Flashcards in Organic Chemistry- Separations and Purifications Deck (110)
What is one of the simplistways to separate out a desired product?
What is extraction?
The transfer of a dissolved compound (the desired product) from a starting solvent into a solvent in which the product is more soluable.
What is extraction based on?
The fundamental concept that like dissolves like. This principle tells us that a polar substance will disolve best in polar solvents, and a nonpolar substance will dissolve best in nonpolar solvents.
When performing extractions, it is important to make sure the two solvents are what?
What is immiscible?
They form two layers that do not mix, like water and oil
How do extractions work?
The two layers are temporarily mixed by shaking so that solute can pass from one solvent to the other.
What is the water layer called?
Aqueous phase (layer)
What is the nonpolar ether layer called?
Organic phase (layer)
How do you isolate the two phases once they have separated?
Use an equipment called a separatory funnel
Gravitational forces cause the denser layer to sink to the bottom of the funnel where it can then be removed by turning the top cock at the bottom.
What layer is most common to be on top?
Organic layer although the opposite can occur
The position of the layers is determined by what?
Their relative densities
Why are extractions done multiple times?
This is done in order to extract as much of the isobutyric acid from the ether layer as possible because it does not completely transfer with the first extraction . Multiple extraction with fresh water are more effective for obtaining the most product, rather than a single extraction with a larger volume of water.
Once the desired product has been isolated in the solvant, what is done?
We can obtain the product alone by evaporating the solvent, usually by using a rotary evaporator (rotovap)
What is a wash?
Perform the reverse of the extraction in order to removed unwanted impuries. A small amount of solute is used to extract and remove impurities rather than the compound of interest.
What does filtration isolate?
A solid from a liquid
How is filtration performed?
One pours a liquid-solid mixture onto a paper filter that allows only the solvent to pass through.
What is the result of filtration?
Left with the residue and filtrate
What is the residue?
What is the filtrate?
The flask full of liquid that passed through the filter
What is gravity filtration?
The solvent's own weight pulls it through the filter
When is gravity filtration used?
When the product of interest is in the filtrate
When is hot solvent generally used in filtration?
To keep the product dissolved in liquid
What is vaccum filtration?
The solvent is forced through the filter by a vaccum connected to the flask
When is vaccum filtration used?
When the solid is the desired product
Recrystallization is a method for what?
Further purifying crystals in solution
How is recrystallization performed?
we dissolve our product in a minimum amount of hot solvent and let it recrystallize as it cools.
How do you choose the solvent for recrystallization?
It should one in which the product is soluble only at high temperatures
Why is the solvent important in recrystalization?
When the solvent cools, only the desired product will recrystallize out of solution, excluding the impurities
When does distillation come in handy?
When the product itself is a liquid that is soluble in the solvent