MODULE 6: Amines, Amino Acids and Polymers
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Amine:
A compound in which one or more hydrogens in an ammonia molecule (NH3) have been replaced by a carbon chain/ring
Aliphatic amine:
Nitrogen atom is bonded to at least one straight or branched carbon chain
Aromatic amine:
Nitrogen atom is attached to an aromatic ring to form a phenylamine
Primary amine:
Only one R-group attached to the nitrogen atom
Secondary amine:
Two R-groups attached to the nitrogen atom
Tertiary amine:
Three R-groups attached to the nitrogen atom
Naming primary amines:
On carbon one it is named as ‘[prefix]amine’, the prefix being the chain before (ethyl, propyl). Any other carbon, the prefix ‘amino’ is used, with the number carbon it is on
Naming secondary and tertiary amines:
When containing the same alkyl group, di and tri are used to show the number of alkyl groups attached to the nitrogen. When containing different alkyl groups, N-substituted variant is used, e.g. N-methyl, ethylamine
Amine reaction with acids:
Amines act as a base to neutralise acids, and forms an ammonium ion (e.g. ethylammonium ion), which forms a salt
Preparation of a primary amine:
• Ammonia is reacted with a haloalkane to form an ammonium ion • The ammonium ion reacts with the haloalkane to form an ammonium salt • Sodium hydroxide is used to remove the halogen from the ammonium salt, resulting in the amine, sodium halogen salt and water • Excess alcohol is used to prevent formation of an alcohol instead of an amine • Excess ammonia is used to prevent formation of a secondary or tertiary alcohol
Preparation of secondary and tertiary amines:
SECONDARY: further substitution of a halide ion onto the lone pair of electrons on the nitrogen atom, to allow for the same reaction as a primary amine TERTIARY: further reaction of a secondary amine
Preparation of aromatic amines:
• Nitrobenzene is heated under reflux with tin and hydrochloric acid to form a phenylammonium salt, phenylammonium chloride • Then reacted with excess sodium hydroxide to form a phenylamine and two moles of water
Formula of an alpha amino acid:
RCH(NH2)COOH
Reaction of the amine group of an amino acid:
The amine group is basic, so reutralises the acid to form an ammonium ion and negative ion from the previous acid
Reaction of the carboxylic group of an amino acid:
Can react with alkalis to form carboxylate salts and alcohols to form esters
Amide:
Reactions of acyl chlorides and carboxylic acids with ammonia and amines, for example: CH3COCl + NH3 –> CH3CO(NH2) + HCl
Primary amide:
One carbon bonded to the amide group
Secondary amide:
Two carbons bonded to the amide group
Tertiary amide:
Three carbons bonded to the amide group
Chirality:
When optical isomerism occurs around a chiral center- a carbon in a molecule that is bonded to at least 4 different groups
Name of optical isomers:
Enantiomers
Chirality in amino acids:
All amino acids have chirality (except glycine)
Addition polymerisation:
When alkenes form polymers
Condensation polymerisation:
When a mole of water is formed from the formation of a polymer