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CHEM008LA > Experiment 2: Column Chromatography > Flashcards

Experiment 2: Column Chromatography Flashcards

1
Q

What will be done in this lab mainly?

A

We will isolate and separarte B-carotene and chlorophylls A and B from spinach leaves.

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2
Q

Define Natural Products

A

Molecules that are made by nature and are naturally occurring in our environment.

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3
Q

What is the compound made by poison ivy?

A

Urushiol

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4
Q

What is the toxin that can be made from pufferfish?

A

Tetrodotoxin

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5
Q

Are chlorophylls and B-carotene natural products?

A

Yes, they are.

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6
Q

What is the significance of chlorophyll?

A

They are responsible for the plant’s green color and its main role is to absorb light energy to turn water and carbon dioxide into chemical energy, a process called photosynthesis.

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7
Q

What is the benefit of chlorophyll for humans?

A

It acts as a source of magnesium that’s important for heart and muscle health.

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8
Q

What does the chemical structure of chlorophyll resemble?

A

Resembles the structure of hemoglobin, a molecule that is responsible for transporting oxygen in the blood.

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9
Q

What is the major difference between hemoglobin and chlorophyll?

A

The central metal atom: magnesium in chlorophyll and iron in hemoglobin.

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10
Q

What is the significance of the human body being able to swap magnesium for iron?

A

From that, you are able to turn chlorophylls into hemoglobin.

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11
Q

What are some significant things to note about B-Carotene?

A

It is the compound that gives carrots their orange color; additionally, it is an anti-aging molecule, fights oxidative stress and cognitive decline. It is also a precursor to vitamin A.

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12
Q

What can B-Carotene be found in?

A

Kale, Asparagus, Spinach, Mangoes, Melons

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13
Q

Define Chromatography

A

General term applied to several separation methods that utilize the physical properties of solutes in a mixture and the solvents used to separate them.

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14
Q

Define Thin Layer Chromatography

A

An analytical method used to determine whether a substance is pure or a mixture of compounds. Two phases are used for separation: the mobile and stationary phase.

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15
Q

Define Stationary Phase

A

Made of adsorbent (able to absorb other molecules) material that competes with the mobile phase for the attraction of individual solutes in a mixture.

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16
Q

What does “thin layer” refer to in thin layer chromatography?

A

The use of a thin plate of silica gel that acts as the stationary phase.

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17
Q

Define Mobile Phase

A

The mobile phase is consisted of a solvent or a combination of solvents that vary in polarity.

18
Q

Describe the process that happens in TLC.

A

The molecules are attracted to both the stationary and the mobile phase and will partition between them as the solvent up the stationary phase by capillary action.

19
Q

How is a chromatogram made?

A

Individual solutes travel different rates as they are carried by the solvent. So, the variable rates by which the components travel produce a pattern called a chromatogram.

20
Q

How do extremely polar molecules move in TLC? How about non-polar/less polar substances?

A

Since the silica gel that makes up the stationary phase is polar, polar solutes that have a strong attraction for the stationary phase will move the shortest distance.

On the other hand, molecules that have the least affinity for the stationary phase will move the furthest.

21
Q

Define Retention Factor

A

The distance the components of a mixture move on chromatography paper compared to the distance the solvent moves.

22
Q

Where do the Rf values fall and what do they indicate? Also, what is the formula for Rf?

A

They fall between 0-1. A value of 0 indicates that the component did not move with the solvent (mobile phase) and a value of 1 indicates that the component mostly interacted with the mobile phase and was not retained by the stationary phase.

Rf= distance to center of spot/distance to solvent front

23
Q

What is the relationship between polarity and Rf values?

A

They have an inverse relationship.

24
Q

What is the most common technique for purifying mixtures of compound in O-chem?

A

Column chromatography

25
Q

How does column chromatography compare to TLC?

A

Column chromatography has the same basic principles followed in TLC. TLC is mainly used to analyze the purity of the sample but the plates are too small to conduct purifications. BOTH involve their silica gel as the stationary phase, to which the mixture is added. The solvent or ELUENT is added to the silica gel to elute the compounds, resulting in separation.

26
Q

What is the major difference between TLC and column chromatography?

A

In TLC, the compound is introduced near the BOTTOM of the TLC plate, the solvent is at the BOTTOM, which flows UP the TLC plate. In column chromatography, the compound is loaded at the top of the column, the solvent is added to the top, which flows DOWN the column.

27
Q

How is a column set up for column chromatography?

A

A vertical glass unit is used to hold the silica gel. Silica should be tightly packed and equilibrated by passing solvent through it. A small layer of sand is added to the top of the silica gel to prevent it from being disturbed when introducing the sample and eluent to the column. From there, the eluent exiting the column is collected into the test tubes that will be analyzed by TLC.

28
Q

What is the range of visible light?

A

400nm to 700nm (700 being red and 400 being violet)

29
Q

What is the relationship between wavelength and energy?

A

Inverse

30
Q

What is a shared feature between B-Carotene, chlorophylls A & B, and hemoglobin?

A

There are a large # of alternating single and double bonds known as conjugation.

31
Q

What is the process of us seeing complementary colors?

A

When white light is shined onto a colored substance, some of the light is absorbed. The remainder of the light is unabsorbed light known as the complementary color.

32
Q

What is the relationship between the # of pi bonds arranged in conjugation and the wavelength of light absorbed?

A

Direct

33
Q

What must a substance have to be considered a conjugated molecule?

A

At least 2 double bonds.

34
Q

What is the technique of rotary evaporation used for?

A

To remove solvent quickly. The concept behind it is to lower the pressure above the liquid to allow it to evaporate well below its boiling point.

35
Q

What are the components of a rotovap?

A

Condenser-Solvent Reservoir-Vacuum Pump-Bump Trap-Mechanical Rotating Unit-Water Bath. CSV-BMW

36
Q

What is the function of the Vacuum Pump?

A

Lowers the pressure inside of the system, which lowers the boiling point of the solvent(s) being evaporated.

37
Q

What is the function of the Water Bath?

A

Heating the sample to facilitate evaporation.

38
Q

What is the function of the Mechanical Rotating Unit?

A

Spinning the flask to ensure heating of the sample; additionally, it helps form a thin film of the solvent around the flask, increasing the surface area for evaporation.

39
Q

What is the function of the Bump Trap?

A

With rotovapping, your intention is to get the solvent into the solvent reservoir, leaving the compound of interest behind. When the pressure is too low, temperature is too high, flask is too full, or if the solution is not fully homogenous, the sample can “bump” directly into the solvent reservoir. THE BUMP TRAP IS designed to trap the “bumped” content.

40
Q

What is the function of the condenser?

A

Contains a cold surface that condenses the solvent vapors back into a liquid; this is to prevent harmful organic solvents from entering the pump and the lab.

41
Q

What is the function of te solvent reservoir?

A

To collect the liquid condensate from the condenser.

CHEM008LA (3 decks)

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