Purification and Identification of An Unknown Mixture
To separate a mixture of a neutral (ester, alcohol, ketone, aldehyde or ether) and an acidic compound (phenol or carboxylic acid) or a neutral and a basic compound (amine), and to identify the unknown mixture by physical (M.P. or B.P.) and spectroscopic methods (NMR, IR and MS).
The mixture (sample number: 27) was dissolved in 200 mL of CH2Cl2 and then extracted with 10% NaOH. The acid was removed by adding 3 x 50 mL of 10% NaOH. The neutral component in CH2Cl2 solution was set aside. The NaOH extracts were combined and then washed with 15 mL of CH2Cl2. The aqueous solution was acidified with 10% HCl. The solid yield (neutral component) was collected by vacuum filtration whereas the liquid yield (acidic component) was extracted into CH2Cl2 (3x25 mL). The acidic compound was then washed with 100 mL of water, dried over MgSO4, filtered. The solvent CH2Cl2 then was removed by evaporating it.
Purification of The Unknowns
The liquid yield (acidic component) was purified by fractional distillation. The boiling point of the compound was determined afterwards.
The solid yield (neutral component) was purified by recrystallization by using ethanol as the solvent. ~20 mL of ethanol was added to the solid. Water was then added to this solution drop wise until the solution turned cloudy. After that, ethanol was added drop wise again until the solution appeared clear again. To faster the recrystallization, the solution was put in an ice bath. The yield was then collected by suction filtration. The weight and the melting point were then recorded afterwards.
The mixture was not easily separated when extracted in CH2Cl2. An experimental error occurred when HCl was added to CH2Cl2 layer and cloudy solution, and not to the aqueous layer.
Component| Physical state| Colour| Soluble in| Weight(g)| B.P. (˚C)| M.P(˚C)| | | |...