2. Definition
Simple & Fractional Distillation: distillation of two miscible liquids.
Raoult’s Law: PT = x1P1° + x2P2°
Codistillation: distillation of two immiscible liquids.
Dalton’s Law: PT = P1º + P2º
Compounds 1 and 2 start to codistill when PT is equal to atmospheric
pressure (760 torr).
Steam Distillation: distillation of water + another liquid.
Pure Water: Pwº = 760 torr at 100 ºC
Advantage: steam distillation allows the mixture of organic liquids to distill
below 100 ºC: good for unstable or high boiling point compounds.
3. Essential Oils
A volatile oil, usually having the characteristic odor or flavor of the plant, frequently is a
water-immiscible liquid separated by distillation from the plant material. Such oils are
used to make perfumes, flavorings, cosmetics, incenses, and medicine.
For example: Clove oil consists of several compounds such as eugenol,
example
which is the major component (85-90%) and eugenol acetate (9-10%).
Eugenol has a boiling temperature of 254 ºC and can be steam distillated
from freshly ground clove.
4. Steam Distillation Set-Up (Semi-Microscale)
stopper instead of thermometer
fill with H2O
rubber
claisen bands
adapter
125 mL E.
flask
mark level
with marker
500 mL flask with boiling chip Heating mantle supported with lab jack
5. Changes from the Lab Manual
1. Use 10 grams of powdered cloves/150 mL of water rather than 5
grams of whole cloves/40 mL of water.
2. Use a 500 mL round bottom flask rather than a 100 mL round
bottom flask.
3. Collect 100 mL distillate in a 125 mL E. flask.
4. Use a heating mantle for your heat source rather than a bunsen
burner or a hot plate.
5. Use ether to extract the distillate rather than methylene chloride.
6. Clove Powder in the Flask
Adding Cloves into the round bottom Formation of big bubbles during
flask using the stemless funnel the distillation will be seen.
Powdered cloves may lead to
foaming if too much heat is
applied.
7. Experimental Procedure
Steam Distillation:
• Don't forget to apply grease at every glass joint.
• Distill at a steady rate: 1 drop/2-3 seconds (instead of 1 drop/5 seconds).
• Maintain water level by adding water from the addition funnel to the marked
level.
• Distill until no oily layer is apparent. Collect at least 100 mL of distillate
(water + clove oil).
Extraction: to separate clove oil from water
• Transfer distillate to a separatory (sep) funnel and add 10 mL of saturated
NaCl solution to the sep funnel.
• Rinse condenser and receiving flask with 5 mL of ether and transfer this to
the sep funnel.
ether layer
• Swirl gently and vent the sep funnel.
aqueous layer
• THEN, vigorously shake with
frequent venting.
8. Let the layers separate. Drain the aqueous layer (bottom layer). Transfer the
ether layer (top layer) to a 50 mL E. flask.
Return the aqueous layer to the sep funnel. Extract two more times with 5 mL
portions of ether (each time rinse the receiving flask and the condenser
before adding to the sep funnel).
Dry the combined ether extracts over anhydrous Na2SO4 for 5 min. Decant as
much as possible before removing the rest with a pipet.
Filter the ether solution through a cotton plugged pipet into a preweighed
50-mL round bottom flask
Rinse the Na2SO4 with three additional 2-mL portions of ether and filter into
the preweighed 50-mL round bottom flask.
Rotary Evaporation: Remove ether from your oil by rotary evaporation.
Remove the last traces of ether with the house vacuum. Let it dry for one week.
9. Final Notes
- Determine % recovery of eugenol.
DO NOT dissolve eugenol in methanol!!!!
- Next week - converting eugenol to the ester derivative (get handout in your lab)
Omit : 1. TLC
2. The qualitative tests described in the module.
Waste: - One bottle is in the hood for ether / water waste.
Waste
- DO NOT collect cloves! Decant water from the reaction flask
into the sink, put cloves in a paper towl and throw in the trash.
Don't forget: You will also weigh, perform TLC, and measure the melting point for
each of your compounds from last week. You need to submit your samples in marked
vials as instructed by your TA. You must turn in your TLC plates with your lab report in
an envelope or zip lock bag.
