Lecture 3
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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.

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Lecture 3

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Lecture 3

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

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

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 11

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 12

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

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 21

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 22

Chapter 5: Procedure 2

Extraction of caffeine:

Vent funnel while shaking.

Point away from face,

towards back of hood.


Chapter 5 procedure 23

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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