Question

Benzaldehyde is used often as a fragrance in food. After opening, it rapidly becomes contaminated with benzoic acid, a normal product of autoxidation of the aldehyde. Outline a procedure that would allow you to separate the benzoic acid from an old, opened bottle of benzaldehyde. Specifiy reagents, but not quanitites or concentrations. Identify each technique to be used.

Answer 1

seperation of benzaldehyde from benzoic acid

Liquid–liquid extraction also known as solvent extraction and partitioning, is a method to separate compounds based on their relative solubilities in two different immiscible liquids, usually water and an organic solvent. It is an extraction of a substance from one liquid into another liquid phase.

mixture is treated with NaOH or NaHCO3

benzoic acid turns into sodium benzoate soluble in water benzaldehyde soluble in DCM

water layer with sodium benzoate is treated with acid to recover benzoic acid

DCM with benzaldehyde is evaporated

2. Column chromatography

3. simple distillation