Caffeine Isolation of a Natural Product

 

Caffeine Isolation of a Natural Product

Purpose

This lab aimed to become familiar with the isolation of natural products by the practice of science. By isolating the caffeine through a step-by-step process of salting, boiling, separating from an aqueous layer, distillation, and melting point checks, we were using almost every skill acquired since the beginning of the semester. If time were to permit, recrystallization would be done as well. This lab provided an in-depth understanding of how to separate an organic compound that is found naturally occurring with acidic features.

Chemicals and Equipment

  • Methylene chloride Na2CO3
  • Anh Na2SO4 Acetone
  • Hexanes
  • Tea bags (7) Beaker, 400 or 600 ml
  • Heat-resistant gloves Hot-plate
  • Tongs Stirring rod or spatula
  • Ring stand with ring Separatory funnel with stopper
  • Funnel with cotton plug Erlenmeyer flasks, 125 mL (2)
  • Hot water bath Simple distillation set up with 100 mL RB flask
  • Ice bath Buchner funnel
  • Filter paper Side arm filter flask

Standardization of Potassium per Magnate

Procedure

1) Immediately on arrival at the lab, 200 ml of water and 5 g of Na2CO3 were added to a 600 mL beaker flask. Put the flask on a hot plate set on high power and monitor it up to boiling. When the boiling began then turned down the power to medium

2) 7 tea bags were taken and then strung together with a single overhand knot, each bag had roughly 2.5 g of tea, of which about 3% was caffeine

3) Cluster of tea bags was put into the boiling water and allowed the water to boil for 15 minutes to make a very strong tea. Water lost by boiling was replaced with fresh water to keep the water level constant

4) The hot plate was turned off and, using the heat-resistant gloves, the beaker was taken off of the hot plate and put into an ice bath to cool down below the room temperature

5) When the tea bags were cooled enough to handle, we removed them from the tea and carefully squeezed as much liquid out of them as we could by using tongs without breaking any bag

6) Using a funnel, the chilled strong tea was transferred to a separatory funnel in its ring stand and added 20 ml, of Methylene chloride (CH2Cl2)

7) The Sep, funnel was stoppered, then it was taken out of the ring stand, turned completely upside down, and opened the stopcock to vent it

8) After closing the stopcock, swirled the sep, funnel carefully

9) Then the sep, the funnel was put back into the ring stand, removed the stopper, and allowed the phases to separate

10) The Methylene chloride was drained from the bottom of the sep. funnel into a 125 mL Erlenmeyer flask, for minimizing the amount of water in the Methylene chloride

11) The Methylene chloride extraction was repeated twice more with fresh 20 mL portions, combining all three extracts in the same Erlenmeyer flask

12) 5 g of anhydrous Na2SO4 was added to the Erlenmeyer flask and swirled to dry the extract of traces of water. When all of the Na2SO4 made clumps, added another 5 g of Anh. Na2SO4 and swirling were continued

13) then poured the dried Methylene dichloride solution through a funnel with a small plug of cotton into a pre-weighed 100 mL round-bottomed flask. The Erlenmeyer flask was tapped with a spatula to help disturb the drying agent and transferred as much solution as possible

14) An additional 5 ml of fresh Methylene chloride was used to rinse the Erlenmeyer flask and poured this rinse through the funnel as well

15) A simple distillation apparatus was set up learned previously. The weight of the distillation flask was understood

16) The Methylene chloride was distilled quickly, being careful to remove all the Methylene chloride

17) The heating Mantle was removed and allowed the flask containing the crude caffeine to cool down and then disassembled the distillation flask

18) After it was cooled down, the distillation flask was weighed and calculated the yield of crude caffeine

19) Then 5 ml of acetone were added to the flask with the crude caffeine and heated in a hot water bath to dissolve the caffeine

20) Solution was filtered as there was a small amount of solid that looked different from the bulk of the crude caffeine, into a small Erlenmeyer flask through a warm funnel with a small, loosed plug of cotton in the stem, by using another mL of hot acetone to rinse the flask and filter

21) Keeping the acetone solution hot in the hot water bath, added hexane drop-wise to the “cloud point”, until the solution stayed distinctly cloudy when well mixed and still hot

22) The flask was cooled in an ice bath and allowed crystals to form

23) The caffeine crystals were filtered through a piece of filter paper in a Buchner funnel, using hexane to transfer more material from the flask and rinsed the product

24) The caffeine was transferred from the filter paper to pre-weighed watch glass and dried in the oven to constant weight

25) The weight and MP of the final product were determined

Results

Weight of round bottom flask = 54.20 g

Weight of flask + crystals = 54.46 g

Weight of crystals = 54.46 – 54.20 = 0.26g

Each bag of tea contains caffeine = 55 mg

Total caffeine in 7 bags = 385 mg = 0.385 g

Percentage recovery = x 100

= 0.26/0.385 x 100

= 67.5%

Experimental M.P of caffeine = 222 – 223 oC

M.P of pure Caffeine = 234- 236 oC

Discussion

From the experimental performance, the isolation of natural products was carried out by using the isolation procedure. The percentage recovery was 67.5%. The experimental caffeine calculated content was lower as a proportion of mass. This could be the result of some errors made during the experiment.

  • When the aqueous tea solution was moved from the flask to the separatory funnel, not all of the caffeine was transferred when it was rinsed with water, which could be a source of error
  • Another probable source of inaccuracy is that the separatory funnel was not swirled twice during the general extraction operation
  • . When adding dichloromethane to the solution, the separatory funnel was not spun at first, as instructed in the laboratory manual, but was instead inverted immediately. This could cause less caffeine to dissolve in the organic layer, resulting in a low mass percentage.
  • During the drying, some caffeine crystals might sublime due to overheating

In the end, the overall experiment was very interesting and informative as we were not familiar with the extraction process and the proceedings.

 

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