Chapter 9
Nitrogenous compounds
A) AMINES
B) AMIDES
AMINES
• Amines are carbon – hydrogen – nitrogen compounds
• An Amine is an organic derivative of ammonia (NH4) in which one or
more alkyl, cycloalkyl, or aryl groups are attached to the nitrogen
atom.
• The general formula for amines is R – NH2
Nomenclature of amines
• Count the carbons in the longest chain containing the amine
• Drop the –e ending for the parent name and add –amine
• For a secondary amine an N prefixes the compound giving the shorter carbon chain its side chain
prefix name
• For a tertiary amine an N,N prefixes the compound giving the two shorter carbon chains their side
chain prefix names
• Aromatic amines belong to specific families, which act as parent molecules.
• For example, an amino group (—NH2) attached to benzene produces the parent compound aniline.
• The prefix ‘amino’ is used to indicate the presence of an –NH2 group
in a molecule containing more than one functional group.
Classification of Amines
• Amines are classified as primary (10), secondary (20), or tertiary (30) on the basis of how many hydrocarbon groups
are bonded to the ammonia nitrogen atom.
• Primary Amine is an amine in which the nitrogen atom is bonded to one hydrocarbon group and two hydrogen
atoms. The generalized formula for a primary amine is RNH2. e.g. CH3 – NH2 .
• Secondary Amine is an amine in which the nitrogen atom is bonded to two hydrocarbon groups and one hydrogen
atom. The generalized formula for a secondary amine is R2NH. e.g. CH3 – NH – CH3
• Tertiary Amine is an amine in which the nitrogen atom is bonded to three hydrocarbon groups and no hydrogen
atom. The generalized formula for a tertiary amine is R3N. e.g.
• .
Classify Amines each of the following Amines as a Primary,
Secondary, or Tertiary
CH3 – N – CH3
CH3
CH3 – NH
Preparation of amines
• Reduction of halides with ammonia
The reaction of ammonia with an alkyl halide leads to the formation
of a primary amine.
• The Hofmann Degradation:
It is a reaction between an amide and a mixture of bromine and
sodium hydroxide solution. -CO- part of the amide group is lost and
we get a primary amine with one less carbon atom than the original
amide had.
Physical Properties of Amines
• The methylamines (mono-, di-, tri-) and ethylamine are gases at room temperature and have
ammonia-like odors. Most other amines are liquid, and many have odor resembling that of raw
fish.
• The simples amines are irritating to the skin, eyes, and mucous membranes and are toxic by
ingestion.
• Many amines are readily absorbed through the skin and affect both the blood and the nervous
system.
• The boiling points of amines are intermediate between those of alkanes and alcohols of similar
molecular mass.
• Amines with fewer than six carbon atoms are infinitely soluble in water.
Chemical Properties of amines
(reaction of amines)
• Formation of amides
Amines react with carboxylic acids to form amides.
• Amine alkylation: (formation of quarternary salts)
Reaction of amines and acid will give amine salt (an ammonium ion).
•
CH3CH2CH2 NH2
n-propylamine
HCl
CH3CH2CH2 NH3Cl
n-propylammonium chloride
Heterocyclic Amines
• Heterocyclic amine is an organic compound in which nitrogen atoms
of amine group are part of either an aromatic or a nonaromatic ring
system.
Pyramidine
Pyridine
Pyrolidine
Uses
• Primary aromatic amines are used as a starting material for the
manufacture of azo dyes which are highly coloured, they are widely
used in dyeing industries.
• Amines are used to make many drugs which are helpful in treating
many allergies, mental disorders and insect bites etc.
• Amines are widely used industrially for removing carbon dioxide
(CO2) and hydrogen sulfide (H2S) from natural gas and refinery
process streams.