What is a technique used to purify organic solids?
recrystallization
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?
vacuum filtration
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.
superheating
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?
C=O C=N C=C
In an IR, what can be found in 2000-2300?
c (triple bond) cc (triple bond) n
around 3000, what can be found in IR?
N-HO-H C=CH C (Triple bond) CH
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”
How does extraction work in brewing a cup of coffee?
the hot water extracts organic compounds from ground coffee beans
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?
hydroxide ion
what is not reactive with basse, so it remains unchanged in the organic phace?
a neutral organic molecule
What do we use to wash an organic layer to remove the majority of dissolved water?
brine
What absorbs the water that is dissolved in the organic solvent?
anhydrous salt
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?
yes
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?
emulsion
Essential oils are often isolated from their plant sources using a technique called what?
steam distillation
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
What is an example of a qualitative test for an alkene or alkyne?
rxn of the unknown compound with bromine, if alkene or alkyne is present in the molecule, the reddish-brown of Br will disappear.
What are the drawbacks to the qualitative approach?
many tests are tricky to run and may use hazardous reagents-the tests do not identify the actual molecule, just presence of particular functional group
In addition to qualitative tests, chemist often made what in order to identify the original unknown?
derivatives of compounds
What kind of information does IR spectroscopy give us?
about what functional groups are present in the molecule.
What kind of information does NMR spectroscopy give us?
about the structure and bonding in a molecule.
How do chemists determine the molecular formula of a compound?
obtain an elemental analysis of the compound
Can IR spectroscopy be used to distinguish 2-pentanone from 2-hexanone?
No, because IR is used to distinguish b/w functional group. Both structures have same functional group, so you will then have to distinguish by their Hydrogens in HNMR. 2-pentanone will have 4 signals and 2-hexanone will have 5.
What is a polymer?
a large molecule that is made up from many smaller molecules called monomers
How are polymers formed?
through synthetic process called polymerization where monomers are chemically linked together.
what is a polymer of glucose?
cellulose
What is an example of a synthetic polymer? Natural?
S: polystyrene
N: cotton
What are the 3 different polymerizations seen in lab?
Condensation, Chain addition, Slime
What form of polymerization is this? Two monomers react to form a larger unit while a small molecule is eliminated.
condensation
What are classic examples of condensation polymers?
polyamides and polyesters
what kind of polymerization is Nylon-10,6 produced?
condensation polymerization
Why do we use a diacid chloride in the making polymers condensation experiment rather than dicarboxylic acid that is typically used industrially?
because the acid halide is more reactive.
what is added to the polymerization rxn mixture to neutralize the HCl released each time a new amide bond is formed?
NaOH
What method of polymerization is used to make polystyrene?
chain addition polymerization
What does a chain addition polymerization involve?
the use of an initiator that forms a reactive species
What is the initiator in our polystyrene synthesis?
Benzoyl peroxide
What does benzoyl peroxide generate in chain addition polymerization of styrene?
radicals
What does the radicals generated by the benzoyl peroxide in chain addition polymerization do?
they react with styrene monomer to begin the chain addition process.
How does chain addition differ from condensation polymerization?
a chain addition involves a vinyl-type monomer.-polymers that are formed by chain addition from vinyl-type monomers have a simple hydrocarbon backbone -emperical formula of chain addition polymer is identical to that of the monomer.
What is the simplest vinyl-type monomer?
ethylene
In condensation polymerizations, what are the functional groups part of?
polymer backbone and are formed as monomer units link together.
How is the empirical formula in a condensation polymerization?
the formulas of the monomer and polymer are different
what is slime?
cross-linked polymer
how are the bonds in the cross-links b/w the borate ion and alcohol functional groups of PVA in slime?
weak
monomer
repeating units that serve as the building blocks of a polymer.
repeating unit
group of atoms derived from a monomer and repeats throughout a polymer.
condensation polymerization
2 monomers react to form a larger unit while a small molecule, like H2O or HCl, is eliminated.
cross-linked polymer
polymer in which long-chain molecules are attached to each otherCan be covalent or ionic
Why can’t we use vinyl alcohol in polymerization?
it almost exclusively exists in its tautomeric form, acetylaldehyde.
