Download Properties of amines

Properties of amines
Amines are compounds based on an ammonia molecule
(NH3), where one or more of the hydrogen atoms is
replaced by a carbon chain.
Thus R—NH2 is a primary amine, while R—NH—R’ is a
secondary amine, and R—N(R’)—R’’ is a tertiary amine.
You will only be asked to name primary amines.
Note that 2-aminopropane, CH3—CH(NH2)—CH3, is a
primary amine, yet the haloalkane from which it was made,
CH3—CHCl—CH3, is a secondary haloalkane.
Hydrogen bonding occurs in amines, but it is not as strong
as the hydrogen bonding occurring in alcohols because the
N—H bond is not as polar as the O—H bond. So amines
have lower boiling points than the corresponding alcohols.
Low-mass amines are
miscible in water.
Like ammonia itself,
amines are bases.
Amines turn litmus paper
blue.
Amines are the only class
of organic compounds you
will meet this year which
turn litmus blue.
C3H7—NH2 + H2O
C3H7—NH3+ + OH–
Learn this equation.
The low-mass amines are gases or volatile liquids with a
noticeably fishy smell. (Actually, it is dead fish which smell
of amines as the proteins in their flesh break down.)
Like ammonia itself, amines react with inorganic acids to
form ionic salts which are soluble in water and have no
odour.
C3H7—NH2 + HCl →
propyl amine
C3H7—NH3+ Cl–
propyl ammonium chloride
A few drops of universal
indicator solution are
added to dilute
hydrochloric acid.
Ethylamine is a gas, so
this bottle contains a
solution of ethylamine in
alcohol.
Ethylamine is added dropwise until no further colour
change takes place.
C2H5—NH2 + HCl →
ethylamine
C2H5—NH3+ Cl–
ethyl ammonium chloride
Learn this equation and the product name.
We added acid dropwise until the mixture was exactly
neutral.
Amines are bases which react with acids to form salts, just
like inorganic bases do.
This pale blue ppt is copper
hydroxide
Also like ammonia, amines react with copper sulfate
solution to form a royal blue complex.
Cu2+ + 4C3H7NH2 → [Cu(C3H7NH2)4]2+