Extraction and Recrystallization of Caffeine from Tea

Question 1

Caffeine belongs to a group of natural products called _________. From the structure we can classify it as belonging to _______. It is called ___________.

Answer 1

(a) alkaloid
(b) amide
(c) methyl xanthine

Question 2

Caffeine is ( basic or acidic ) due to ________ atoms will react with acids converting the nitrogen atoms to a _______ thus increasing its _________ in water

Answer 2

(a) basic
(b) nitrogen
(c) cation
(d) solubility

Question 3

If caffeine is in a basic environment such as in sodium carbonate, it will ___________

Answer 3

remain as a free base

Question 3

If caffeine is in __________ form, it is ________ and so less soluble in water but more soluble in the ___________ which is _____________

Answer 3

(a) neutral form
(b) less polar
(c) extracting solvent
(d) ethyl acetate

Question 4

Extracting slovent must be/have: (3)

Answer 4

(1) immiscible w/ the solution to be extracted
(2) good solubility of the target compound
(3) volatile

Question 5

TRUE/FALSE
Ethyl acetate is immiscible in water

Answer 5

TRUE

Question 6

TRUE/FALSE
Caffeine is not soluble in ethyl acetate

Answer 6

FALSE. very soluble in ethyl acetate

Question 7

Ethyl acetate is evaporated at ________ to yield the ____________

Answer 7

(a) room temperature
(b) crude caffeine

Question 8

It is needed to break the emulsion and allow separation of the organic and aqueous layer

Answer 8

Centrifugation

Question 9

What is the purpose of centrifugation

Answer 9

to break the emulsion and allow separation of the organic and aqueous layers.

Question 9

Refers to the drying agent used to remove moisture from the ethyl acetate solution

Answer 9

Anhydrous Calcium chloride (CaCl2)

Question 10

TRUE/FALSE
We should not add too much drying agent

Answer 10

TRUE

Question 11

What will happen if we add too much drying agent

Answer 11

the ethyl acetate will also be absorbed and the weight of caffeine crystal will decrease

Question 12

The ethyl solvent is removed by _________ leaving behind the _____________

Answer 12

(a) evaporation
(b) caffeine crystal

Question 13

Refers to a colorless, needle-like crystal

Answer 13

Caffeine

Question 14

TRUE/FALSE
We cannot use methanol as extracting solvent

Answer 14

TRUE

Question 15

Why can’t we use methanol as the extracting solvent

Answer 15

because it is miscible in water hence we cannot produce two layers

Question 16

What must be done to determine which layer is ethyl acetate layer

Answer 16

add a few drops of it (methanol) and observe to which layer it is miscible

Question 17

These are toxic substances such as chloroform, dichloromethane, and carbon tetrachloride.

Answer 17

Chlorinated solvents

Question 18

What are the (2) other alternative methods which avoid the use of chlorinated solvents

Answer 18

(1) Supercritical carbon dioxide extraction
(2) Extraction by other organic solvents such as ethyl acetate

Question 19

Formula in getting the percent yield of recrystallized from crude caffeine

Answer 19

% yield = (wt. purified/wt. crude) x 100

Question 20

TRUE/FALSE
Caffeine is soluble in both methanol and methylene chloride but it cannot be use to extract the caffeine from the aqueous portion.

Answer 20

TRUE

Question 21

In the experiment, what is used as the recrystallizing solvent

Answer 21

hot ethanol

Question 22

why do wen need to heat the recrystallizing solvent?

Answer 22

when recrystallizing solvent is heated, the kinetic energy required to dissolve the compound is reduced. The less solvent is required to dissolve the compound, the solution becomes more saturated, making it faster for crystals to form.

Question 23

what physical property would explain why one layer is on top. of the other?

Answer 23

Density

Question 24

what is tge purpose of adding sodium carbonate to the tea solution

Answer 24

to ensure that the tannins ,present in tea leaves, remains water soluble and that the caffeine will be present as free base

Question 25

dichloromethane is generally a nasty stuff. what could be used to replace halogenated solvents in this extraction procedure?

Answer 25

Ethyl acetate