CHEM 233: Organic
Laboratory I Prelab Lecture
University of Illinois
at Chicago
UIC
O
H
(R)-Carvone
Lab 5: Steam Distillation of Monoterpenes Carvone and
Limonene from Caraway Seeds. Analysis of Products by
Infrared Spectroscopy and TLC.
O
H
(S)-Carvone
Midterm Exam Reminder
Midterm Exam =
_
• Sample exam online: www.chadlandrie.com (shared files page).
• Review past homework questions & assigned reading.
• Review background info provided in course manual.
• Review prelab lecture notes.
• Exam will be given during your lab time in the same room.
• Topics cover both theory and techniques of lab experiments.
University of
Illinois at Chicago
UIC
© 2009, Dr. Chad L. Landrie
CHEM 233: Organic Chemistry Laboratory 1
Slide 2
Prelab Lecture: Lab 5
Steam Distillation: Applications & Goals
Applications:
Today’s Goals:
1. Last separation/
purification technique in part
one of CHEM 233 course.
1. Isolate carvone from
caraway seeds by steam dist.
Determine enantiomer.
2. Industrial = isolation of
volatile essential oils from
plant material.
2. Obtain IR of isolated oil;
compare to known IRs of
carvone.
3. General = isolation of
oils/liquids with high bps.
3. Obtain TLC of isolated oil
with a co-spot of authentic.
University of
Illinois at Chicago
UIC
© 2009, Dr. Chad L. Landrie
CHEM 233: Organic Chemistry Laboratory 1
Slide 3
Prelab Lecture: Lab 5
Steam Distillation: Advantages & Requirements
Advantages:
Requirements:
1. Distill liquids with high
boiling points at
temperatures < 100ºC.
1. Non-reactive with H2O.
2. Avoid high temp simple/
fractional distillation, which
could cause decomposition.
3. Stable (does not
decompose) at 100 ºC.
2. Immiscible with H2O.
4. Pº ≥ 5 Torr at 100 ºC.
3. Alternative = vacuum dist.
University of
Illinois at Chicago
UIC
© 2009, Dr. Chad L. Landrie
CHEM 233: Organic Chemistry Laboratory 1
Slide 4
Prelab Lecture: Lab 5
Steam Distillation Apparatus
separatory
funnel
(used here as
a dropping funnel)
Notes:
1. No need for boiling stones; caraway seeds
provide sufficient sites for nucleation.
2. Steam is generated in situ by boiling water in
the stillpot.
3. Replacement water (hot) is added at the
same rate distillate is exiting the condenser.
replacement
water
(hot!!)
stillhead
Claisen
adapter
water &
caraway seeds
University of
Illinois at Chicago
UIC
4. Separatory funnel is actually being used
during the distillation as a dropping funnel.
5. Collect approximately 75 mL of distillate.
Distillate will be cloudy since carvone and water
are immiscible.
6. Volatile components in the caraway seeds are
co-distilling with the water vapor.
© 2009, Dr. Chad L. Landrie
CHEM 233: Organic Chemistry Laboratory 1
Slide 5
Prelab Lecture: Lab 5
Initial Considerations
O
O
H
H
(R)-Carvone
O
H
H
(S)-Carvone
water
1. Which compound above has the highest Pº? Lowest?
2. In a mixture of water and carvone, which would you
expect to distill out first? Why?
3. Do you expect carvone to be soluble in water? Why or
why not?
University of
Illinois at Chicago
UIC
© 2009, Dr. Chad L. Landrie
CHEM 233: Organic Chemistry Laboratory 1
Slide 6
Prelab Lecture: Lab 5
Principles: Mathematical
immiscible = not soluble in all proportions
For immiscible component (x) in a
heterogeneous mixture with H2O:
Raoult’s Law: Px = Nx * Pxº
Dalton’s law still applies:
PT = Pxº + PH2Oº
or
PT = Px + PH2O
bp (mixture): PT = Patm
Px = Pxº
Since x is not soluble in water, it does not depend on its
mole fraction in the mixture. This relationship applies to each
component in mixture, including water.
University of
Illinois at Chicago
UIC
Conclusion:
The total vapor pressure (PT) is always
higher than the most volatile component-always H2O in steam distillation.
The bp of the mixture is always lower than
the lowest boiling component--again,
always H2O (100ºC) in steam distillation.
© 2009, Dr. Chad L. Landrie
CHEM 233: Organic Chemistry Laboratory 1
Slide 7
Prelab Lecture: Lab 5
Principles: Graphical
Vapor Pressure-Temperature Diagram for Water, Carvone and Limonene
900
atmospheric pressure
800
760
Pressure (Torr)
700
O
PT
PH2O
600
500
400
300
200
Plim
Plim
100
0
0
50
100
150
Temperature
200
250
(0C)
boiling point (< 100 ºC): PT = (PH2O + Plim + Pcar) = 760 Torr
University of
Illinois at Chicago
UIC
© 2009, Dr. Chad L. Landrie
CHEM 233: Organic Chemistry Laboratory 1
Slide 8
Prelab Lecture: Lab 5
Procedure Notes on Extraction
• Your TA will demonstrate
proper use of a separatory
funnel for extractions.
H2O layer
(d = 1.0 g/mL)
CH2Cl2 layer
(d = 1.33 g/mL)
• CH2Cl2 and water are
immiscible.
• Less dense liquid (H2O in
this case) is top layer.
• Like dissolves like;
therefore, carvone (organic)
is soluble in CH2Cl2
(organic).
University of
Illinois at Chicago
UIC
© 2009, Dr. Chad L. Landrie
CHEM 233: Organic Chemistry Laboratory 1
Slide 9
Prelab Lecture: Lab 5
Analysis of Isolated Oil
Thin-Layer Chromatography
Infrared Spectroscopy
• Compare Rf value of isolated oil with
authentic sample of carvone.
• Find a solvent system (mixture of EtOAc &
hexanes) where Rf < 0.6.
• Use a co-spot.
• Are the Rf values of the isolated and
authentic samples of carvone the same or
different? What does the result imply?
• Is the oil mainly one component or a
mixture of many components?
• Obtain IR of isolated oil. You may need
volatiles cover since carvone is, well, volatile.
isolated oil
(dilute in small
amount of CH2Cl2)
University of
Illinois at Chicago
co-spot
UIC
authentic sample
of carvone
• Compare your IR spectra with those of
carvone on next slides.
• Identify singnals for C=C, C=O in your
spectra.
Smell!!
Does your oil smell like spearmint [(R)-carvone]
or does it smell like caraway [(S)-carvone]?
Consult with your friends; maybe the receptors
in your nose can’t tell the difference!! IR and
TLC cannot tell you which enantiomer of
carvone you’ve isolated--only your nose. Optical
rotation can differentiate between enantiomers,
but we do not have a polarimeter.
© 2009, Dr. Chad L. Landrie
CHEM 233: Organic Chemistry Laboratory 1
Slide 10
Prelab Lecture: Lab 5
IR of Both Enantiomers of Carvone
(S)-(+)-Carvone
(S)-carvone is the
enantiomer of (R)-carvone
Enantiomers have the
same physical properities
including IR vibrational
frequencies, mp, bp, Rf, etc.
(R)-(-)-Carvone
IR spectra for both
enantiomers of carvone-and for any two
enantiomeric
compounds--are identical.
University of
Illinois at Chicago
UIC
© 2009, Dr. Chad L. Landrie
CHEM 233: Organic Chemistry Laboratory 1
Slide 11
Prelab Lecture: Lab 5