Caffeine from tea

Compare the following excerpts that describe the process of recrystallization for product purihcation. The hrst excerpt is adapted from an undergraduate laboratory experiment involving the extraction of caffeine from tea leaves. The last two, written for expert audiences, are taken from articles in The Journal of Organic... 

Caffeine from tea, originally named theine, is isolated. 

The isolation of caffeine from tea leaves follows the scheme below ... 

Isolation of Caffeine from Tea Leaves Typical Procedure ... 

HPLC on an octadecyl column can be applied to the analysis of caffeine from tea or cola syrup (Chapter 8—use 20% methanol, 0.8% acetic acid, and 79.2% water as eluant), the acetylation of cholesterol (Chapter 10) pulegone and citronellal from citronellol (Chapter 25), cholesterol from gallstones (Chapter 22), the isolation of eugenol from cloves (Chapter 28— use 10% methanol, 5.4% acetic acid, and 84.6% water as eluant), isolation of lycopene and /3-carotene (Chapter 9), and the product obtained from enzymatic reduction of ethyl acetoacetate (Chapter 59). 

EXPERIMENT 13A Extraction of Caffeine from Tea with Methylene Chloride 103... 

In this experiment, caffeine is isolated from brewed tea or coffee using solid phase extraction (Technique 12, Section 12.14). It is offered as a Green Chemistry alternative to the procedure given in Experiment 13A in which methylene chloride is used for the extraction of caffeine from tea. 

Tea yields better-quality caffeine than that obtained from coffee. Caffeine from tea is relatively colorless, whereas the caffeine extracted from coffee is highly colored. About 25 mg of caffeine is isolated in either case. Sublimation removes much of the color from the tea and coffee samples. 

EXPERIMENT 13B (OPTIONAL) Ejctmction of Caffeine from Tea or Coffee Using Solid Phase Extraction (SPE) 107... 

Note to the instructor It is recommended that the C-18 silica in the SPE columns not be reused. See footnote 3 for information on the expected yield of caffeine from tea and coffee. 

Outline a separation scheme for isolating caffeine from tea. Use a flowchart similar in format to that shown in Technique 2, Section 2.2. 

Another green approach involving technology is the use of solid-phase extraction (SPE) columns (see Technique 12, Section 12.14). Using SPE columns, extractions such as removing caffeine from tea can be carried out more quickly and with less-toxic solvents. In other applications, SPE columns can be used to carry out the synthesis of organic compounds more efficiently with less use of toxic reagents. 

For experiments in which a compound is isolated from a particular source and is not prepared from other reagents, some information described in this section will not be applicable. Such experiments are called isolation experiments. A typical isolation experiment involves isolating a pure compound from a natural source. Examples include isolating caffeine from tea or isolating cinnamaldehyde from cinnamon. Although isolation experiments require somewhat different advance preparation, this advance study may include looking up physical constants for the compound isolated and outlining the isolation procedure. A detailed examination of the separation scheme is important here because it is the heart of such an experiment. 

The following steps are used with an SPE tube to remove caffeine from tea or coffee (see Figure 12.18) ... 

Some experiments, such as Experiment 13, are divided into two or more individual parts that are designated by the experiment number and the letters A, B, etc. In some experiments, like Experiment 13, each part is a separate but related experiment, and you will most likely perform only one part. In Experiment 13, you would do Experiment 13A (Isolation of Caffeine from Tea Leaves) or Experiment 13B (Isolation of Caffeine from a Tea Bag). In other experiments, for example Experiment 32, the various parts can be linked together to form a multistep synthesis. In a few experiments, such as Experiment 22, the last part describes how you should analyze your final product. 

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