Introduction to Amines
Amines are organic derivatives of ammonia. Amines, like ammonia, are weak bases
(Kb = 10−4 to 10−6). This basicity is due to the unshared electron pair on the nitrogen
atom.
Amines occur widely in both plants and animals tissues .Nicotine is found in tobacco
;and cocaine is found in the south American coca bush ,Amino acids are the building
block from all protein are made and cyclic amine basis are constituents of nucleic
acid.
Classification and nomenclature of amines
Amines are classified as primary, secondary, or tertiary based upon the number of
carbon-containing groups that are attached to the nitrogen atom. Those amine
compounds that have only one group attached to the nitrogen atom are primary,
while those with two or three groups attached to the nitrogen atom are secondary
and tertiary, respectively.
Amines named
Aliphatic amines are named by naming the alkyl group or groups attached t» nitrogen, and following these
by the word -amine. More complicated ones are often named by prefixing amino- (or N-methylamino-y
N,N-diethylamino-, etc.) to the name of the parent chain. For example:
Aromatic amines—those in which nitrogen is attached directly to an aromatic ring—are generally
named as derivatives of the simplest aromatic amine, aniline. An aminotoluene is given the special name
of toluidine. For example:
Salts of amines are named by replacing –amine by ammonium (or –aniline by anilinium )
and adding the name of the anion (chloird ,nitrate,,sulfate,etc.)for example
Heterocyclic amines—compounds in which the nitrogen atom i of a ring—are also common,
and each different heterocyclic ring! its own parent name. The heterocyclic nitrogen atom
is always position.
Physical properties of amine
Like ammonia, amines are polar compounds and, except for tertiary amines, :an form
intermolecular hydrogen bonds. Amines have higher boiling points than non-polar
compounds of the same molecular weight, but lower boiling points ban alcohols or carboxylic
acids.
Amines of all three classes are capable of forming hydrogen bonds with water. Vs a result,
smaller amines are quite soluble in water, with borderline solubility being reached at
about six carbon atoms. Amines are soluble in less polar solvents like ether alcohols
,benzene.Aromatic amines are very toxic. They are readily absorbed though the skin, often
with fatal results.
Basicity of amines
Amines are basic because they possess a pair of unshared electrons, which they can
share with other atoms. These unshared electrons create an electron density around
the nitrogen atom. The greater the electron density, the more basic the molecule.
Groups that donate or supply electrons will increase the basicity of amines while
groups that decrease the electron density around the nitrogen decrease the basicity
of the molecule. For alkyl halides in the gas phase, the order of base strength is given
below:
(CH3)3 N > (CH3)2NH > CH3NH2 > NH3
However, in aqueous solutions, the order of basicity changes.
(CH3)2 NH > CH3NH2 > (CH3)3N > NH3
The differences in the basicity order in the gas phase and aqueous solutions are the
result of solvation effects. Amines in water solution exist as ammonium ions.
In water, the ammonium salts of primary and secondary amines undergo solvation
effects (due to hydrogen bonding) to a much greater degree than ammonium salts of
tertiary amines. These solvation effects increase the electron density on the amine
nitrogen to a greater degree than the inductive effect of alkyl groups.
Arylamines are weaker bases than cyclohexylamines because of resonance.
Aniline, a typical arylamine, exhibits the resonance structures shown in Figure 1 .
Preparation Of Amines
Reactions of Amines
Basicity. Salt formation.
Uses of amines
As drugs

Chlorpheniramine is an antihistamine the helps to relief allergic disorders due to cold, hay fever, itchy
skin, insect bites and stings.

Diphenhydramine is the common antihistamine, benadryl.

Chlorpromazine is a tranquillizer that sedates without inducing sleep. It is used to relieve anxiety,
excitement, restlessness or even mental disorder.

Acetaminophen is also known as paracetamol or p-acetaminophenol, an analgesic that relieves pains
such as headaches. It is believed to be less corrosive to the stomach and is an alternative to aspirin.