Practice Quiz 3_A

Practice Quiz 3_A - N N N O N O CH 3 H 3 C CH 3 Quiz 3 Chem...

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Unformatted text preview: N N N O N O CH 3 H 3 C CH 3 Quiz 3 Chem 143A, sect. A__ Name____________#____ Score_____ A student carried out the extraction of caffeine from tea leaves as follows: Four tea bags were boiled in 100 mL of distilled water with sodium carbonate for 10 minutes. Impurities known as tannins precipitated out in the form of sodium salts. After removing the tea bags and filtering out the precipitate, the aqueous solution was cooled to room temperature with an ice bath. An extraction was then performed in a separatory funnel with three washings of dichloromethane (CH2Cl2), each of 20 mL. The CH2Cl2 extractions were washed with NaOH, a procedure that helps to remove more tannins. The solvent was then evaporated off on a hot plate. The light green residue left behind had a melting point of 198201C, compared to the literature value of 238C for the melting point of caffeine. This residue was then sublimated under vacuum to yield a white crystalline substance corresponding to the pure product. The structure of caffeine is shown below in Figure 1.a white crystalline substance corresponding to the pure product....
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This note was uploaded on 02/27/2011 for the course CHEM 143A taught by Professor Whitesell during the Spring '08 term at UCSD.

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