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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

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

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:

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.

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

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

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

Chapter 5: Procedure 2

Extraction of caffeine:

Vent funnel while shaking.

Point away from face,

towards back of hood.

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.

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