Extraction and Recrystallization of Caffeine from Tea Flashcards
Caffeine belongs to a group of natural products called _________. From the structure we can classify it as belonging to _______. It is called ___________.
(a) alkaloid
(b) amide
(c) methyl xanthine
Caffeine is ( basic or acidic ) due to ________ atoms will react with acids converting the nitrogen atoms to a _______ thus increasing its _________ in water
(a) basic
(b) nitrogen
(c) cation
(d) solubility
If caffeine is in a basic environment such as in sodium carbonate, it will ___________
remain as a free base
If caffeine is in __________ form, it is ________ and so less soluble in water but more soluble in the ___________ which is _____________
(a) neutral form
(b) less polar
(c) extracting solvent
(d) ethyl acetate
Extracting slovent must be/have: (3)
(1) immiscible w/ the solution to be extracted
(2) good solubility of the target compound
(3) volatile
TRUE/FALSE
Ethyl acetate is immiscible in water
TRUE
TRUE/FALSE
Caffeine is not soluble in ethyl acetate
FALSE. very soluble in ethyl acetate
Ethyl acetate is evaporated at ________ to yield the ____________
(a) room temperature
(b) crude caffeine
It is needed to break the emulsion and allow separation of the organic and aqueous layer
Centrifugation
What is the purpose of centrifugation
to break the emulsion and allow separation of the organic and aqueous layers.
Refers to the drying agent used to remove moisture from the ethyl acetate solution
Anhydrous Calcium chloride (CaCl2)
TRUE/FALSE
We should not add too much drying agent
TRUE
What will happen if we add too much drying agent
the ethyl acetate will also be absorbed and the weight of caffeine crystal will decrease
The ethyl solvent is removed by _________ leaving behind the _____________
(a) evaporation
(b) caffeine crystal
Refers to a colorless, needle-like crystal
Caffeine
TRUE/FALSE
We cannot use methanol as extracting solvent
TRUE
Why can’t we use methanol as the extracting solvent
because it is miscible in water hence we cannot produce two layers
What must be done to determine which layer is ethyl acetate layer
add a few drops of it (methanol) and observe to which layer it is miscible
These are toxic substances such as chloroform, dichloromethane, and carbon tetrachloride.
Chlorinated solvents
What are the (2) other alternative methods which avoid the use of chlorinated solvents
(1) Supercritical carbon dioxide extraction
(2) Extraction by other organic solvents such as ethyl acetate
Formula in getting the percent yield of recrystallized from crude caffeine
% yield = (wt. purified/wt. crude) x 100
TRUE/FALSE
Caffeine is soluble in both methanol and methylene chloride but it cannot be use to extract the caffeine from the aqueous portion.
TRUE
In the experiment, what is used as the recrystallizing solvent
hot ethanol
why do wen need to heat the recrystallizing solvent?
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.
what physical property would explain why one layer is on top. of the other?
Density
what is tge purpose of adding sodium carbonate to the tea solution
to ensure that the tannins ,present in tea leaves, remains water soluble and that the caffeine will be present as free base
dichloromethane is generally a nasty stuff. what could be used to replace halogenated solvents in this extraction procedure?
Ethyl acetate
