Amines and polymers

Question 1

Naming primary amines

Answer 1

When the NH2 group is on the end of the chain you can add the suffix -amine to the end of the alkyl chain, i.e. ethylamine. When the amine group is not on the first carbon, the amine is named using the prefix amino and a number is added to indicate the position of the amine group, i.e. 2-aminobutane.

Question 2

Naming secondary or tertiary amines

Answer 2

When they contain the same alkyl group, you can use the prefex di- or tri- to indicate the number of alkyl groups attached to the nitrogen atom, i.e.e dimethylamine. When two or more different groups are attached to a nitrogen atom, the compound is named as a N-substituted derivative. For example, N-methylpropylamine. For a tertiary amine it might be N-ethyl-N-methylpropylamine

Question 3

Primary amine

Answer 3

Attached to two hydrogens and a R-group

Question 4

Secondary amine

Answer 4

Attached to one hydrogen and two R-groups

Question 5

Tertiary amine

Answer 5

Attached to three R-groups

Question 6

Aliphatic amine

Answer 6

When the nitrogen atom is attached to at least one straight or branched carbon chain

Question 7

Aromatic amine

Answer 7

When the nitrogen is attached to an aromatic ring

Question 8

Amines as bases

Answer 8

Amines behave as bases in chemical reactions as the lone pair of electrons on the nitrogen atom accepts a proton.

Question 9

What happens when an amine accepts a proton

Answer 9

A dative covalent bond is formed between the lone pair of electrons on the nitrogen atom and the proton

Question 10

Salt formation with amines

Answer 10

Amines are bases which neutralise acids to make salts

CH3NH2 + HCl –> CH3NH3+Cl-

Question 11

Formation of primary amine

Answer 11

A haloalkane reacts with ammonia to form an ammonium salt, i.e. propylammonium chloride. This reacts with an aqueous alkali such as NaOH to form an amine, i.e. propylamine. Ethanol is used as a solvent, to prevent any substitution of the haloalkane with water to produce an alcohol. Excess ammonia is used, to prevent further substitutions of the amine group to form secondary and tertiary amines.

Question 12

Formation of secondary amines

Answer 12

The salt formed when the ammonia reacts with the haloalkanes can react with another haloalkane to form an ammonium salt i.e (CH3CH2CH2)2NH2+Cl-. This reacts with NaOH to form a secondary amine, NaCl and H20

Question 13

Formation of tertiary amines

Answer 13

From further substitutions of the secondary amine salt

Question 14

Preparation of aromatic amines

Answer 14

Nitrobenzene is heated under reflux with tin and HCl to form the ammonium salt, phenylammonium chloride. This then reacts with excess NaOH to form phenylamine. Tin and HCl are the reducing agents

Question 15

Easy way to make an aliphatic amine

Answer 15

React with excess ammonia in ethanol

Question 16

General formula of an alpha amino acid

Answer 16

RCH(NH2)COOH

Question 17

Reactivity of amino acids

Answer 17

As they have both the acidic COOH and basic NH2, amino acids have similar reactions to both carboxylic acids and amines and can react with both acids and bases

Question 18

Reaction of the amine group in amino acids

Answer 18

Will react with acids to form an ammonium salt. When reacting with HCl, the NH2 group turns into NH3+ and Cl- is also formed

Question 19

Reaction of the carboxylic acid group in amines with an aqueous alkali

Answer 19

Forms a salt and water. For example, when it reacts with NaOH the COOH turns into COO-Na+, water is also produced

Question 20

Reaction of the carboxylic acid group in amino acids with alcohols

Answer 20

The amino acids are esterified by heating the alcohol in concentrated sulphuric acid. Water is also produced

Question 21

Amides

Answer 21

Are the product of a reaction between an acyl chloride with ammonia and amines. There is a carbon double bond with an oxygen atom, the carbon is also bonded to a nitrogen

Question 22

What is required for an optical isomer (amino acid)

Answer 22

Must have a chiral centre, which leads to the existence of two non-superimposable mirror image structures

Question 23

What’s a chiral centre

Answer 23

A carbon atom which is attached to four different types of atoms

Question 24

Drawing optical isomers

Answer 24

The two structures are drawn as mirror images of each other

Question 25

Condensation polymerisation

Answer 25

The joining up of monomers with the loss of water or HCl

Question 26

Polyesters

Answer 26

Can be made from one monomer containing both a carboxylic acid and an alcohol group, or from two monomers; one containing two carboxylic acid groups and the other containing two alcohol groups. Involves the loss of water

Question 27

Polyamides

Answer 27

Polyamides can be made from one monomer containing both a carboxylic acid (or acyl chloride) and an amine group, or from two monomers, one containing two carboxylic acid groups (or acyl chloride) and an another containing two amine groups. If a carboxylic acid group is used H2O is produced, if alcyl chloride is used HCl is produced

Question 28

Hydrolysing condensation polymers

Answer 28

Polyesters and polyamides can be hydrolysed using a hot aqueous alkali such as sodium hydroxide or by hot aqueous acid such as HCl

Question 29

Acid hydrolyses of polyesters

Answer 29

The monomers are reformed

Question 30

Alkali hydrolyses of polyesters

Answer 30

The alcohol is reformed, The carboxylic acid group reacts with the alkali to form COO-Na+

Question 31

Acid hydrolyses of polyamides

Answer 31

The monomers are reformed but it is NH3+ instead of NH2

Question 32

Alkali hydrolyses of polyamides

Answer 32

The amine is reformed, the carboxylic acid group reacts with the alkali to form COO-Na+

Question 33

What is specific to an addition polymer

Answer 33

Contains a C=C double bond

Backbone of polymer is a continuous chain of carbon atoms

Question 34

What is specific to a condensation polymer

Answer 34

Two monomers, each with two of the same functional groups or one monomer with two different functional groups
Polymer contains ester or amide linkage