Quiz #4

Question 1

What is extraction?

Answer 1

A purification/separation technique that can be used to separate compounds based on their partitions between two media (one compound has more affinity toward one media than the other).

Question 2

What are the uses of extraction?

Answer 2

1. to extract a compound from a solid (ex. extraction of natural products)
2. to separate two compounds
3. to purify products after reactions (work up)

Question 3

What are the principles underlying extraction?

Answer 3

compounds have different solubilities in different solvents

Question 4

What are the types of extraction?

Answer 4

1. solid-liquid extraction
2. liquid-liquid extraction

Question 5

Describe solid-liquid extraction

Answer 5

• extract compounds from solid to liquid
• compound has higher affinity to be in the liquid phase

Question 6

Describe liquid-liquid extraction.

Answer 6

-two immiscible solvents
- solutes have different solubilities in different solvents
- dissolved compound will be partitioned between the two solvents
- mainly move toward the preferred solvent

Question 7

How is liquid-liquid extraction done in lab?

Answer 7

• extraction is done using a separatory funnel
• organic solvents and water (aqueous)
• polar compounds —> aqueous layer
• non-polar compounds —> organic layer
• usually aqueous layer is on the bottom except for halogenated organic solvents like DCM.

Question 8

Describe how Acetaminophen “Tylenol” and Sodium Chloride (NaCl) Mixture may be separated

Answer 8

• Acetaminophen “organic” is soluble in ethyl acetate (organic solvent) and insoluble in water
• NaCl is soluble in water but not in ethyl acetate
• upon extraction, each compound will move to the preferred layer

Question 9

What does the partitioning degree depend on?

Answer 9

the relative solubility of the compound in both layers

Question 10

What is the partition coefficient (K) an indication of?

Answer 10

the distribution of a compound in both layers

Question 11

What is the partition coefficient (K) equation?

Answer 11

K = C(organic) / C(aqueous)

K = (m0/V0) / (ma/Va)

m0 = mi - ma

Question 12

How does efficiency change with K?

Answer 12

As K increases, there are more efficient extractions

Question 13

Compare efficiency of multiple small extractions vs single large extractions

Answer 13

Multiple extractions with smaller volumes are more efficient

Ex. 3 extractions with 20mL is better than 1 extraction with 60mL

Question 14

Describe acid-base extraction.

Answer 14

• organic acids and bases “amines” are soluble in the organic solvent
• addition of bases converts acids into salts (carboxylates) —–> polar and moves them to the aqueous layer
• addition of acids converts bases into salts (protonated) —-> polar and moves them to the aqueous layer