Caffeine Extraction

Edit Experiment

VIDEO LINKS:

Lab Experiments (Write protocols and perform experiments based on these):

  1. Extraction of Caffeine
  2. Thin Layer Chromatography of Caffeine Extract
  3. Solvent Removal by Distillation

Experimental Protocol

(Analysis) Watch the experiment videos.  Take notes on the protocol.  Stop the video and re-watch as necessary to acquire the details of the procedure.  Write out the protocol for each part of the experiment.  (It can be written in sequential steps.  Complete sentences are not necessary.)  This is the protocol you will follow, so be detailed.

Chemical Table

(Representation) Prepare your chemical table including the materials you will use in the experiment.  Here is a general template that you may use.  
Chemical Name Chemical Formula Structural Formula Molar Mass (g/mol) Hazards Reference Precautionary Statements
Acetone C3H6O 58.08 Flammable liquid, eye damage, target organ toxicity (central nervous system, kidney, liver, spleen, blood) fishersci Use in fume hood; Keep away form heat/sparks/open flames.
           
           
           

Equipment Table

(Analysis) Identify the equipment (type AND size) needed for the experiment and include the name and an image of each.  Be sure to describe the equipment, how to use it, and why it is suitable for this use.
Equipment Name Equipment Picture or Description Intended Purpose

Data Collection

  1. (Acquiring competencies) Following your detailed protocol based on the Extraction of Caffeine video, record your observations for the extraction. Note the pH of the drink before and after adding the sodium carbonate solution.
  2. (Acquiring competencies) Following your detailed protocol based on the Thin Layer Chromatography of Caffeine Extract video, record your observations for the TLC. Include an image of your TLC plate with baseline, solvent front line, and spot(s) indicated.
  3. (Acquiring competencies) Following your detailed protocol based on the Removal of Solvent video, record your observations for the solvent removal. Note the mass of the collecting flask before and after solvent removal.

Data Processing

  1. (Representation) Draw the structure of caffeine at low pH (~3) and at higher pH (~8).
  2. (Analysis) State which of the two structures is less water soluble.
  3. (Manipulation) Use your TLC plate to calculate the retention factor (Rf) values of each spot.
  4. (Interpretation) Describe your TLC plate and evaluate the purity of your caffeine extract based on your observation.
  5. (Assumptions) Find the amount of caffeine in your 5-hour energy drink on the label. Perform calculations, if needed based on serving size.
  6. (Manipulation) Calculate your percent recovery using the assumed value calculated above.
  7. (Existing knowledge, research, and views) Find the solubility of caffeine in water and in ethyl acetate. (include references)
  8. (Manipulation) Calculate the partition coefficient.
  9. (Manipulation) Based on the partition coefficient and the procedure you followed, calculate the maximum percent recovery that could have been obtained.
  10. (Assumptions)
Assumptions made Testing the assumption If assumptions are wrong ...
The samples were pure Recrystallize Melting point will change after recrystallization

Discussion

Write a minimum one-page (12 font, single spaced) discussion on the experiment conducted this week. Address at least one question in each category as fully as possible integrating the collected data, providing explanations for the observed trends, and evaluating whether your original assumptions about the experiment were validated by the results. The assignment will be graded on completeness, clarity of the explanations and the meaningful integration of the collected and calculated data. Correct grammar and appropriate format for the chemical formulae and chemical reactions is expected. You may use the outline included at the end of this document on how to build your essay to address each category.
  1. (Existing knowledge, research, and views) In addition to the caffeine and artificial flavor, the energy drink is also reported to contain many other ingredients. Look up the chemical structure of each ingredient and give a supported argument as to why none were extracted into the organic layer.
  2. (Analysis) Define partition coefficient. Provide at least one argument for having a large vs a small partition coefficient in an extraction.
  3. (Analysis) Provide at least two arguments for desired properties in a good extraction solvent.
  4. (Analysis) An organic compound with a pKa of 11 is only very slightly soluble in water. Predict the type of change in its solubility if water is replaced by a sodium bicarbonate solution (pH ~ 8-9) or a dilute acid solution (pH ~4-5). Justify your prediction.
  5. (Analysis) An organic compound with a pKa of 5.5 is only very slightly soluble in water. Predict the type of change in its solubility if water is replaced by a sodium bicarbonate solution (pH ~ 8-9) or a dilute acid solution (pH ~4-5). Justify your prediction.
  6. (Existing knowledge, research, and views) Identify at least one industrial method used to extract caffeine from coffee beans. Contrast your method vs. the industrial method and provide at least supported arguments for the advantages and disadvantages of each method.
  7. (Acquiring competencies) Propose at least one more method by which you could test the purity of the extracted caffeine. Provide a brief description of what the expected result of the method should be.
  8. (Analysis) Comment on the effectiveness of your caffeine extraction method and provide at least 2 reasons why your obtained amount of caffeine is different from the amount you expected based on the label on the container.
  9. (Experiment Design) Describe how a mixture of benzoic acid (pKa17), 2-naphthol (pKa 9.5), and naphthalene (neutral) could be separated using a combination of extraction and pH adjustments.
  10. (Analysis) Provide a supported argument for using a drying agent in the extraction. Predict what would happen without a drying agent.