question 5

What is a quaternary ammonium ion?

Answer 5

Where a forth functional group had been added to a tertiary amine

Question 6

What are quaternary ammonium salts?

Answer 6

Where a positively charged ammonium ion has bonded with a negatively charged ion

Question 7

What types of amines smell similar to ammonia?

Answer 7

Small amines

Question 8

What do small amines smell of?

Answer 8

Slightly fishy

Question 9

What do large amines smell of?

Answer 9

Very fishy

Question 10

What suffix is used to name amines?

Answer 10

-amine

Question 11

What suffix is used to name quaternary ammonium ions?

Answer 11

-amine ion

Question 12

What is the difference between aromatic amines and aliphatic amines?

Answer 12

Aromatic amines contain a benzene ring where as aliphatic ones don’t

Question 13

What is an aromatic amine?

Answer 13

An amine that contains a benzene ring

Question 14

What is an aliphatic amine?

Answer 14

An amine that doesn’t contain a benzene ring

Question 15

Amines can act as bronsted-lowry …. ? And why?

Answer 15

Bronsted-lowry bases as they can accept protons as there is a lone pair of electrons on the nitrogen

Question 16

The strength of an anime as a base depends on what?

Answer 16

How available the nitrogen’s lone pair of electrons is , the more available the more likely it is to accept a proton and the stronger a base it will be

Question 17

What is the order of the strength of these bases: ammonia, primary aliphatic amines and aromatic amines, from least to most?

Answer 17

Aromatic amines, ammonia, primary aliphatic amines

Question 18

Why are aromatic amines the weakest base?

Answer 18

The benzene ring draws electrons towards itself and the nitrogen’s lone pair gets partially delocalised into the ring, so the electron density on the nitrogen decreases and so the pair is much less available to accept a proton making it a weak base

Question 19

Why is ammonia a stronger base than aromatic bases?

Answer 19

They don’t have any aromatic groups to pull the lone pair of electrons away from the nitrogen

Question 20

Why are primary aliphatic amines the strongest base?

Answer 20

The alkyl group pushes the electron density onto the nitrogen atom and so its electron density increases and so the lone pair is more available to accept a proton making it a strong base

Question 21

What three ways can you produce aliphatic amines?

Answer 21

1.) By heating a haloalkane with excess ammonia or amine 2.) Reducing a nitrile 3.) Reflux a nitrile with sodium metal and ethanol

Question 22

What is produced when you heat haloalkanes with excess ammonia?

Answer 22

A mixture of primary, secondary and tertiary amines and quaternary ammonium salts

Question 23

How would you separate a mixture of primary, secondary and tertiary amines and quaternary ammonium salts?

Answer 23

By fractional distillation

Question 24

What is the name for the mechanism between ammonia and haloalkanes?

Answer 24

Nucleophilic substitution

Question 25

Why do you produce a mixture of primary, secondary and tertiary amines and quaternary ammonium salts when you react ammonia with haloalkanes?

Answer 25

Because further hydrogens are substituted

Question 26

Give the five steps in the reaction between ammonia and haloalkanes.

Answer 26

1.) The NH₃ is attracted to the slightly positive carbon and it attacks it donating a pair of its electrons forming a blind with the carbon 2.) As carbon can only have four bonds, it cause the C-X bond to break releasing X⁻ and leaving an alkyl ammonium salt 3.) This cause the hydrogen to break of the alkyl ammonium salt and join the ammonia to form NH₄⁺ 5.) This leaves a primary amine, and NH₄X

Question 27

What is the nucleophile in the reaction between ammonia and haloalkanes? and why?

Answer 27

Ammonia - it has a lone pair of electrons

Question 28

Why do you get further substitutions after reacting ammonia with a haloalkane?

Answer 28

The primary amine still has a lone pair of electrons

Question 29

Why does substitution stop at quaternary ammonium salts?

Answer 29

There are no more lone pair of electrons

Question 30

What are surfactants?

Answer 30

Compounds which are partly soluble and partly insoluble in water

Question 31

What are surfactants with a positive charge called?

Answer 31

Cationic surfactants

Question 32

What can be used as cationic surfactants?

Answer 32

Quaternary ammonium salts

Question 33

Which quaternary ammonium salts are suitable to use as cationic surfactants? And why?

Answer 33

Ones with at least one long hydrocarbon tails the long hydrocarbon chain is insoluble in water and positively charged head is soluble

Question 34

Name two uses of cationic surfactants?

Answer 34

Fabric conditioner and hair products

Question 35

Why are cationic surfactants used in fabric conditioner or hair products?

Answer 35

When the hair or fabric gets wet they pick up negative charges on their surface, the positively charged part of the surfactant is attracted to his and forms a coating over the surface, this coating prevents the build up of static electricity to keep fabric smooth or hair flat

Question 36

How can you produce a primary aliphatic amine by reduction?

Answer 36

Mix a nitrile with a strong reducing agent like LiAlH₄, followed by dilute acid

Question 37

How can you produce a primary aliphatic amine by reflux?

Answer 37

Reflux a nitrile with sodium metal and ethanol

Question 38

As both LiAlH₄ and Na is too expensive what method is used in industry to make primary aliphatic amines? And what is required for it?

Answer 38

Catalytic hydrogenation by using a metal catalyst such as platinum or nickel at a high temperature and pressure

Question 39

How can you produce aromatic amines?

Answer 39

By reducing a nitro compound such as nitrobenzene, by heating it under reflux with tin metal and concentrated HCl

Question 40

What are the two steps in producing aromatic amines?

Answer 40

1.) Heat the nitro compounds with tin metal and concentrated hydrochloric acid under reflux to make a salt 2.) Add sodium hydroxide to turn the salt not an aromatic amine

Question 41

Draw the general structure of ammonia, a primary amine, a seconday amine, a tertiary amine and a quaternary ammonium ion

Answer 41

Question 42

Draw an example of a cationic surfactant.

Answer 42

Question 43

Draw the equation for reducing ethanenitrile used LiAlH₄

Answer 43

Question 44

Draw the equation of the reduction of a nitrobenzene to a aromtic amine.

Answer 44