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Purification Techniques CHEM 241-08B, (Video: https://www.youtube…
Purification Techniques CHEM 241-08B
DISTILLATION
Technique
Overview:
Distillation is used almost ubiquitously among lab spaces to separate mixtures. It is important because it is used for purifying and for identifying certain organic compounds.
How it's done:
It is a fairly straightforward procedure. Liquid compounds are heated, producing vapors. These are cooled in a condenser. Thus, the desired compounds are separated and identified.
Pros and Cons
Pros:
(1) Is a cheap process; (2) Can be reused.
Cons:
(1) Requires a lot of energy for large samples; (2) sometimes 100% separation is not attained
When to use this technique:
(2)
If you want to remove a volatile compound(s) from nonvolatile compound(s) distillation is the most simple method for this goal.
(3)
You want to separate volatile product from nonvolatile impurities
(1)
Separate 2+ volatile compounds have distinct boiling points.
TECHNIQUE VIDEO
COLUMN CHROMATOGRAPHY
TECHNIQUE
OVERVIEW: Column Chromatography is a technique used to separate mixtures of compounds based on the differences in their polarities and their affinities (Affinity is the tendency of a chemical species such as an atom or molecule to react with another to form a chemical compound) for a stationary phase and a mobil phase. This process is important because we are able to purify liquids.
PROS/CONS OF USING: Pros: The items in the experiment are easily disposable, and the price range for everything in the experiment is relatively low cost Cons: It is a relatively time consuming process, it can get expensive depending on how far you wish to take the experiment it also has a low separation outcome.
WHEN TO USE THE TECHNIQUE: This technique can best be used for separating colored substances, solid or liquid. With the stationary phase, Alumina can be used as a solvent. Likewise, in the mobile phase, hexane can be used as an organic solvent.
HOW IT'S DONE: Column Chromatography is a fairly simple procedure. Essentially you will first prepare the sample you wish to use in the experiment by weighing each of the mixtures and then placing them into a sample vial. While adding 3-5 drops of Dichloromethane and mix to make a slurry. To get the Dichloromethane to evaporate you can add alumina to the mixture. After the sample is prepared, you can then place it into the funnel for the column chromatography, and let the sample flow through. After all of the product has been collected you will place it in a hot water bath to allow solvent to evaporate. After cooling it is time to weigh the crystals that have formed throughout the experiment.
VIDEO: (
https://www.youtube.com/watch?v=1Nbhnt9llGQ
)
Technique
Overview:
1) Choose a suitable solvent/ solvent pair; 2) Dissolve the solute by heating; 3) Decolorize with activated charcoal; 4) Rapid/ hot filtration; 5) Crystallize the hot saturated solution; 6) Filter crystal & air dry; 7) weight crystals, calculate % yield, obtain mp
Pros and Cons:
Pros: powerful purification technique, multiple types of this method, Cons: purifies one component, yield is limited by phase equilibria
When To Use:
Crystallization is used as a purification technique for solids
Technique
Overview
: Extraction is often used as one of the steps in isolating a product of an organic reaction. Essentially, it is when a substance is "pulled out" from one liquid by another liquid. It is also required that both of the liquids are insoluble in each other. There are two types of extractions that we studied in lab: Macroscale and Microscale extraction.
How a Macroscale Extraction is done
: A separatory funnel is used to hold an ether solution. An organic layer and aqueous layer are formed. The extraction is performed when the separatory funnel is stoppered and gently turned upside down in order to mix the contents. From here on, the desired layer can be extracted from the mixture and a product can be isolated.
How a Microscale Extraction is Done
: A similar process as the macroscale extraction except a centrifuge tube is used and the bottom layer is extracted using a centrifuge tube.
Pros/Cons
: The pros include that it is a cheap and quick method. It is also fairly simple to perform. The cons are that it is easy to mistakenly collect impurities with your extract. This would lead to analytical complications.
When to use this technique
: This technique can be used to identify an unknown compound. It can also be used to easily recover a valuable substance from its original solution.
VIDEO
:
https://www.youtube.com/watch?v=E33gCnnsOmM
Video:
https://www.youtube.com/watch?v=AY38ih4tR1k
CRYSTALLIZATION
Extraction