Term
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Definition
| It is defined as the separation of a mixture of two or more different compounds by distribution between two phases, one of which is stationary and one of which is moving. |
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Term
| What is column chromatography? What is it based on? |
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Definition
It is based on the difference between absorptivity of a compound onto the solid stationary phase and its solubility in the liquid mobile phase.
Ie if the substance has a high affinity for the stationary phase it will remain there (or near the top) and if it has a low affinity for the stationary phase / is soluble in liquid than will move through the column quickly. |
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Term
| What is silica gel a form of? |
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Definition
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Term
| Why is Silica Gel good for the stationary phase in chromatography? |
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Definition
| Because the silicon in silica gel terminates in a hydroxyl group...This forms a huge polymeric structure with a surface that comprises of many hydroxyl groups. This makes it a polar, stationary phase. |
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Term
| How do you calculate the Rf value ? What would a high Rf value mean, converselywhat would a low Rf value mean? |
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Definition
Rf = distance traveled by substance/distance traveled by solvent front
A high Rf (Ie 0.92) would refer to a substance that is very non-polar. Ie that substance moved a 92% of the entire distance the solvent traveled.
A low Rf value (0.10) would refer to a substance that is very polar. IE that substance was only able to move 10% of the entire distance the solvent traveled. |
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Term
| What are the analgesic drugs used in Part D of experiment 3? |
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Definition
Acetylsalicylic Acid
Acetaminophen
Caffeine
Codeine |
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Term
| What are the types of plant pigments possible to be seen? |
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Definition
Green chlorins --> Chlorophyll A and B (B = more polar than A)
Yellow-Orange Carotenoids --> Two carotenes and three xanthophylls (Xanthophylls are more polar than carotenes) |
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Term
| What is the solvent used in Experiment #3, part A? Separation of ink pigment by microscale column chromatography |
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Definition
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Term
What is the solvent used in Experiment #3, part B?
Separation and Isolation of ink pigment using TLC |
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Definition
| 9:1 95% Ethanol: Acetic Acid |
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Term
| What type of beaker is used in Experiment 3, A-C, to create the development chambers? |
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Definition
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Term
What is the solvent used in Experiment #3, Part C?
Separation of plant pigment using TLC |
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Definition
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Term
What is the solved used in Experiment #3, Part D?
Analysis of Analgesics by TLC |
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Definition
| 25:1 Ethyl acetate: Acetic Acid |
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Term
| What is the difference between the development order for column chromatography and TLC plates? |
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Definition
In column chromatography the most polar molecules remain at the top of the column (because it develops from the top down) whereas with TLC plates it is reverse, the most polar molecules are at the bottom.
Basically, the most polar molecules remain nearest to the point of application of the sample. |
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Term
| What type of functional group on the stationary phase enables chromatography to work? |
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Definition
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Term
| Which is more polar, chlorophyll A or B? |
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Definition
| Clorophyll B is more polar than A |
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Term
| Which is more polar, the Xanthophylls (yellows) or the carotenes (alpha and beta, yellow/orange) |
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Definition
| The xanthophylls are more polar than alpha and beta carotene. |
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Term
| What does the mixture in Experiment #4 contain? |
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Definition
| Contains benzoic acid and Benzil. They are dissolved in dichloromethane. |
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Term
| How are acidic organic compounds separated out of mixtures? |
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Definition
Acidic Organic Compounds are compounds that are insoluble in water and react with acqueous solutions of bases to form their respective conjugate bases (carboxylates) which are highly soluble in water. The conjugate bases are charged anion species.
Example: Benzoic Acid + NaOH ---> Sodium Benzoate + H2O |
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Term
| In experiment #4, what is benzoic acid reacted with to create its conjugate? What is the name of the conjugate? |
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Definition
| Benzoic Acid reacts with NaOH to create the conjugate base Sodium Benzoate. |
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Term
| What are basic organic compounds reacted with to make them soluble in water? |
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Definition
| Basic organic compounds (such as amines) react with acqueous solutions of acids (HCl) to form the corresponding conjugate acid. Creates cation molecule. |
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Term
| What are neutral organic compounds reacted with? |
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Definition
| They are more soluble in organic solvents than both acidic or basic aqueous solvents. |
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Term
| Explain the two solvent recrystallization technique? |
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Definition
Two miscible solvents are chosen:
Solvent A: In which the solid is very soluble at all temperatures
Solvent B: Solvent in which the solid is insoluble at all temperatures.
The solid is dissolved in a minimum amount of Solvent A, then hot solvent B is added drop wise until the solution becomes cloudy. Next, a few drops of Solvent A is added to just clear the cloudiness. Then you cool the solution so crystals can form. |
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Term
| What do you add to the yellow organic layer (flask #3) to dry to organic layer? |
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Definition
| You add a spatula full of sodium sulphate into flask #3 which forms a hydrate with residual water that is prsent. This results in drying of the organic layer. |
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Term
| How do you isolate benzoic acid from the dichloromethane mixture that also contains benzil? |
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Definition
| First you add a small amount of NaOH (a base) to the mixture in a seperatory funnel and shake it, which converts benzoic acid into sodium benzoate (dissolved in the water) and leaves benzil in the dichloromethane. You then drain off these into two separate beakers. To return the sodium benzoate to the original compound, you treat it with a small amount of HCl. Then, to crystallize it you use the two solvent crystallization method. |
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