DUE DATES

1
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.
2
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

3
Report Notes Last Week

• Pay attention to significant figures in
  calculations.
• Properly labeled vial example in Pavia (page
  number was written on the blackboard). It must
  include the melting point range you always
  report ranges (and it is an indication of purity).

4
In Lab Today

• Learn the new technique of extraction
• Drying organic solvents (See p. 697 in Pavia)

5
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

6
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

Separatory funnel with stopper Aqueous layer on
top Methylene chloride layer on bottom
(contains caffeine) Drain off CH2Cl2 bottom
layer into beaker Total 3 extractions (8 ml x 3)
7
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.

8
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 ? MgSO410H2O
• When you are ready to dry your solution, bring it
  to the instructors bench.
• After drying, decant the solution into a
  pre-weighed beaker.

9
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.

10
Report for Next Week

• Report Form in Manual
• Separation scheme (flow chart of procedure for
  separating a pure product from reaction
  by-products 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)

11
Report for Next Week

• Some additives in Vivarin
• polyethylene glycol and polysorbate 80
  (water-soluble)
• titanium dioxide and silicon dioxide
  (water-insoluble)
• DC yellow 10 and yellow 6 aluminum lake
  (water-insoluble)
• carnauba wax (water-insoluble)

12
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.)

13
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

14
Weekly Clean-up

• Harbour and Tohti