How is the solubility of polystyrene in acetone? toluene? ethanol?
semi-soluble-nothing -soluble
Electrophilic aromatic substitution rxns are important way for what?
to allow a functional group to be placed on an aromatic ring.
What is an example of an EAS rxn?
Friedel-Crafts acylation
What has been referred to as a “superaromatic” molecule?
Ferrocene
What is a term that refers to techniques for separating, analyzing, and identifying compounds?
chromatography
What are the 4 types of chromatography?
column-TLC -GC -HPLC
what is the mobile phase?
gas or liquid phase
what is the stationary phase?
a solid support that contains an adsorbent
what are bands?
areas of concentration
If a component has a greater affinity for the stationary phase, it will
travel more slowly.
What are the basic steps of chromatography? –
a sample mixture is placed in the mobile phase.-it is carried by mobile phase thru stationary phase. -components pass thru stationary phase as bands and they move at diff. rates depending on interaction w/ stationary phase.
For column and thin layer chromatography, what is the adsorbent for the stationary phase?
silica gel or alumina
silica gel and alumina have what?
many sites for H bonding
in column and thin layer chromatography, what compounds tend to adsorb more readily to the stationary phase?
polar
In both column and thin layer chromatography, what is the solvent used for the mobile phase called?
eluent
True/False, an eluent can vary from very polar to less polar.
True
What is a developing chamber?
a jar with a lid or a beaker with a watch glass cover
on the TLC plate the sample components are separated on what phase?
stationary
what is the solvent front?
leading edge of solvent
What is the Rf value?
a ratio from 0 to 1.
equation for Rf?
(distance from origin to center of the spot)/(distance from origin to solvent front)
The Rf values for polar compounds are? for nonpolar compounds?
smaller-closer to 1
what interacts more strongly with the stationary phase?
polar compounds
Why is it important to keep the sample as concentrated as possible in column chromatography?
so that the entire sample enters column in compact of a band as possible.
How would Rf values change if a more polar solvent were used in TLC plate?
would increase for all compounds
Why is it important not to dilute the initial sample before it has been loaded onto the chromatography column?
if you dilute the sample, it can become a wider band in the column, thus you would be unable to completely separate components
Which compound would you expect to elute first from the column: unreacted ferrocene, acetylferrocene, or diacetylferrocene?
Ferrocine (unreacted) because it is the least polar.
what is the mobile phase used in our TLC experiment?
methylene chloride
What is the purpose of the cotton in the chromatography column?
it will support the packing material and prevent it from clogging the stopcock during elution.
Why should we never allow the volume of solvent in the column to go below the top of the adsorbent while packing the column?
if the top of the adsorbent dries out, channels can form in the packing material that will cause poor separation.
Yield calculation is only accurate if what?
all of a sample is taken on to subsequent steps. always compare moles obtained of product in each step to moles of starting material.
What extract is among the most widely used herbal remedies in the world?
Ginkgo biloba
What is an active component that is found in extracts of Ginkgo biloba?
Ginkgolide B
What did Corey develop the concept of?
retrosynthetic analysis
What are the steps in synthesising benzocaine?
conversion of amine to amide-oxidation of benzylic carbon -hydrolysis of amido group -esterification of carboxylic acid
what is benzocaine?
local anesthetic
what acts as a protecting group during the synthesis?
amine to amide
what do you use to decolorize in the protection step (1st) of multi?
charcoal
Why does the oxidation reaction mixture need to boil gently?
too little heat will keep the rxn from ocurring in a reasonable amout of time, too much heat may cause excessive frothing and possible boil over of rxn mixture
How can you induce crystallization?
by scratching the walls of flask with glass stirring rod
What functional group is seen in an IR spectrum peack at 1700?
C=0
what does a degree of unsaturation of 2 mean?
two double bondsone double bond and one ring two rings one triple bond
what is a more polar solvent we can use instead of ligroin when developing a TLC plate?
ethyl acetate
what is a very polar eluent that can be used besides ligroin in TLC?
water or methanol
in column chromatography, what compound elutes first?
the least polar
x

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