Chem

Experiment 1: Acid Base Extraction

Objective:

To learn the proper techniques of acid base extraction. Besides that is to identify the unknown compound and the melting points of the unknown sample and benzoic acid.

Introduction

Acid base extraction is a procedure using sequential liquid-liquid extractions to purify acids and bases from mixtures based on their chemical properties. In this experiment, the solution is altering the solutes to accommodate the solvents and the separation efficiency becomes almost quantitative.

Organic compound that have more than five carbons tend to be ether soluble and water insoluble. Salts and other molecules with more than one functional group have the reverse solubility characteristic. They tend to be ether insoluble and water soluble. This extraction technique is used to separate the mixtures. The mixture is dissolved in ether. The amines are converted to water soluble salts with hydrochloric acid and are extracted in the water layer. Then the organic acids are neutralized to water soluble salts with sodium hydroxide and extracted in the water layer. Finally, only the neutral compounds remain in the ether and are recovered by distilling off the ether.

The basic aqueous solution is added with concentrated hydrochloric acid to yield carboxylic acid which because of its water insolubility precipitates out. It can then be collected, recrystallized and then allowed to dry to yield the pure carboxylic acid.

Procedure:

First extraction

1. 0.24 g of unknown sample and 0.12 g of benzoic acid was weigh and placed in a test tube.

2. 10 ml of ether was added to the mixture and it was shaken to dissolve the mixture. The solution then was transferred to the separatory funnel and 5 ml of 1M NaOH was added.

3. It was capped tightly and the layer was mix by swirling and shaking it gently for 30 second. The pressure inside the separatory funnel was vent out by tilting the funnel and the stop cork was open.

4. The process...