Acid-Base Extraction

INTRODUCTION :

Extraction is a process of transferring a solute from one solvent to another or frequently used to separate one or more components from a mixture. Extraction is accomplished by shaking a solution in a separated funnel with a solvent that is immiscible with the one in which the desired substance is dissolved and in which the desired substance is more soluble. Two liquid layers are formed which can be separated from each other by draining the lower layer through the stopcock of the separated funnel.

In this experiment, we used the best for extracting organic solutes which is ether (diethyl ether) because it is chemically very stable, has a low boiling point and excellent solvent for most organic compound. Separating a mixture of an acid (benzoic acid) and a neutral compound (triphenylmethanol/1,2,4,5-tetrachlorobenzene/unknown sample) into its components by extraction. The mixture is dissolved in diethyl ether and both components are soluble in this solvent. Then a 1M NaOH solution is used to extract benzoic acid in the form of its water soluble salt, sodium benzoate, leaving the neutral compound in ether layer.

OBJECTIVES :

1. To determine the analysis of acid base extraction.

2. To separate a mixture of two organic compounds, purify them and then characterize them from their melting point.

PROCEDURE :

About 0.24 g of unknown sample and 0.12 g of benzoic acid are weighed and placed in a test tube. 10 ml ether was added to the mixture and the test tube was shaken to dissolve the mixture. Then the solution was transfer to the separatory funnel and 5 ml of 1M NaOH was added, tightly capped it, and the layers were mixed by swirling and shaking gently for 30 seconds. Any pressure was vented by tilting the funnel and opening the stop cork. The stop cork was closed, shaken and vented again. The mixture was stood to allow the layers to separate. The top layer was the ether layer and the bottom layer was the aqueous layer. The aqueous layer was drain...