27 Amines, amino acids and polymers

Question 1

What are amines?

Answer 1

Amines are organic compounds derived from ammonia, NH3, where one or more hydrogen atoms in ammonia have been replaced by a carbon chain or ring.

Question 2

What is an aliphatic amine?

Answer 2

In an aliphatic amine, the nitrogen atom is attached to at least one straight or branched carbon chain (alkyl group, R)

Question 3

What is an aromatic amine?

Answer 3

In an aromatic amine, each nitrogen atom is attached to an aromatic ring (aryl group, Ar)

Question 4

How are amines classified?

Answer 4

By the number of alkyl or aryl groups attached to the nitrogen atom.

Question 5

How many alkyl/aryl groups are attached to the nitrogen atom in primary, secondary and tertiary?

Answer 5

Primary- 1
Secondary- 2
Tertiary- 3

Question 6

Examples where amines are used?

Answer 6

• Serotonin: neurotransmitter, responsible for control of appetite, sleep, memory and depression
• Pseudoephedrine: Ingredient in decongestion medications e.g nose drops

Question 7

How do we name amines? (PRIMARY ONLY)

Answer 7

• When NH2 group is on carbon-1, we add suffix -amine e.g ethyl amine
• If NH2 isn’t on carbon 1 we add prefix amino- and a number is added to indicate position. E.g 2-aminobutane.

Question 8

How do we name amines? (SECONDARY&TERTIARY)

Answer 8

• When they contain the same alkyl group, the prefixes di- or tri- are used to indicate the number of alkyl groups attached to the nitrogen atom.
• When two or more different groups are attached to a nitrogen atom, the compound is named as a N-substituted derivative.

Question 9

How do amines behave as bases?

Answer 9

Amines behave as bases became the lone pair of electrons on the nitrogen atom can accept a proton.

Question 10

What do you get when propylamine reacts with HCl?

Answer 10

Propylammonium chloride

Question 11

What do you get when ethylamine reacts with H2SO4?

Answer 11

Ethylammonium sulfate

Question 12

How does ammonia act as a nucleophile in a substitution reaction?

Answer 12

Ammonia has a lone pair of electrons on the nitrogen atom which allows ammonia to act as a nucleophile in a substitution reaction.

Question 13

How are primary amines formed?

Answer 13

1) Ammonia + haloalkane = ammonium salt

2) Ammonium salt+ alkali = primary amine + salt + water

Question 14

What are the essential conditions needed for formation of primary amines?

Answer 14

• Ethanol is used as the solvent which prevents any substitution of the haloalkane by water to produce alcohols.
• Excess ammonia is used to reduce further substitution of the amine group to form secondary & tertiary amines.

Question 15

Why is the reaction unsuitable for making a pure primary amine?

Answer 15

• The product still contains a lone pair of electrons on the nitrogen atom that can react further with a haloalkane to form a secondary amine.

Question 16

How is the secondary amine formed?

Answer 16

1) Primary amine + haloalkane = Salt (di)

2) Salt + sodium hydroxide = secondary amine + salt + water

Question 17

How is phenylamine made?

Answer 17

1) Nitrobenzene + Tin + HCl -> Ammonium salt (phenylammonium chloride)
2) Phenylammonium chloride + NaOH -> Phenylamine

Question 18

What acts as a reducing agent in the preparation of aromatic amines?

Answer 18

Tin and hydrochloric acid

Question 19

What is an amino acid?

Answer 19

An amino acid is an organic compound containing both amine and carboxylic acid functional groups
RCH(NH2)COOH

Question 20

What does the reaction between an amino acid and hydrochloric acid produce?

Answer 20

A salt.

E.g ammonium salt

Question 21

What does the reaction between an amino acid and aqueous alkali produce?

Answer 21

Amino acid + aqueous alkali -> Salt + Water

Question 22

What is the reaction between an amino acid and alcohol called?

Answer 22

Esterification

Question 23

What is the reaction between an amino acid and alcohol produce?

Answer 23

Ester + Water

Question 24

What conditions are required for the esterification of amino acids?

Answer 24

Heating amino acid with alcohol in presence of concentrated sulfuric acid

Question 25

What does the reaction between acyl chloride and ammonia produce?

Answer 25

Primary amide + Ammonium Chloride

Question 26

What does the reaction between acyl chloride and primary amine produce?

Answer 26

Secondary amide and ammonium chloride

Question 27

In which molecules is optical isomerism found?

Answer 27

Optical isomerism is found in molecules that contain a chiral centre.

Question 28

What is the chiral centre?

Answer 28

The chiral centre is a carbon atom that is attached to four different atoms or group of atoms.

Question 29

What are optical isomers also known as?

Answer 29

Enantiomers

Question 30

With the exception of glycine, which type of amino acids contain a chiral centre?

Answer 30

a-amino acids

Question 31

What is condensation polymerisation?

Answer 31

A reaction in which two small molecules react together to form a larger molecule with a small molecule such as water being eliminated.

Question 32

In which two ways can polyesters be made?

Answer 32

1) From one monomer containing both a carboxylic acid and alcohol group
2) From two monomers- one containing two carboxylic acid groups and other containing two alcohol groups

Question 33

In which two ways can polyamide be made?

Answer 33

1) From one monomer containing both a carboxylic acid (or acyl chloride) and an amine group
2) From two monomers, one containing two carboxylic acid groups (or acyl chlorides) and the other containing two amine groups.