Group mates: Date of Submission: November 28, 2012
Experiment No. 1
ISOLATION OF CAFFEINE FROM TEA
Caffeine is a very common substance and is found in coffee, tea, soft drinks, chocolate, and "stay-awake" pills such as Vivarin. It can be synthesized or isolated from natural sources. Caffeine constitutes approximately 4% of tea and coffee leaves, and is also found in cola nuts and cacao beans.
Caffeine is a member of the class of compounds organic chemists call alkaloids. Alkaloids are nitrogen containing basic compounds that are found in plants. They usually taste bitter and often are physiologically active in humans. Caffeine belongs to the family of heterocyclic compounds known as purines. It has the systematic name 3,7-dihydro-1,3,7-trimethyl-1H-purine-2,6-dione; it is also known as 1,3,7-trimethylxanthine, and 1,3,7-trimethyl-2,6-dioxopurine. Caffeine can be classified as an alkaloid , a term used for substances produced as end products of nitrogen metabolism in some plants. The chemical formula is C 8 H 10 N 4 O 2 . Caffeine has a molar mass of 194.19 grams (6.85 ounces). It is soluble in water and in many organic solvents, and it appears in pure form as white crystals. Caffeine can be prepared by extraction from natural sources or by synthesis from uric acid.
The objectives involved in this experiment is to gain experience in using extraction as a method of separation, to assemble and use a simple distillation setup in the separation volatile substances from non-volatile materials, to determine the boiling pint of a liquid sample and to isolate caffeine from tea and gain experience in chemical laboratory manipulation of plant materials. II Materials and Methods
The materials used in this experiment are the following:
* 10 pieces of tea bags(20 g)
* 175 distilled water
* 30 mL Chloroform (2 sets of 30 mL)
* 12.5g Sodium Carbonate
* Sodium Sulfate
* Separatory Funnel
* Distillation setup
* 250 mL Erlenmeyer Flasks
* 400 mL Beaker
* 25 mL Graduated Cylinder
* Evaporating Dish
* Watch Glass
* Boiling Chips
* Protective gears (lab gown, fume hood, goggles)
The methodology used in this experiment is only a simple extraction of caffeine which was started by preliminary extraction of 10 tea bags with 175 mL distilled water, heated until it boiled. It was followed by the liquid-liquid extraction using chloroform in a separatory funnel. It was done by carefully putting the aqueous extract in the separatory funnel and extracting it using 30 mL chloroform. It was repeated for the second time. The two resulting extract was combined and small amount of sodium sulphate was added for the final step before the distillation takes place. The last part was the distillation and the distillation set up was used to distil the chloroform. The extract was heated until it evaporated and until the greenish –white crystal appeared.
III Results and Discussions
Brand and weight| Lipton Tea , 20 g|
Flavor| Clear Green|
Pre-weighed evaporating dish| 39. 1680 g|
Weight of dish with the caffeine| 39.2236|
Caffeine (Actual Yield)| 0.0556 g |
Theoretical Yield| 0.7080 g of caffeine per tea bag|
Resulting boiling point of Chloroform | 58oC-60oC|
Percentage yield: 0.0556g caffeine0.7080g x 10 tea bags x 100% = 0.7853% or 0.79%
I.- Solid-Liquid Extraction
The 10 tea bags were prepared for boiling to get the extract. As the tea bags were dipped into the distilled water, the first physical change occurred and observed was the change in color of the water from clear to a dark brown. When it boiled, the boiling solution produced smell from the tea itself.
II and A - Liquid-Liquid Extraction and Distillation
This took place in a fume hood with a separatory funnel containing the combined...