Question

Okay, so we had solid benzoic acid, ethyl 4- aminobenzoate, and 9-fluorenone all dissolved in diethyl ether (4ml). We separated the basic component by adding 3M HCl, we separated the acidic component by adding 3M NaOH. I don't understand what happens here. To isolate the acidic solution, we added 6 M NaOH and used the vacuum to recover the solid. To isolate the basic solution we added 6M HCl. Here are the questions I am having trouble with...

• Why are each of the three solids (the carboxylic acid, the amine and the ketone) soluble in diethyl ether? Examine the structures of each solute and explain what factors increase solubility in water versus the organic solvent used. Identify the significant INTERMOLECULAR FORCES affecting solubility
• Explain why two layers formed when 3M HCl was added to the ether solution of the ketone, acid and base. What solvents do the two layers represent? Which solvent forms the upper layer? Why?
• Draw an equation to illustrate the chemical reaction that occurs when HCl was added to the ether solution.
• What chemical(s) dissolved in to the upper layer? What chemical(s) went in to the lower layer? Why?

Thank you so much!

Answer 1

Solubility of substance is based on the principle "Like to Like". This means polar solutes dissolve in polar solvents and non-polar solutes dissolve in non-polar solvents.

1. The structures of the given three compounds:

  

Since diethyl ether is a non-polar solvent so that fluorenone is non-polar solute is soluble.

Benzoic acid havind both polar and non-polar parts, the non-polar part dominate the polar part, sothat this is also soluble in ether.

Ethyle-4-aminobenzoate is the same case as benzoic acid.

In this case, there is a non-polar non-polar attraction

Among these three compounds, only benzoic acid is soluble in water. Because it has polar part also and hydrogen bonding is the responsible for solubility.

2. When HCl is added to the ether solution, two layers are formed because HCl is a polar solvent does not miscible with non-polar ether solvent.

One of the layer is non-polar organic ether layer and second one is polar aqueous HCl layer.

Those solvent having high density will be the lower layer and those having low density in the upper layer.

3. When HCl is added to the ether layer, it will react with Ethyle-4-aminobenzoate to make this more polar so that this is goes to aqueous HCl layer.

4. Since HCl has high density it will remain in lower layer so, ethyl-4-aminobenzoate present in this lower layer, and ether has low density it will on upper and fluorenone, benzoic acid present in this upper layer.