Question

1. (3) Acetone is a more polar solvent than diethyl ether. With reference to the structures and specific functional group(s) of each molecule, why is cholesterol more soluble in acetone than lecithin is?

2. (2) In step 3 of the “Extraction and purification of Cholesterol,” the egg yolk is mashed with a spatula. What is the purpose of this step? ( consider how it helps with the following step(s) )

3. (2) In step 7 under “Extraction and purification of Lecithin,” acetone is added to the ether solution. Briefly describe the purpose of this step and how it helps isolate pure lecithin.

4. (3) At the end of the reaction, you may have excess materials. Where should you dispose of each substance below?

Acetone:

Cholesterol:

Diethyl ether:

Egg yolk:

Lecithin:

Answer 1

1. (3) Acetone is a more polar solvent than diethyl ether. With reference to the structures and specific functional group(s) of each molecule, why is cholesterol more soluble in acetone than lecithin is?

Cholestrol has a polar hydroxyl group which can have H-bonding interaction with carbonyl oxygen and thus gets solublize in acetone whereas as lecithin is a mixture of glycerophospholipids having long hydrophobic chain of hydrocarbons and a polar head group. Therefore, show emulsification and lubricating property similar to soap and thus have lower solubility in polar solvents like acetone.

2. (2) In step 3 of the “Extraction and purification of Cholesterol,” the egg yolk is mashed with a spatula. What is the purpose of this step? ( consider how it helps with the following step(s) )

Meshing of egg yolk ensures the interaction of addded solvents with total lipids present in the yolk for extraction purpose. This separates solid in soluble residue from total lipids including cholestrol, fatty acids etc.

3. (2) In step 7 under “Extraction and purification of Lecithin,” acetone is added to the ether solution. Briefly describe the purpose of this step and how it helps isolate pure lecithin.

Lecithin are insoluble in acetone and gets solublize in ethers. Therefore can be filtered out from rest of the soluble components.

4. (3) At the end of the reaction, you may have excess materials. Where should you dispose of each substance below?

Acetone: It is highly flammable compound, thus should be labelled as hazardous waste and kept in closed containers

Cholesterol: In biohazard waste container

Diethyl ether: It is highly flammable compound, thus should be labelled as hazardous waste and kept in closed containers

Egg yolk: In biohazard waste container

Lecithin: In biohazard waste container