6D - Amines, amides & polyamides

Question 1

Define Amine

Answer 1

Amine = A NH₃ group where one or more of the Hs have been substituted with an alkyl group

Question 2

Structure of a primary, secondary and tertiary amine.

How many alkyl groups does each have?

Answer 2

Question 3

Define:

Aliphatic amine

Aromatic amine

Answer 3

Aliphatic amine = Nitrogen atom attached to at least one branched carbon chain

Aromatic amine = Nitrogen atom attached to an aromatic ring

Question 4

Name + clssify what type of amine this this

Answer 4

Ethylamine

Primary amine

Question 5

Name + clssify what type of amine this this

Answer 5

2-Aminopropane

Secondary amine

Question 6

Name + clssify what type of amine this this

Answer 6

Ethane-1,2-diamine

Primary amine

Question 7

Name + clssify what type of amine this this

Answer 7

Phenylamine

Question 8

Name + clssify what type of amine this this

Answer 8

N-methylpropylamine

N is for the shorter alkyl chain present when it’s a seondary amine

Question 9

Name + clssify what type of amine this this

Answer 9

Triethylamine

Tertiary amine

Question 10

What intermolecuar forces are present in amines?

Answer 10

Mainly - most important:

• London forces
• Hydrogen bonding

Also has permanent dipole-dipole interactions

Question 11

Strength in london forces in relation to the size of the amine?

Answer 11

Larger amine, no’ of electrons increase ∴ stronger longer forces but compromise the H bonding in secondary & tertiary structures.

• Increased branching reduces SA available for H bonds to form

Question 12

Question:

Compare boiling points

Answer 12

• Decreases from primary → secondary → tertiary
• Diethylamine = lowest as most branches ∴ weakest london forces out of the 3
• 1-aminobutane = highest as longest alkyl group ∴ increases the size of the moledule, least branches ∴s strongest london forces ∴ highest boiling point

Question 13

Trend of solubility of amines

Answer 13

Gets less solution as the amine increases in size - alkyl group increases, they’re hydrophobic. Small ainesa re very solution in water

Question 14

Why can amines act as bases?

Answer 14

• Ammonia molecule can accept a proton because N has a lone pair that can donate H⁺ to form a sative covalent bond

NH₃ + H⁺ ⇌ NH₄⁺

Amine + Acid → Alkylammonium salt

Question 15

Amine + Acid → ?

Answer 15

Amine + Acid → Alkylammonium salt

Question 16

Draw the structure of the alkylammonium ion

Answer 16

Question 17

What do amines smell like?

Theie volatility?

Answer 17

Relatively voltalile

Smell FISHY

Question 18

2 ways of preparing primary amine

Reagents + conditions

Answer 18

Method 1:

​Nitrile + H₂ → Amine

R = Nitrile

C = Nickle catalyst

Method 2:

1. ​Haloalkane / RX + Ammonia → Ammonium salt w/ X halogen
2. Ammonium salt + NaOH → Primary amine + NaX + H₂O

R = NH₃, haloalkanes

C = 1. Excess ammonia is used to prevent further substitution of amine group to form secondary / tertiary amines. 2. Ethanol as solvent to prevent any substitution of the H₂O to produce alcohols

Question 19

Producing secondary / tertiary amines

Reagents + conditions

Answer 19

1. Primary amine + Haloalkane → Dialkylammoniumm salt
2. Dialkylammoniumm salt + NaOH → Secondary amine + NaX + H₂O

Tertiary amines are just a further loop of the reaction with secondary amines

Question 20

Preperation of aromatic amines

Reagents + conditions

Answer 20

Reduction of nitrobenzene gives aromatic amine:

Nitrobenzene + H₂ → Aromatic amine + H₂O

R = Tin(Sn) and conc HCl to act as a reducing agent

C = Ecess NaOH_(aq), heat under reflux

Question 21

Give the structure of an amino acid

Answer 21

Question 22

Define alpha amino acid

Answer 22

Alpha amino acid = Amine group attached to alpha carbon (2^nd carbon atom) which is next to a carboxyl group

Question 23

Amine group of amino acid + Acid → ?

Answer 23

Amine group of amino acid + Acid → Ammonium salt

Question 24

Carboxyl group + aqueous alkali → ?

Answer 24

Carboxyl group + aqueous alkali → Salt + Water

Question 25

Carboxyl group of amino acid + Alcohol group → ? Reagents + conditions

Answer 25

Esterification **Carboxyl group of amino acid + Alcohol group → Ester + Water** **R** = Amino acid, alcohol **C** = Small amounts of H₂SO₄ and one excess alcohol

Question 26

Define **isoelectric point**

Answer 26

**Isoelectric point** = Point at which the zwitterion forms

Question 27

Define **zwitterion**

Answer 27

**Zwitterion** = Point at which the amino acid has no overall charge because it contains both positively / negatively chagred groups

Question 28

Give the structure of primary, secondary and tertiary amides

Answer 28

Question 29

Define **optical isomers**

Answer 29

**Optical isomers** = 2 non-superimposable mirror images of a molecule as a result og having a chial atom

Question 30

Name the one amino acid that doesn't exhibit optical isomerism

Answer 30

Glycine

Question 31

What are a pair of enantiomers?

Answer 31

They're a pair of optical isomers

Question 32

Show that amino acids have a chiral carbon

Answer 32

Question 33

Define **addition polymer**

Answer 33

**Addition polymer** = Formation of a very long molecule chain, by repeating addition reactions of unsaturated small monomers

Question 34

Define **condensation polymer**

Answer 34

**Condensation polymer** = Formation of a very long molecule chain by the joining of monomer(s) together in which H₂O is lost

Question 35

2 ways to make polyamides = ?

Answer 35

_Method 1:_ **​Dicarboxylic acid + Diamine → polyamide + H₂O** _Method 2:_ **Molecule that contains both a carboxyl group and amine group**

Question 36

Give 2 example of polyamides used in real life + what are their uses

Answer 36

**_Nylon 6,6:_** It's very strong ∴ useful for: * making ropes, fishing nets and fabrics **_Normex:_** Synthetic heat + fire retardant polymer. Used in oven gloves and fire protective wear worn by formula 1 racing drivers and pit crew

Question 37

What does the 6,6 refer to in nylon 6,6?

Answer 37

The number of carbons present in the diamine and dicarboxylic acid

Question 38

Acid hydrolysis of polyamides Reagents + conditions + products

Answer 38

**Polyamide + H₂O ⇌ Dicarboxylic acid + Dialkylammonium salt** **R** = Dilute aqueous acid (H⁺) catalyst, H₂O **C** = Heat under reflux REVERSIBLE

Question 39

Base hydrolysis of polyamides Reagents + conditions + products

Answer 39

**Polyamide → Dicarboxylate salt + Diamine** **R** = OH^-_(aq) ions, H₂O **C** = Heat under reflux NOT REVERSIBLE