Column Part 1

Question 1

Draw the structure of Bixin

Answer 1

Refer to notes

Question 2

Draw the structure of methyl bixin

Answer 2

refer to ntoes

Question 3

Draw the structure of norobixin

Answer 3

refer to notes

Question 4

What are the two equations relating frequency of light, speed of light, wavelength of light, and energy to one another?

Answer 4

refer to notes

Question 5

How are energy, frequency and wavelength related to each other?

Answer 5

Increasing frequency and increasing energy are correlated with decreasing wavelength

Question 6

What does absorption at UV and visible wavelengths do to electrons?

Answer 6

Promotes them from HOMO to LUMO

Question 7

What reduces the HOMO to LUMO gap?

Answer 7

Extended conjugation lowers the gap between the ground adn the exceed state. this lowers the frequency = absorption at longer wavelength

Question 8

Observed color is complementary to the color of the wavelength absorbed. Draw the color wheel and show the direct that wavelength increases in

Answer 8

Refer ot notes

Question 9

What are the four types of chromatographic methods?

Answer 9

1. TLC - Thin Layer Chromatography
2. LC – Liquid Chromatography (SP- Silica gel or Alumina; MP – a
   liquid)
3. HPLC - High Performance Liquid Chromatography (utilizes high
   pressure exerted by mechanical pumps to force the mobile phase
   through a very small diameter column packing that contains the
   stationary phase).
4. GC - Gas Chromatography (MP – a gas)

Question 10

What are the advantages to chromatography?

Answer 10

1. Simple, economical method for separation of components in a mixture
2. Helps in following the progress of a chemical reaction
3. No restriction on sample type - organic, inorganic, biological, or medical
4. High Sensitivity – Detection of μg amounts or less (10-6 g)
5. Helps in determining the effectiveness of a purification.
6. Helps to determine the conditions for macroscopic separations
   (Column Chromatography)

Question 11

What is chromatography or “color writing”

Answer 11

Routinely used as a qualitative analytical tool

Identification of Unknowns by comparison with known
reference samples

Question 12

Draw the table differentiating stationary phase from mobile phase in chromatography

Answer 12

refer to notes

Question 13

What are examples of absorbents used in the stationary phase?

Answer 13

1. Silica gel (SiO2): Most commonly used, inexpensive stationary phase
2. Aluminum oxide (Al2O3)

Question 14

Silica gel is an extended (1) network of tetrahedral Is atoms bridged by O atoms, terminating in very (2) (3) groups, creating a very (2) surface.

Answer 14

(1) covalent
(2) polar
(3) silanol (Si-OH)

Question 15

What is the composition of a TLC plate

Answer 15

250 um silica gel impregnated with a fluorescent indicator, on a plastic backing

Question 16

Draw the silica gel structure

Answer 16

refer ot ntoes

Question 17

What compound is added to the silica gel to help it bind to a plate?

Answer 17

CaSO4

Question 18

What is the compound added to the silica gel to help it fluoresce?

Answer 18

ZnS which absorbs at 254 nm

Question 19

How will molecules interact with the stationary phase of the TLC plate?

Answer 19

Highly polar molecules will interact strongly with the polar Si-
OH bonds in the silica gel adsorbent – resulting in slow
movement up the TLC plate.

Weakly polar molecules are held less tightly than the polar
species on the silica gel adsorbent – resulting in quicker
movement up the TLC plate

Question 20

How do you calculate the rf value?

Answer 20

Rf = (distance traveled by compound or solute)/ (distance traveled by solvent or eluent)

Question 21

How do rf values correspond to the polarity of a compound?

Answer 21

More polar compounds have smaller rf values, and travel shorter distances on the TLC plate

less polar compounds have larger Rf values and travel a longer distance on the TLC plate

Question 22

Always spot on the ____ side of the TLC plate

Answer 22

rough side

the smooth side is the plastic backing

Question 23

Draft he schematic for a developing chamber to run TLC plate

Answer 23

Refer ot notes

Question 24

Draw the flow chart

Answer 24

refer to notes

Question 25

What are the three eluting solvents tested?

Answer 25

Ch2Cl2 3% Ethanol in CH2Cl2 10% Ethanol in CH2Cl2

Question 26

What is the hazard associated with DCM

Answer 26

Carcinogenic compound

Question 27

What is the most important safety precaution taken in this lab?

Answer 27

Double gloving

Question 28

What is the waste disposal procedure for this experiment? Annatto seeds, Buchner funnel filter paper, vacuum filter flask + Buchner funnel + 50 mL beaker, TLC used capillary tubes

Answer 28

Annatto seeds (waste) – biohazard waste box * Buchner funnel filter paper - biohazard waste box. * Vacuum filter flask, Buchner funnel & 50 mL beaker, 100ml RBF, ll 125mL and 250 mL erl. flask, grad. cylinders, powder funnel, pyres funnel – to be rinsed with acetone and emptied into “CHO HALOGENATED & Acetone Rinsings” waste container. * Used TLC capillary tubes – Red Sharps container. All of the developing solvents should go into “CHO HALOGENATED & Acetone Rinsings” waste container.

Question 29

What is the solvent determined to be most ideal for column chromatography?

Answer 29

3% EtOH in DCM

Question 30

Should you wet the filter paper with water in this experiment?

Answer 30

no

Question 31

should the filter paper be changed after every filtration step?

Answer 31

yes

Question 32

Since we are working with DCM, what is an important consideration to keep in mind when working with the vacuum?

Answer 32

Do not keep it on for too long

Question 33

What is the application of boxing extract?

Answer 33

The extract, which is orange-red, is used as a natural colorant in many foods such as cheese and snack foods. It is currently an unregulated color additive and is estimated to be one of the most highly used food colorants in the US food supply.

Question 34

The annatto extract that is used as a food colorant contains not only bixin, but many other carotenoids including methyl bixin and norbixin. What are carotenoids and give two examples of common carotenoids.

Answer 34

The carotenoids are one group of highly colored organic molecules. One familiar example of a carotenoid is β-carotene. The absorption of blue light at wavelengths of 453 and 483 nm leads to its orange color. Lycopene absorbs at a slightly longer wavelength of 505 nm in the green region. The absorption of green light leads to its characteristic red color. These two compounds, along with bixin and its derivatives, all have 11 double bonds in conjugation

Question 35

What are the functional groups present in bixin, methyl bixin, and norobixin? which is the most to lest polar?

Answer 35

Bixin has a carboxylic group on one side and a methyl ester on the other. In methyl bixin, both groups are methyl esters whereas in norbixin they are both carboxylic acids. These differences give the molecules different polarities which enable us to separate them by column chromatography. Methyl bixin is the least polar and norobixin is the most polar.

Question 36

Describe the general procedure for this expeirment

Answer 36

1. complete all the extractions 2. TLC plate in each of the three solvents to determine the best solvent 3. rotovap your annatto extract

Question 37

What would happen if the Rf value is too big or if the Rf value is too small.

Answer 37

If the Rf of bixin is too high, the compound will move off the column very quickly which will not allow separation to occur. However, if the Rf is very low, it will be difficult to get the compound to elute off the column. In the optimal separation, the bixin should move off the baseline (Rf between 0.25 to 0.5) and show significant distance from all other compounds.

Question 38

If your gloves become damaged, grossly soiled, or contaminated:

Answer 38

1. Remove the gloves 2. Wash hands for 20 seconds with soap and warm water 3. Replace with new pairs of gloves