Organic Chemistry Lab 315
Fall, 2014
Note that the reading for this experiment is
Technique 12. The experiment (Extraction of
Caffeine) is in the Manual.
DUE DATES
• Today
– At beginning of lab – Identification of an Unknown
Report
– Problem #1, Part II, Spectroscopy Problem Set
– At end of lab -- copy of laboratory notebook pages
for today's experiment (do not turn in your pre-lab
notes or in-class notes)
• Next Week
– Part II, #2 Spectroscopy Problem Set
– Extraction of Caffeine Report
In Lab Today
• Learn the new technique of extraction
• Drying organic solvents (See p. 697 in
Pavia)
Experiment Notes
Beaker containing
dissolved caffeine
and insoluble binder
Funnel with glass
wool as filter
Separatory funnel
supported on iron
ring on ring stand
Stopcock closed
Beaker underneath
“just in case”
Experiment Notes
Beaker containing
dissolved caffeine
and insoluble binder
Separatory funnel
with stopper
Funnel with glass
wool as filter
Aqueous layer on
top
Separatory funnel
supported on iron
ring on ring stand
Methylene chloride
layer on bottom
(contains caffeine)
Stopcock closed
Beaker underneath
“just in case”
Drain off CH2Cl2
bottom layer into
beaker
Total 3 extractions
(8 ml x 3)
Experiment Notes
Extractions in a Separatory funnel
•Add liquids using a glass funnel in order to not
contaminate the neck of the sep. funnel.
•After replacing the stopper, turn the sep. funnel
upside down to vent. Repeat if audible gas escapes.
•Shake/swirl gently, but thoroughly, to mix the
immiscible liquid phases. Emulsion may form in this
experiment.
•Caffeine is in the bottom CH2Cl2 layer. Drain bottom
layer through stopcock into 100 ml beaker. [This is
one extraction.]
•Add additional CH2Cl2 (using glass funnel) from top.
•Extract with CH2Cl2 three times total, combining all
extracts in beaker.
Experiment Notes
There will be water dissolved in the CH2Cl2 extracts that
needs to be removed.
Organic solvents are “dried” by using an anhydrous salt that
can absorb the water and become hydrated.
See Section 12.9 in Pavia for common drying agents and
equations for anhydrous salt → hydrated salt
MgSO4 + H2O → MgSO4∙10H2O
When you are ready to dry your solution, bring it to the
instructor’s bench.
After drying, decant the solution into a pre-weighed beaker.
Experiment Notes
• Make sure the balance is displaying ±.001g
• Evaporate solvent using a hot plate UNDER THE
HOOD.
• Do not recrystallize caffeine.
• Weigh the beaker and mostly dry caffeine.
• Place your caffeine in a properly labeled vial. See Pavia
for an example of a correctly labeled vial.
• Caffeine tablet contains 200 mg of caffeine. The
remainder is “inert ingredients”.
• Calculate the % isolation based on the mg caffeine in the
2 tablets.
Report for Next Week
• Report Form in Manual
• Separation scheme (flow chart of procedure for
separating a pure product from reaction byproducts or mixture impurities)
– See explanation and example in Manual/class web
page
• There is no written report required (major
grading will be for the Separation Scheme – be
sure you understand it)
Report for Next Week
• Some additives in Vivarin:
– polyethylene glycol and polysorbate 80
(water-soluble)
– titanium dioxide and silicon dioxide (waterinsoluble)
– D&C yellow #10 and yellow #6 aluminum lake
(water-insoluble)
– carnauba wax (water-insoluble)
Report for Next Week
• These additives should be included in your
Separation Scheme for isolating caffeine from
Vivarin tablets. You do not need to find the
structures for these compounds.
• You can ignore the effect of Na2CO3 on the
water-solubility of any of these additives,
although it should be included in the scheme.
(Na2CO3 was added to the Vivarin-water
solution.)
Report for Next Week
• Your Separation Scheme should resemble
the one done for isolation of caffeine from
tea leaves, shown in class.
• Tea leaves separation
Right-click on the hyperlink above, and then
choose “open hyperlink”’
Weekly Clean-up
• Harbour and Tohti