Lab 2: Extraction Flashcards
Liquid-liquid extraction is based on what?
Difference in solubility of the components in two immiscible solvents.
What characterstics must the two solvents possess?
1) The first solvent should completely dissolve both compounds in the mixture.
2) The second solvent must be immiscible with the first solvent AND dissolve only one component of the original mixture, and dissolve it better than the first solvent.
How do we ensure maximum separation of two compounds? What is partition coefficient of extraction
By making equal portions of the second solvent and doing successive extractions. Partition coefficient of extraction is the ability for the compound you want to extract in the second solvent to dissolve in the first, which leads to ineffective separation of compounds.
What does a two-phase system mean?
Usually consists of an aqueous phase and an immiscible organic phase, the compound being isolated being extracted into the organic phase.
What can an organic solvent be typically?
Diethyl ether, chloroform, petroleum ether etc.
How do we get rid of emulsion line? What is saturated NaCl?
1) Saturated NaCl will break up emulsion line because it is much less soluble in organic solvent than water and hence will pull the water out of the organic layer.
2) Wait 10-20min and swirl flask gently until emulsion line breaks up
After extraction, how do we dry the organic solvent?
Add a drying agent such as magnesium sulfate (stronger drying agent) or sodium sulfate. These inorganic salts form hydrates by absorbing the small amount of water in the organic solvent
What is the drying procedure? How can we tell if you added enough drying agent?
First, never exceed 1/10th of the liquid volume or else it might absorb your desired organic solvent. Add just enough agent to have some agent that moves freely as individual grains. Wait 5-10min and then filter off drying agent by gravity filtration.
What does aqueous HCl do to benzocaine? How is this base regenerated?
Aqueous HCl turns benzocaine into an ionic salt, which is more soluble in water than ether. After the”salt of base fraction” is neutralized by adding NaOH (now base fraction). This reaction generates a lot of heat. Cool before adding it to funnel. This can then be extracted by using diethly ether solvent with the top layer being the desired solvent.
