Answer to Question #254928 in Biochemistry for andy

Question

4. In organic chemistry and biochemistry labs, diethyl ether (CH₃CH₂OCH₂CH₃) and water (H₂O) are often used to do liquid/liquid extractions. These two liquids form two layers or are immiscible.  

(a) Why are they immiscible, i.e. why do they form two layers?

(b) You are extracting Vitamin Alpha and Vitamin Omega from a new microbe that has been discovered in an underwater steam vent and find that (i) Vitamin Alpha separates into the water fraction, what functional groups would you expect on it? Why? (ii) You find that Vitamin Omega separates into the diethyl ether fraction, what functional groups would you expect to find on it? Why?

Answer 1

4.a) Diethyl ether and water are not soluble with each other as both lack H-bonding. The presence of bulky ethyl group around O-atom in ether prohibits the formation of intermolecular hydrogen bonding between ether and water. As a result the form two separate layers upon mixing.

4.b.i) As vitamin alpha is soluble in water, it may contain highly polar functional group like hydroxyl group which can form H-bonding with water. Due to formation of intermolecular H-bonding, it remains in aqueous layer.

4.b.ii) As vitamin omega is present in diethyl ether, it may contain non-polar or less polar functional group like alkene. This vitamin has greater interaction with ether and it remains in organic layer.