Question

1. After an extraction is completed and the two immiscible liquids are formed when placed on a ring stand, the ammonium salt product is in the acidic layer. What must be done with the organic layer upon separation?

2. Regarding the above TLC, would you expect the product to be more or less polar than starting material? In general, what has happened in this reaction?

3. An organic compound RCOOH functional group has a pK_a ̴ 5 was extracted with sodium bicarbonate, would the salt formed be in the aqueous or organic phase? What can be added to recover the RCOOH?

Answer 1

3)

Extraction is separation of organic mixtures. An organic compound RCOOH (carboxylic acid) with pKa about 5 is extracted with sodium bicarbonate, the salt (carboxylate ion) formed will be soluble in the aqueous phase. Because the ionic form is soluble in an aqueous phase and other non-ionic organic compounds in the mixture will remain dissolved in the organic phase.

If we want to recover RCOOH from the salt we have to add HCl to the aqueous phase. The carboxylate ion will be protonated by HCl and results in the formation of the original carboxylic acid (RCOOH).