Your Morning Cup of Coffee! Solubility of Caffeine in Various Organic Solvents

Overview

Objectives/Goals The purpose of this experiment is to compare the solubility of caffeine in liquid CO2, 1,1Difluoroethane and Methyl Alcohol. I believe that methanol will be the best solvent and liquid CO2 will be the worst because caffeine is a polar molecule and methanol is a polar solvent. Methods/Materials I made packages of powdered caffeine tablets in coffee filters and soaked them in 5 milliliters of each solvent. My apparatus for liquid carbon dioxide is a thick plastic test tube screwed to a soda bottle cap with a brass needle sticking into it. The needle is attached to a 4-way brass pipe attached to a pressure gauge, a manual pressure release valve and an automatic pressure release valve good for up to 100 psi. Dry ice begins melting in the setup at approximately 60 psi. I weighed sample boats in a Mettler Balance, soaked the caffeine packets in the solvents, added the liquid to the sample boats, let it evaporate, and weighed the boats again. Then I recorded the difference. I tested the samples for fillers with sodium hydroxide and for caffeine with Dragendorff's Reagent. Results All the samples left a residue. The residue was caffeine with no fillers. I found that the longer I left the packets in, the bigger the sample was up to a certain point when the solvent became saturated. My hypothesis was correct and methanol was the best solvent. Liquid CO2 was the worst. By accident, I also discovered that some brands of tonic water do not contain quinine even though the labels say they do. Conclusions/Discussion Although CO2 is the worst solvent, it is very useful in factories because it can be kept under very high pressure (2000 psi) and heated to 100 degrees F and it will become supercritical, which makes it a better solvent. It is also completely non-toxic and is a gas at room temperature so cannot leave any bad tastes or residues. Difluoroethane is nasty because even though it is a gas at room temperature it is addictive and explosive. When it explodes it creates very toxic gases. Although methanol is a very good solvent for caffeine, it is flammable and must be evaporated or boiled off because it is a liquid at room temperature. Also, it is very toxic. I think that the best solvent for caffeine would be dimethyl ether because it does not form explosive peroxides and is very polar.

Awards (1)

• Third Place

Competition history

• CSEF 2011 Chemistry · Entry J0617

Resources

• CSEF project summary ↗

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