Lecture 3
Chapter 5: Extraction
Lecture Problem 1 Due Thursday
This week in lab:
Ch 4: Recrystallization & Melting Point
Procedures 1 & 2
Ch 4 PreLab Due
Quiz 1
Next week in lab:
• Ch 4: Procedures 3 & 5
• Ch 5: Extraction, Procedure 1
• Ch 5 PreLab Due & Quiz 2
Chapter 5: 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 or coffee
Chapter 5: Procedure 1
Separation of an unknown three-component mixture:
• Acidic component (CO2H)
• Basic component (NH2)
• Neutral component
Possible Unknowns:
O
H3C
OH
Acids:
Separate by
acid/base chemistry
O
OH
m.p. 121°C
m.p. 109°C
O
O
Bases:
CH3
H2N
CH3
H2N
m.p. 106°C
Once separated and dry, take a m.p. of
each to determine the identity.
Take melting points the following
week.
Neutrals:
OCH3
m.p. 97°C
O
OCH3
m.p. 57°C
m.p. 80-83°C
Chapter 5: Procedure 1
Example: Separate these three components
OCH3
O
O
CH3
OH
H2N
m.p. 121°C
m.p. 106°C
OCH3
m.p. 57°C
1. Use a flow chart to visualize
how the separation will work.
2. See photos/video.
Chapter 5: Procedure 1
Once the separation is complete:
1. Dry each, weigh and calculate % recoveries (assume you
started with equal amounts of each)
2. Take a m.p. of each to determine identities
3. Either take an IR of the acidic component OR an NMR of the
neutral component
OCH3
O
O
CH3
OH
H2N
m.p. 121°C
m.p. 106°C
OCH3
m.p. 57°C
Chapter 5: Procedure 2
Extraction of caffeine:
1.
2.
3.
4.
5.
6.
Use tea bags (odd # desks) or coffee bags (even # desks)
Steep tea or coffee bags in hot water
Extract aqueous solution with dichloromethane (CH2Cl2) to
isolate caffeine
Purify caffeine by sublimation
Weigh caffeine.
Compare caffeine content in tea and coffee with
hoodmate’s data; reference data.
O
H3C
O
CH3
N
N
N
CH3
N
caffeine
Chapter 5: Procedure 2
O
Extraction of caffeine:
H3C
O
For extraction, use a separatory funnel;
Get a demo from your TA.
*A few, smaller extractions are better
than one big extraction.*
Vent funnel while shaking.
CH3
N
N
N
N
CH3
Aqueous Layer
Or ganic Layer
Aqueous layer: tea/coffee solution
Organic layer: dichloromethane/caffeine
Separatory funnel
Chapter 5: Procedure 2
Extraction of caffeine:
Vent funnel while shaking.
Point away from face,
towards back of hood.
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Chapter 5: Procedure 2
Once caffeine has been isolated, purify via
sublimation (heat solid  gas  pure solid).
Weigh the isolated caffeine and calculate the amount of caffeine per
gram of tea or coffee.
Compare data with hoodmate; reference the data.
O
H3C
O
CH3
N
N
N
CH3
N