Caffeine Alkaloid Purine Ring System Stimulant (50 – 200 mg) Diuretic
Caffeine Found in natural sources Coffee Tea Kola nuts Cocoa beans
Tea Caffeine 5% by weight Soluble in hot water Tannins High MW phenolic compounds Soluble in water Cellulose Insoluble in water Other substances Chlorophyll, etc…
Tea LeavesTeaCaffeine in CH2Cl2CaffeineTannin Salts in WaterInsoluble Cellular Material Isolation Procedure Hot water CH 2 Cl 2 Na 2 CO 3 Heat
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 Na 2 CO 3 Heat ( gentle boil ) for 20 min Cover with watch glass and hold down, if necessary, with glass rod. DO NOT BREAK THE BAG!!
Isolation Procedure Decant the hot liquid into a 50mL beaker (not erlenmeyer flask) Wash with 10 mL hot water (instructor has hot water) Add wash water to extract Cool to room temperature!! Discard tea bags in waste container
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 lab!
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 accumulation 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 DCM. then … Combine the separated bottom layer with the DCM layer obtained previously
Isolation Procedure Add 0.5 g anhydrous Na 2 SO 4 to remove excess water 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 containers 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 Caution!
Inhalation: irritant, allergen, coughing, drowsiness, damage to the lungs, shortness of breath, labored breathing, loss of appetite and delayed lung edema 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 Potential Health Concerns
This was the last lab! Next week - Be prepared for the cumulative written final! Goggles Lab coat Pencil Calculator Eat before class! Wear yellow! Finally …