Steam bath step 13 the liquid bubbled then evaporated

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Steam bath (step 13) - The liquid bubbled, then evaporated until only white flakes remained on the beaker - Mass of powder: 3.54 g Part B Sublimation (Step 18) - Dry ice: crumbly, white solid - The sublimation took a few minutes but eventually the white flake disappeared off the bottom of the beaker and a white solid appeared to be forming on the bottom of the cold finger - When scraped off the cold finger, caffeine crystals were fine, white crystals - Mass: 0.005 g Part C TLC (step 26) - 99:1 acetone: acetic acid; a clear, colorless solution - 80:20 acetone: acetic acid; a clear, colorless solution - TLC points were very unclear* - Melting point: 238-244ºC TLC results were taken from an adjacent group.
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Tables of Results: Caffeine extraction results Compound Molar mass (g/mol) Quantity (g) Mmol Yield (%) Melting Point (ºC) Caffeine (purified) 194.19 0.005 1.023 2.08% 238-244 * Please note that all TLC results and diagrams presented in this report come from borrowed data provided by Kitty Chan (300018510) and Andrew Hanna (300005439) Caffeine extraction TLC results (99:1 acetone: acetic acid) Sample Observed Rf Value (cm) Crude Caffeine (CC) 1.0 Sublimed Caffeine (SC) 0.74 Reference Caffeine (RC) 0.68 Caffeine extraction TLC results (80:20 acetone: acetic acid) Sample Observed Rf Value (cm) Crude Caffeine (CC) 1.0 Sublimed Caffeine (SC) 0.67 Reference Caffeine (RC) 0.65 TLC Plates:
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Sample Calculations Mass of Tea leaves: Mass of tea = Mass of tea and bags – (mass of tea bags x 2) Mass of tea = 6.23 g – (0.120 g x 2) Mass of tea = 5.99 g Mass of purified Caffeine Mass of purified caffeine = mass of watch glass and caffeine – mass of watch glass Mass of purified caffeine = 37.895 – 37.890 g Mass of purified caffeine = 0.005 g Mmol Conversion Mmol conversion = (Quantity of Caffeine / Molar mass of Caffeine) x 1000 Mmol conversion = (0.005 g / 194.19 g/mol) x 1000 mmol Mmol conversion = 0.026 mmol Percent Yield of Caffeine a) Theoretical yield = Mass of tea x 0.04 Theoretical yield = 5.99 g x 0.04 Theoretical yield = 0.2396 g b) Percent yield = (Actual yield of caffeine / Theoretical yield of caffeine) x 100% Percent yield = (0.005 / 0.2396) x 100% Percent yield = 2.08% Rf values Rf RC (99:1 acetone: acetic acid) = d RC / d S Rf RC (99:1 acetone: acetic acid) = 3.2 cm / 4.7 cm Rf RC (99:1 acetone: acetic acid) = 0.68
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Flow Chart Discussion
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The goal of this experiment was to purify caffeine from tea leaves. As explained above, tea leaves are composed from a variety of compounds, each with differing chemical properties. This led us to begin this process by initially introducing the tea bags into a beaker of boiling water, which allowed for the separation of caffeine from the non-water soluble components such as chlorophylls and cellulose. Next, sodium carbonate was introduced into the steeped tea solution. This relatively strong base was effective in initiating an acid-base reaction with the slightly acidic catechins present in the solution. As these catechins were deprotonated, their ionic nature significantly increased and became exclusively miscible with water. This led to the natural separation of these compounds when dichloromethane, an organic solvent, was introduced into the funnel, commencing our liquid-liquid extraction. With the caffeine being in the organic
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