I'm Keith Haynes.
I'm a graduate student here at the University of North Texas.
Today, we're going to be doing several functional group tests.
These tests are a simple, easy way
to tell what functional groups are
present in organic molecules.
They don't actually tell us the structure
of the molecule themselves.
We'll be doing these tests and the solid and the liquid phases
to tell the difference between the two.
And we'll also be testing for phenols, alcohols, amines,
carboxylic acids, and for unsaturation.
A saturated sodium bicarbonate solution
can be used to test for carboxylic acid functional
groups.
A positive test will give off bubbles, which are actually
carbon dioxide gas.
Upon addition of hydrochloric acid,
we find that the carboxylic group falls out of solution.
But it can easily be neutralized again
by using sodium hydroxide solution.
So we are now going to do the same tests for carboxylic acids
in the liquid phase.
So now I'm going to add some sodium bicarbonate.
Upon addition of hydrochloric acid,
the group should fall out of solution.
Sodium hydroxide can be used to test for phenols.
Phenols are very weak acids, so a strong base
like sodium hydroxide must be used to deprotonate and form
the phenoxide ion.
Sodium bicarbonate is not basic enough to react with phenols.
Upon addition of sodium hydroxide,
we notice that there's a reaction as the phenoxide ion
is being formed.
Once we add hydrochloric acid, we
notice a precipitate falls out.
To test for amines, we first check
whether it is soluble in strong mineral acids,
such as concentrated hydrochloric acid.
Amines dissolve, forming a water soluble salt. When
aqueous sodium hydroxide is added to the solution,
we notice that the amine precipitates out.
Other tests can be done to determine
if the amine is primary, secondary, or tertiary.
When we add concentrated hydrochloric acid,
we notice that the amine goes in the solution
as a forms of water soluble salt.
When we add sodium hydroxide, we notice that the amine
precipitates out.
Sodium metal can be used to test for alcohols.
A small piece of freshly cut sodium
will float on the surface as it's suspended by the hydrogen
gas it releases.
The result is a formation of an alkoxide.
Bromine can be used to test for unsaturation.
Once the dilute bromine solution's added,
the solution is then decolorized.
This occurs as the bromine reacts and is
removed from the solution.
Once all the double bonds have reacted,
the bromine color will persist.