Question

1. Outline a separation scheme for isolating pure caffeine from tea. Use a flowchart that begins with the tea bag and ends with the pure caffeine. Explain what is being separated at each step throughout the procedure. 2. Why was the sodium carbonate added to the tea solution? 3. The crude caffeine isolated from tea often has a green tinge. Why? 4. What are some possible explanations for why the melting point of your isolated caffeine was lower than the literature value (236°C)?

Answer 1

solution Теа | - heat in boiling water (15 minutes) add methylene chloride (CH₂Cl2) so caffeine preferentially dissolve in CH₂ Cl₂ add Na, CO3 csodium carbonate) - so tannins which hydrolysed of form acid with water reacts with NaCO3 & form salt , soluble in aqueous solution two layeus will form, at bottom organic layer of methylene chlonde & caffeine f top one of aqueous solnt Tannens using pipet organic layer is separated add na sou which will dry the organic soln on heating low Melting point Chill, will vaporized at ~ 40°C imbuvel caffeine ! on sublimation pure caffeine