Lab Final

Question 1

Recrystallization and Melting Point - Lab 1

What is the main method of purification in this lab?

Answer 1

recrystallization

Question 2

Recrystallization and Melting Point - Lab 1

Recrystallization works best when a compound has high solubility in a solvent at what level of temperature?

Answer 2

high

and vice versa for low

Question 3

Recrystallization and Melting Point - Lab 1

When are undesired impurities removed from the compound?

Answer 3

When they are insoluble in a particular solvent at a particular temperature.

These two factors are crutial for pure results.

Question 4

Recrystallization and Melting Point - Lab 1

When using the Mel-Temp Apparatus, how many degrees should you start below the literature melting point (expected) for the compound?

Answer 4

10ºC or lower

Question 5

Recrystallization and Melting Point - Lab 1

Why do we add hot water to the unknown compound at the start of the experiment?

Answer 5

To dissolve the compound to allow for the recrystallization to start.

Impurities will be left floating in the water.

Question 6

Recrystallization and Melting Point - Lab 1

What is the mode of filtration for this experiment?

Answer 6

Vacuum filtration through a Büchner funnel

Question 7

Extraction of Caffeine from Tea Bags - Lab 2

What form of the bases family is caffeine apart of? What distinguishes this group?

Answer 7

Purines; They have a a double ring structure

Question 8

Extraction of Caffeine from Tea Bags - Lab 2

Even though caffeine is soluble in water, it is even MORE soluble in what organic solvent used in this experiment?

Answer 8

methylene chloride

Question 9

Extraction of Caffeine from Tea Bags - Lab 2

What technique is introduced in this experiment?

Answer 9

liquid-liquid extraction

Question 10

Extraction of Caffeine from Tea Bags - Lab 2

Why are the tea leaves boiled in water for the extraction? Why is this effective?

Answer 10

To break up the cellulose and release the caffeine in the form of a liquid.
This is effective because cellulose is not easily broken down by hot water due to it’s intra and intermolecular H-bonding.

Question 11

Extraction of Caffeine from Tea Bags - Lab 2

Why did we HAVE to cool the tea solution down to room temperature before adding the methylene chloride?

Answer 11

Because methylene chloride has a low temperature of evaporation, so if it were to evaporate out, not all of the caffeine would be extracted.

Question 12

Extraction of Caffeine from Tea Bags - Lab 2

At the end of using the seperatory funnel, what does the bottom, organic layer consist of in this experiment?

Answer 12

Methylene chloride and the dissolved caffeine

Question 13

Extraction of Caffeine from Tea Bags - Lab 2

Why is calcium chloride added to the collected organic extract?

Answer 13

To absorb any residual water

Question 14

Extraction of Caffeine from Tea Bags - Lab 2

What are two other common drying agents?

Answer 14

• silica gel
• aluminum oxide

Question 15

Acid-Base Extraction - Lab 3

What are the three acidic, basic, and neutral organic compounds in this experiment?

Answer 15

Acidic = carboxylic acid
Basic = amine
Neutral = aldehyde

Question 16

Acid-Base Extraction - Lab 3

With what inorganic bases can carboxylic acids react with to produce a sodium salt?

Answer 16

NaHCO3 or NaOH

Question 17

Acid-Base Extraction - Lab 3

With what inorganic acid can amide react with to produce an ammonium salt?

Answer 17

HCl

Question 18

Acid-Base Extraction - Lab 3

What happens when neutral compounds are subjected to inorganic acids and bases?

Answer 18

They will not undergo and acid-base reaction

Question 19

Acid-Base Extraction - Lab 3

Reaction Tree: After 5mL of HCl is added to the three-component mixture, what is then done to produce the Component 1 (4-Chloroanaline)?

Answer 19

Basify with NaHCO3 and filter

Question 20

Reaction Tree: After 5mL of HCl is added to the three-component mixture, what is produced before 5mL of saturated NaHCO3 is added?

Answer 20

Organic Layer A

Question 21

Acid-Base Extraction - Lab 3

Reaction Tree: After 5mL of saturated NaHCO3 is added to organic layer A, NaHCO3 wash is created, what must be done next to produce Component 2 (benzoic acid)? What is the other product of adding NaHCO3 to the organic layer A?

Answer 21

The combined aqueous layers must be acidified with HCl and then vacuum filtrated.

Organic layers B and C are also created.

Question 22

IR and NMR Spectroscopy - Lab 5

The degree of unsaturation (DOU) formula is:
DOU = [C(2C+2)-C(H)]/2

After plugging in the number of carbon and hydrogen atoms, what does the DOU value tell us?

Answer 22

It will tell us the number of pi bonds and/or rings.

Ex.
4 DOU = 2 pi bonds and 2 rings

Question 23

IR and NMR Spectroscopy - Lab 5

What is the 1H NMR frequency of an O-H and N-H bond?

Answer 23

3400 cm-1

Question 24

IR and NMR Spectroscopy - Lab 5

What is the 1H NMR frequency of a C=O bond?

Answer 24

1700 cm-1

Question 25

IR and NMR Spectroscopy - Lab 5

What is the 1H NMR frequency of a C-H (sp3) bond?

Answer 25

3000-2850 cm-1

Question 26

TLC and Column Chromatography - Lab 6

Between fluorene and fluorenone, which is the polar compound?

Answer 26

fluorenone

Question 27

TLC and Column Chromatography - Lab 6

How do you calculate Rf values?

Answer 27

You take the distance traveled of the compound spot and divide it by the distance traveled by the solvent.

Rf = spot distance/total solvent distance

Question 28

TLC and Column Chromatography - Lab 6

How do we determine the ideal solvent system based on Rf values?

Answer 28

If the Rf value is around 0.25-0.35 and at least 0.2 Rf differnce from other compounds.