What is a technique used to purify organic solids?
When an organic chemist conducts a recrystallization, he chooses a solvent that will what?
completely dissolve both the desired compound and any other organic impurities when that solvent is at BP
In addition to solubility at boiling temperature requirement of the solvent in recrystallization, the desired compound must also be what?
insoluble in the chosen solvent at cold temperatures, and the organic impurities must remain soluble when solution is cooled.
Insoluble impurities are typically removed by what in recrystallization?
hot gravity filtration
What do the seed crystals do?
they serve as nucleation sites where more molecules of the desired compound deposit themselves in layers
what is the purpose of the icebath during recrystallization?
it maximizes crystal formation
in recrystallization, by what method are the crystals collected?
What is the purpose of a hot gravity filtration?
so it doesn't crystallize and to remove impurities rather than to isolate solids
Why is it good to use the stemless funnel for hot gravity filtration?
it prevents what is being filtered from cooling and forming crystals too early
What is a ligroin?
a non-polar solvent. colorless and flammable liquid.
Why is HCl used instead of plain deionized water in p-phenetidine is dissolved in HCl?
because it forms a salt by protonating the ammonia group, making it easy to dissolve
What is the purpose of the sodium acetate solution in the amide synthesis of acetophenetidin?
we need a base to take away an H so that acetic anhydride can complete the reaction. So it buffers rxn mix
What is the phenomena that occurs when a liquid is heated above its BP in a clean, smooth container.
Why should you always use a boiling stone or a boiling stick whenever you heat any liquid in the lab?
to avoid bumping
How is the melting point of a pure substance defines as?
the temp at which the solid phase is in equilibrium with the liquid phase.
In an IR, what can be found between 1550-1900?
In an IR, what can be found in 2000-2300?
c (triple bond) c
c (triple bond) n
around 3000, what can be found in IR?
C (Triple bond) CH
[2*C – H – hal + N +2]/2
How does extraction work in brewing a cup of coffee?
the hot water extracts organic compounds from ground coffee beans
Why is CO2 used as a solvent in solid liquid extractions?
it offers a greener alternative, readily available, nonflammable, nontoxic and safe for enviornment. Ease of removal of solvent at end of procedure (converts into a gas and boils away) "carbon neutral"
What are the criteria for a liquid-liquid extraction to be successful?
-the 2 solvents chosen for extraction must be immiscible
-the compounds to be extracted must have different affinities for the two solvents.
what is a strong enough base to deprotonate a carboxylic acid?
what is not reactive with basse, so it remains unchanged in the organic phace?
a neutral organic molecule
what happens with a phenol and a NaHCO3?
What do we use to wash an organic layer to remove the majority of dissolved water?
What absorbs the water that is dissolved in the organic solvent?
what is the drying agent removed by in extraction?
decanting or by gravity filtration
is hexane and water miscible?
no, hexane would be top layer
is methylene chloride and water miscible?
no water will be top layer
is ethanol and water miscible?
is ether and water miscible?
no, ether would be top layer
Explain why phenol is much more acidic than cyclohexanol.
conjugate base of cyclohexanol is stronger cus the neg charge on the O atom is delocalized, so phenol is a stronger acid than cyclohexanol
What is the difference between extracting and washing?
extraction is selectively removing a compound of interest from a mixture using a solvent. Washing is removing unwanted compounds from a mixture using a solvent.
WHat is it called when tiny droplets of one liquid become suspended in the other?
Essential oils are often isolated from their plant sources using a technique called what?
Why is it important to soak the cloves in water for several min prior to beginning the distillation?
it will allow water to penetrate the cloves and should allow more eugenol to be isolated
Describe practical reasons behind the direction of the flow of water through the condenser of the disillation apparatus.
vapors formed in heated distillation flask. condenser cools the vapors condensing them back to liquid droplets that flows down the condenser into the cylinder. a filled condenser provides max cooling allowing max recovery of purified liquid during distillation.
What is the purpose of crushing magnesium turnings?
helps to expose fresh metal surface by removing some magnesium oxide on exterior
How does iodine help facilitate the reaction of the magnesium turnings?
cleaning the surface of the Mg metal
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