Something fishy about amines:

3 H atoms 1 H atom replaced: 1 attached C to N 2 H atoms replaced: 2 attached C's to N 3 H atom replaced: 3 attached C's to N
Ammonia, NH3 Primary amine Secondary amine Tertiary amine
Treats drowsiness and fatigue syndrome Decongestant 'Fight or flight' to cope with sudden stress

Naming amines:

  • Start with the longest alkyl chain - propylamine
  • The shorter alkyl group is prefixed with 'N' - N - methyl propylamine
  • The prefix 'N' tells you that the alkyl group comes off the nitrogen atom.
  • A tertiary amine would have 2 prefixes of 'N' - N,N - methyl ethyl butylamine (for example)


Basicity in amines:




The inductive effect:

pH 8


pH 10



pH 12



Alkyl groups have a positive inductive effect.  This means that they give a small push of electrons towards the neighboring atom (the nitrogen).  This gives an increased electrons charge density meaning a better chance of the lone pair being used to accept a proton – Stronger base

Ammonia has no inductive effect as there is nothing attached to the functional group.

Benzene rings have a negative inductive effect. This means that the benzene ring has a small pull of electrons away from the neighboring atom (the nitrogen).  This gives a lower electron charge density making it harder for the lone pair of electrons to be used to accept a proton – Weaker base


This would be further compounded by the lone pair of electrons on the nitrogen being able to delocalize into the benzene ring.


Base reactions of amines:



Base + Acid ŕ Salt


NH3(aq) + HCl(aq) ŕ NH4+Cl-(aq) 


C4H9NH2(aq) + HCl(aq) ŕ C4H9NH3+Cl-(aq)


C6H5NH2(aq) + HCl(aq) ŕ C6H5NH3+Cl-(aq)

Questions   1 - 2  P37


Amines and their reactions


Preparation of primary aliphatic amines:

             CH3CH2CH2Cl       +       NH3      ŕ         CH3CH2CH2NH2       +       HCl

             NH3                  +       HCl      ŕ         NH4Cl



Preparation of secondary / tertiary aliphatic amines:

             CH3CH2CH2Cl       +       CH3CH2CH2NH2      ŕ         (CH3CH2CH2)2NH       +       HCl

             CH3CH2CH2Cl       +       (CH3CH2CH2)2NH      ŕ         (CH3CH2CH2)3N       +       HCl

Preparation of aromatic amines:

Synthesis of dyes from phenylamine:

        1)  Diazotisation

        2)  Coupling reactions


1)  Diazotisation:

a)  Making Nitrous acid:

NaNO2                  +             HCl                  ŕ  HNO2


         Sodium nitrite           Hydrochloric acid                 Nitrous acid             


b)  Diazotisation reaction:


2)  Coupling reaction:




Questions  1 - 3  P39    Qu 9 P41   Qu 2a (ii) (iii)  P42    Qu 11-13  P44,45


Amino acids






Zwitterion and the isoelectric point:

  • A proton is transferred from the COOH to the NH2
  • The zwitterion has no overall charge as the COO- cancels out the NH3+
  • The isoelectric point is the pH at which there is no 'net' electric charge.
  • This + / - charge increases the intermolecular forces between amino acids considerably. 
  • They are often described as having unusually high melting points.
  • You may expect this to be pH7. In actual fact is is usually around the pH6 region.
  • This is due to the fact that the COOH is actually slightly more acidic than the NH2 is basic.
  • The rest of the molecule also has an influence on how acidic and how basic the COOH and NH2 are which means that every amino acid will have a slightly different isoelectric point.

Comparison of melting points:


Melting point




Propanoic acid





Acid and base properties of amino acids:

            Acids:  Due to the basic NH2 present.

            Alkalis:  Due to the acidic COOH present.


pH < Isoelectric point: pH > Isoelectric point:
  • pH < Isoelectric point:
  • In acidic conditions there is an abundance of H+ions.
  • The amino acid acts as a base and accepts as many H+ions as possible.
  • pH > Isoelectric point:
  • In Alkaline conditions there is a defficit of H+ions.
  • The amino acid acts as an acid and donates as many H+ions as possible.


Qu 1 - 3  P51


Polypeptides and proteins


Amino acids and condensation reactions:

Forming polypeptides and proteins:

Hydrolysis of polypeptides and proteins:

Acid hydrolysis:

Alkali hydrolysis:

Qu  1 - 3  P51


Condensation polymerisation:  1)  Polyesters



1)  polyesters:

a)    2 monomers:  Diol and Dicarboxylic acids-


b)    1 monomer:  Hydroxycarboxylic acid


Qu 1-3   P55

Condensation polymerisation:  2)  Polyamides


a)    2 monomers:  Diamine and Dicarboxylic acids-


b)    1 monomer:  Hydroxycarboxylic acid

Qu 1-3   P57

Addition and condensation polymerisation

Addition polymers:

Condensation polymerisation:

Comparison of addition and condensation polymers:

  Addition polymerisation Condensation polymerisation
    Polyester Polyamide
Functional groups C=C COOH  /  OH COOH / NH2
No monomers 1 1 or 2 1 or 2
Products poly(alkene) polyester + water polyamide + water
linkage C-C

Workes example  P59

Qu  1,2  P59

Breaking down condensation polymers

1)  Hydrolysis of polyesters:

2)  Hydrolysis of polyamides:

Degradable polymers:

Photodegradable polymers:

Qu  1-3  P61


Qu 9 P41   Qu 2a (ii) (iii)  P42    Qu 11-13  P44,45


Qu  1,2,4,5,6  P 69   /   Qu 1a,2,3,4,5,6,9,10,11,12   P70-73