Chapter 6: Liquid/Liquid Extraction

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Lecture 7

• Chapter 6 Liquid/Liquid Extraction
• NMR Chemical Shift, Equivalent Hs
• This week in lab
• Ch 5 Distillation Boiling Point, Procedure 3
• For the final report, remember to correct boiling
  points for the
• pressure!
• Next week in lab
• Ch 6 Procedure 1 PreLab Due Quiz 3
• Due Chapter 4 Final Report. Please do question
  9 INSTEAD OF question 8!!

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Chapter 6 Liquid/Liquid Extraction

• Extraction
• Pulling out a component from a mixture
• Used to isolated specific compounds
• Used to purify a compound
• Types Liquid/liquid extraction, solid/liquid
  extraction
• Two day lab
• Procedure 1 Separation of an unknown
  three-component mixture
• Procedure 2 Extraction of caffeine from tea

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Chapter 6 Procedure 1

• Separation of an unknown three-component mixture
• Acidic component (CO2H)
• Basic component (NH2)
• Neutral component

Possible Unknowns
Separate by acid/base chemistry
Once separated, take a m.p. of each to determine
the identity.
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Chapter 6 Procedure 1

• Example Separate these three components

Use a flow chart to visualize how the separation
will work
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Chapter 6 Procedure 1

• Once the separation is complete
• Dry each, weigh and calculate recoveries
  (assume you started with equal amounts of each)
• Take a m.p. of each to determine identities
• Change in Lab Guide Either take an IR of
  the acidic component OR an NMR of the neutral
  component

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Chapter 6 Procedure 2

• Extraction of caffeine from tea
• Steep tea bags in hot water
• Extract aqueous solution with dichloromethane
  (CH2Cl2) to
• isolate caffeine

For extraction, use a separatory funnel Get a
demo from your TA. A few, smaller extractions
are better than one big extraction.
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Chapter 6 Procedure 2

• Once caffeine has been isolated, purify via
• sublimation.
• Weigh the isolated caffeine and calculate the
  amount of caffeine per gram of tea leaves.

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Nuclear Magnetic Resonance

• Information Gained
• Different chemical environments of nuclei being
  analyzed (1H nuclei) chemical shift
• The number of nuclei with different chemical
  environments number of signals in spectrum -
  look for symmetry!
• The numbers of protons with the same chemical
  environment integration
• Determine how many protons are bonded to the same
  carbon integration
• Determine the number of protons that are adjacent
  to one another splitting patterns
• Determine which protons are adjacent to one
  another coupling constants

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Chemical Shifts

• Shielded protons appear more upfield (lower ppm
  value).
• Deshielded protons appear more downfield (higher
  ppm value).

Correlation Chart
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Equivalent Non-Equivalent Hydrogens
Consider the following molecules. Determine
which protons are equivalent and non-equivalent.
Predict the number of signals that would appear
in the 1H NMR spectra of these compounds. Look
for symmetry!