Question

1.What hazard is created when an acid is reacted with sodium bicarbonate? Describe the procedure that you will use to minimize the hazard posed by the extraction of a carboxylic acid with dilute aqueous sodium bicarbonate?

2.What does the term, “like dissolves like” mean in the context of the extraction lab?

3.What type of solution would you use to extract an amine from an organic phase (e.g. methyl t-butyl ether)?

Answer 1

1. If you treat carboxylic acid with sodium bicarbonate you will get sodium salt of carboxylic acid and carbonic acid (H2CO3), they are not really hazard. Usually, to remove impurities we will make sodium salt of the carboxylic acid with sodium bicarbonate, then wash with ethers, So all organic impurities will go into ethers, then the aqueous layer of the sodium salt of carboxylic acid is neutralized with dilute Acid then extract into organic solvent such as ethyl acetate, Dichloromethane.

2. Like dissolves like means, organic compounds are dissolved in organic solvents such as ethyl acetate, chlorinated solvents, acetonitrile, ether, hexanes etc. inorganic compound are dissolved in water. In the case of extractions, non-polar compounds will extract in non-polar solvents like hexanes and ethers, polar compounds are extracted in polar solvents like ethyl acetate, DCM, chloroform, etc.

3. try making the aqueous layer basic (pH 10) and extracting it. This makes the compound the free base and more soluble in organic solvents. you can use ethyl acetate, little more polar solvents like DCM and Chloroform, even if it is not coming you can use a mixture of Methanol in DCM(dichloromethane)/Chloroform.