Organic Chemistry: Lab Techniques, Separations and Spectroscopy Flashcards Preview

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Flashcards in Organic Chemistry: Lab Techniques, Separations and Spectroscopy Deck (34):

Describe Liquid Liquid Extraction:

When you use a particular compound's solubility as a means to separate it from other compound via using solvents which are both polar and non-polar.


What helps determine a compound's relative solubility in 2 different solvents?

Distribution Coefficient


What is a subset of liquid liquid extraction?

Using weak acid and weak base solutions


Describe how you would extract organic amines?

1) Use 10-15% HCl (strong acid diluted in H2O)
2) This reacts with amine to protonate it
3) Protonated amines can then be soluble in the aqueous solution and be extracted.


How do you extract carboxylic acids?

1) React with 5% NaHCO3
2) The carboxylic group will be deprotonated
3) Na+ will attach to the deprotonated Carbolylic acid and thereby will be soluble in the aqueous solution
4) H2O and CO2 are the byproducts
5) Extract


How do you extract phenols?

1) React with NaOH
2) Deprotanate phenol
3) Deprotonated phenol will then be soluble in the polar solution
4) Extract


What is a rule of thumb to remember when extracting phenols, carboxylic acids, and amines?

The weaker the acid or base you are trying to extract, the stronger the acid/base you need in order to extract said base. Inverse relationship.


What is a common solvent that these organic compounds are dissolved in?

Diethyl Ether


What concept does Thin layer chromatography use?

capillary action


Name the components in TLC, and the roles they play

1) Stationary phase (SiO2) functions as a stationary phase which helps to attract polar molecules
(polar itself)
2) Solvent which carries non-polar molecules


More polar compounds in TLC:
Less polar compounds in TLC travel :

slower, faster


What helps to calculate the relative polarity in TLC?

Rf=(distance that dot travels from the beginning point to it's max distance) over (how far solvent has traveled)


What do you use to separate larger bulk amounts of material in solutions?

Column Chromatography


Describe differences between column chromatography and TLC

1) Column filled with silica gel used (which is first submerged in organic solvent of choice with all the compounds you want to separate
2) Then you keep adding solutions one by one which increase in polarity until all your compounds have flown down.


In column chromatography, which compounds flow down the fastest?

The least polar


Describe Ion Exchange Chromatography's purpose

Ion Exchange Chromatography can be used to separate proteins.


What are the main components of Ion Exchange Chromatography

1) Polymeric Bead that is either positively charged or negatively charged
2) A solution of certain pH that contains chanrged (+ or -) and uncharged compounds that is flown through the polymeric beads
3) You can guess what happens next LOL


What are differences between HPLC and TLC?

1) HPLC uses pressure to make sure that the mobile phase moves faster across the stationary phase, so that in the end, you will get faster results
2) The mobile phase in this particular reaction is MORE polar than the stationary phase... which leads to....
3) More polar compounds reaching the "end" faster
4) You have a computer thing in the end that calculates which compound came out first. This is called Chromatogram


What are the actual physical components of a HPLC set up?

1) Pump (provides shit-tons of pressure to push mobile phase through)
2) Injector, in which you inject your mobile phase
3) HPLC column which contans stationary phase
2) Detector that comes after HPLC phase that connects to a computer
4) flasks which help to collect the separated compounds


What is the mobile phase composed of in HPLC

polar, protic, or acidic compunds


Explain Size Exclusion Chromatography

SEC uses neutral beads which which cause smaller compounds to elute slower than other compounds


What kind of separations is the SEC beneficial for?

You can use SEC for separating large peptides from smallerpeptides, large polysaccharides from smaller polysaccharides.


Affinity Chromatography can be achieved using these 3 broad methods

1) Large Scale : Column is packed with solid resin, and then lysate is poured through
2) Small Scale: you can miz solid phase with lysate and centrifuge. Then you can collect the solid phase at bottom, which contains proteins.
3) You can use specific antibodies that will bind to protein of interest. Then, a protein linked to a solid bead is dropped in, attaches to your anti body, You then centrifuge.
4) Lastly, magnetic beads can be used to attach to the protein of interest, and then you use a magnet to retrieve your desired product.


What is an affinity tag?

An affinity tag is a small molecular tag added to a protein via molecular recombination. Bacteria produce these tagged protein, and resulting cell lysate can go ahead and be rich in the bacteria.

The DO NOT interfere with any of the protein folding or structure.


Summarize the machine components of gas chromatography

1) Gas Supply
2) Injector
3) column with the liquid stationary phase
4) Detector
5) Recorder


Summarize concept of gas chromatography in general

In gas chromatography, you have a solution filled with different compounds that have different polarities and boiling points and volatility

Then, you have a column with a stationary liquid phase. The liquid you inject in the injector is quickly vaporized and carried by an inert gas such as Helium.

Then, this gas is carried across the column, where based on the volatility of the compounds, they can either hang out with the liquid stationary phase, or continue on wards with the gas to the detector and exit quickly.


In gas chromatography, how does volatility influence the order by which compounds are exited?

More volatile compounds can stay in the gas phase longer, while less volatile compounds "hang out " with the liquid phase in the column.


Gas chromatography is like distillation for small amounts of compounds, but how do you separate large amounts of compounds?

You use fractional distillation!!!


Gas chromatography uses which property of molecules to separate them?

Volatility/boiling point


Name the 3 classes of hydrocarbons that can be referred to calculate whether they have relatively higher/lower boiling points.

1) Small hydrocarbons (1-4) tend to be GASES at room temp
2) Medium Hydrocarbons (5-16) tend to be LIQUID in room temp
3) Large hydrocarbons (17 above) tend to be WAXY SOLIDS at room temperature.


Are more branchy hydrocarbons volatile compared to straight chain hydrocarbons?



What is the one force you know about that can SIGNIFICANTLY affect boiling point

Hydrogen bonds!


What is the formal definition of distillation?

Raising the temperature of a liquid until it can overcome the bonds that keep it a liquid.


What is difference between simple vs. fractional distillation

1)Simple distillation can be used for liquids that have fairly different boiling points, and are used for simple processes, such as water sitillation
2) Fractional distillation can be used for products with much more closely related boiling points. They utilize a copper sponge that can help create multiple cycles of vaporization , in which eventually the lowest BP vapor comes out and then turns back into liquid.