Lab 7

 Alkaloid
 Purine Ring System
 Stimulant (50 – 200 mg)
 Diuretic
 Found in natural sources
 Coffee
 Tea
 Kola nuts
 Cocoa beans
 Caffeine
 5% by weight
 Soluble in hot water
 Tannins
 High MW phenolic
 Soluble in water
 Cellulose
 Insoluble in water
 Other substances
 Chlorophyll, etc…
Isolation Procedure
Tea Leaves
Hot water
Caffeine in CH2Cl2
Insoluble Cellular Material
Tannin Salts in Water
Isolation Procedure
Open two tea bags and weigh contents to the nearest 0.0001g.
• Record weight.
• Put tea into one bag, close, and staple.
Isolation Procedure
 Add …
 50 mL of distilled water
(not 30 mL)
 2.0 g anhydrous Na2CO3
 Heat (gentle boil) for 20 min
 Cover with watch glass
and hold down, if
necessary, with glass rod.
Isolation Procedure
• Decant the hot liquid into a
50mL beaker (not
erlenmeyer flask)
Wash with 10 mL hot
water (instructor has hot
Add wash water to extract
Cool to room temperature!!
Discard tea bags in waste
Isolation Procedure
 Transfer the tea extract
to a separatory funnel
on a ring clamp
Isolation Procedure
Carefully add 5.0 mL of dichloromethane (DCM) to the separatory funnel.
• Follow the procedure in the lab manual CAREFULLY (pg. 89 step 5).
Your instructor will now demonstrate the proper extraction procedure using the
separatory funnel!
Isolation Procedure
 You MUST be individually
checked off by your instructor
(after pre-lab lecture) before you
can complete this step during
Isolation Procedure
 Make sure …
 the stopper is held tightly and no
liquid spills
 The liquid is not in contact with
the stopcock when you…
 …open the stopcock to release
built up pressure caused by gas
 Then close the stopcock and
gently mix by inverting funnel.
 Release the pressure as before!
 Gently mix and vent 2 – 3 times
Isolation Procedure
 Return separatory funnel
to the ring clamp
 REMOVE the stopper
 Two distinct layers will
form after a few minutes
What is in the top layer?
The bottom layer??
Isolation Procedure
 CAREFULLY drain the
lower layer into a 25mL
erlenmeyer flask
 Try not to get any water
into the flask!
Isolation Procedure
 Repeat the entire
extraction procedure
with an additional 5 mL
then …
 Combine the separated
bottom layer with the
DCM layer obtained
Isolation Procedure
 Add 0.5 g anhydrous
Na2SO4 to remove excess
 No swirling necessary!
Isolation Procedure
 Weigh a small beaker
(30mL) or separatory
funnel containing 1 – 2
new boiling stones!
 By means of gravity
filtration, filter the DCM
– salt mixture
 Rinse with an additional
2 ml DCM
Isolation Procedure
 Remove the DCM by evaporation in the hood
Use a hot water bath
Monitor carefully – do not leave your hood!
Be careful not to overheat!
DCM is toxic – do not breathe fumes
 While the DCM is evaporating, clean up your station
 Follow lab procedure to calculate percent yield!
Melting Point Determination
 Dispose of all waste in
hazardous waste
 Then… your instructor
will show you how to
determine the m.p. of
your caffeine! 
 Dichloromethame
 Toxic and must be carefully handled
 It evaporates quickly – do not get excess!
 Do not waste!!
 You must be checked off on the separatory funnel
procedure prior to the extraction step
Potential Health
 Inhalation: irritant, allergen, coughing, drowsiness, damage to the lungs,
shortness of breath, labored breathing, loss of appetite and delayed lung
 Ingestion: corrosive, burning, headaches, gastritis, intoxication, blindness,
pain of the mouth and stomach, anorexia, thirst, diarrhea, dizziness,
nausea, vomiting, irritability, confusion, low blood pressure, tachycardia,
tachypnia, mental disturbances, skin discoloration, circulatory collapse,
clammy skin, weak pulse, shallow respirations, coma and death
 Skin contact: irritant, delayed burns, redness, cracking, flaking, dermatitis,
defatting of the skin, absorption through the skin and white and wrinkled
skin later
 Eye contact: irritant, corrosion of the eyes with burns, tearing, redness,
pain, blurred vision, permanent damage and blindness
 Tumorigen, mutagen, teratogen and reproductive effector
Finally …
 This was the last lab!  
 Next week - Be prepared for the cumulative written
Lab coat
Eat before class!
Wear yellow! 

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