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Gas Chromatography-Mass Spectrometry
ChemDraw
Tests for Halides
Silver Nitrate in Ethanol Test
Silver Nitrate in Ethanol Test
Standards,
as done in the Classification Tests for Halides lab
|
1-chlorobutane |
1-bromobutane |
1-iodobutane |
|
2-chlorobutane |
2-bromobutane |
2-iodobutane |
|
2-chloro-2-methylpropane |
2-bromo-2-methylpropane |
|
|
benzyl
chloride |
bromobenzene |
Procedure
Place approximately 0.25 mL of each compound into a test tube.
Add 2 mL of a 1% ethanolic silver nitrate solution to the material
in
each test tube, noting the time of addition. After the addition, shake
the test tube well to ensure adequate mixing of the compound and
the solution.
Record the time required for any precipitates to form. If no precipitates
are seen after 5 minutes, heat the solution on the steam bath for
approximately
5 minutes. Note whether a precipitate forms in the test tube. Continue
slow reactions for up to 45 minutes at room temperature.
Complications
Carboxylic acids have been known to react in this test, giving false positives.
Standards
Reference tests done in Classification Tests for Halides Lab
Procedure
In a test tube place 0.25 mL or 0.2 g of your unknown. Add 2 mL of a 15%
solution of sodium iodide in acetone, noting the time of addition.
After
the addition, shake the test tube well to ensure adequate mixing of the
unknown and the solution. Record the time needed for any precipitate
to
form. After about 5 minutes, if no precipitate forms, place the test
tube in a 50oC water bath. Be careful not to allow the
temperature of the water bath to go above this temperature since
the acetone will
evaporate, giving a false positive result. After 6 minutes more in the
bath, if no precipitates are visible, remove the test tube and let
it
cool to room temperature. Note any change that might indicate that a
reaction has occurred. Continue slow reactions for up to 45 minutes
at room temperature.
Positive
Test
The formation of a white precipitate indicates the presence of halides.
Complications
When the sodium iodide solution is added to the unknown, a precipitate of sodium
iodide might occur leading to a false positive test. Upon mixing, the precipitate
of sodium iodide should dissolve.
Standards
Any halogenated compound as a positive standard, such as, 1-Bromobutane,
and any non-halogenated compound, such as 1-Butanol, as a negative standard.
Procedure
Heat the tip of a copper wire in a burner flame until there
is no further coloration of the flame. Let the wire cool slightly, then
dip it into the unknown (solid or liquid and again, heat it in
the flame. A green flash is indicative of chlorine, bromine, and iodine;
fluorine is not detected because copper fluoride is not volatile. The
Beilstein test is very sensitive, thus halogen-containing impurities
may give misleading results.
Positive
Test
A green flash is indicative of chlorine, bromine, and iodine, but NOT fluorine.