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Lecture 3 PowerPoint Presentation

Lecture 3

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Lecture 3

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  1. Lecture 3 Chapter 5: Extraction Lecture Problem 1 Due Thursday This week in lab: Ch 4: Recrystallization & Melting Point Procedures 1 & 2 Ch 4 PreLab Due Quiz 1 Next week in lab: • Ch 4: Procedures 3 & 5 • Ch 5: Extraction, Procedure 1 • Ch 5 PreLab Due & Quiz 2

  2. Chapter 5: Extraction Extraction • “Pulling out” a component from a mixture • Used to isolated specific compounds • Used to purify a compound • Types: Liquid/liquid extraction, solid/liquid extraction Two day lab: Procedure 1: Separation of an unknown three-component mixture Procedure 2: Extraction of caffeine from tea or coffee

  3. Chapter 5: Procedure 1 Possible Unknowns: Separation of an unknown three-component mixture: • Acidic component (CO2H) • Basic component (NH2) • Neutral component Acids: Separate by acid/base chemistry Bases: Once separated and dry, take a m.p. of each to determine the identity. Take melting points the following week. Neutrals:

  4. Chapter 5: Procedure 1 Example: Separate these three components 1. Use a flow chart to visualize how the separation will work. 2. See photos/video.

  5. Chapter 5: Procedure 1 Once the separation is complete: • Dry each, weigh and calculate % recoveries (assume you started with equal amounts of each) • Take a m.p. of each to determine identities • Either take an IR of the acidic component OR an NMR of the neutral component

  6. Chapter 5: Procedure 2 Extraction of caffeine: 1. Use tea bags (odd # desks) or coffee bags (even # desks) 2. Steep tea or coffee bags in hot water 3. Extract aqueous solution with dichloromethane (CH2Cl2) to isolate caffeine • Purify caffeine by sublimation • Weigh caffeine. • Compare caffeine content in tea and coffee with hoodmate’s data; reference data. caffeine

  7. Chapter 5: Procedure 2 Extraction of caffeine: For extraction, use a separatory funnel; Get a demo from your TA. *A few, smaller extractions are better than one big extraction.* Vent funnel while shaking. Aqueous layer: tea/coffee solution Organic layer: dichloromethane/caffeine Separatory funnel

  8. Chapter 5: Procedure 2 Extraction of caffeine: Vent funnel while shaking. Point away from face, towards back of hood.

  9. Chapter 5: Procedure 2 Once caffeine has been isolated, purify via sublimation (heat solid  gas  pure solid). Weigh the isolated caffeine and calculate the amount of caffeine per gram of tea or coffee. Compare data with hoodmate; reference the data.