CHM 2211L – Chemistry – Flashcards
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What is a technique used to purify organic solids?
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recrystallization
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When an organic chemist conducts a recrystallization, he chooses a solvent that will what?
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completely dissolve both the desired compound and any other organic impurities when that solvent is at BP
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In addition to solubility at boiling temperature requirement of the solvent in recrystallization, the desired compound must also be what?
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insoluble in the chosen solvent at cold temperatures, and the organic impurities must remain soluble when solution is cooled.
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Insoluble impurities are typically removed by what in recrystallization?
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hot gravity filtration
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What do the seed crystals do?
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they serve as nucleation sites where more molecules of the desired compound deposit themselves in layers
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what is the purpose of the icebath during recrystallization?
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it maximizes crystal formation
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in recrystallization, by what method are the crystals collected?
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vacuum filtration
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What is the purpose of a hot gravity filtration?
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so it doesn't crystallize and to remove impurities rather than to isolate solids
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Why is it good to use the stemless funnel for hot gravity filtration?
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it prevents what is being filtered from cooling and forming crystals too early
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What is a ligroin?
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a non-polar solvent. colorless and flammable liquid.
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Why is HCl used instead of plain deionized water in p-phenetidine is dissolved in HCl?
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because it forms a salt by protonating the ammonia group, making it easy to dissolve
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What is the purpose of the sodium acetate solution in the amide synthesis of acetophenetidin?
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we need a base to take away an H so that acetic anhydride can complete the reaction. So it buffers rxn mix
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What is the phenomena that occurs when a liquid is heated above its BP in a clean, smooth container.
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superheating
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Why should you always use a boiling stone or a boiling stick whenever you heat any liquid in the lab?
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to avoid bumping
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How is the melting point of a pure substance defines as?
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the temp at which the solid phase is in equilibrium with the liquid phase.
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In an IR, what can be found between 1550-1900?
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C=O C=N C=C
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In an IR, what can be found in 2000-2300?
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c (triple bond) cc (triple bond) n
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around 3000, what can be found in IR?
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N-HO-H C=CH C (Triple bond) CH
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Why is CO2 used as a solvent in solid liquid extractions?
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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"
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How does extraction work in brewing a cup of coffee?
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the hot water extracts organic compounds from ground coffee beans
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What are the criteria for a liquid-liquid extraction to be successful?
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the 2 solvents chosen for extraction must be immiscible-the compounds to be extracted must have different affinities for the two solvents
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what is a strong enough base to deprotonate a carboxylic acid?
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hydroxide ion
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what is not reactive with basse, so it remains unchanged in the organic phace?
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a neutral organic molecule
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What do we use to wash an organic layer to remove the majority of dissolved water?
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brine
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What absorbs the water that is dissolved in the organic solvent?
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anhydrous salt
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what is the drying agent removed by in extraction?
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decanting or by gravity filtration
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is hexane and water miscible?
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no, hexane would be top layer
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is methylene chloride and water miscible?
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no water will be top layer
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is ethanol and water miscible?
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yes
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is ether and water miscible?
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no, ether would be top layer
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Explain why phenol is much more acidic than cyclohexanol.
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conjugate base of cyclohexanol is stronger cus the neg charge on the O atom is delocalized, so phenol is a stronger acid than cyclohexanol
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What is the difference between extracting and washing?
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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.
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What is it called when tiny droplets of one liquid become suspended in the other?
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emulsion
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Essential oils are often isolated from their plant sources using a technique called what?
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steam distillation
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Why is it important to soak the cloves in water for several min prior to beginning the distillation?
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it will allow water to penetrate the cloves and should allow more eugenol to be isolated
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Describe practical reasons behind the direction of the flow of water through the condenser of the disillation apparatus.
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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.
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What is the purpose of crushing magnesium turnings?
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helps to expose fresh metal surface by removing some magnesium oxide on exterior
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How does iodine help facilitate the reaction of the magnesium turnings?
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cleaning the surface of the Mg metal
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What is an example of a qualitative test for an alkene or alkyne?
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rxn of the unknown compound with bromine, if alkene or alkyne is present in the molecule, the reddish-brown of Br will disappear.
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What are the drawbacks to the qualitative approach?
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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
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In addition to qualitative tests, chemist often made what in order to identify the original unknown?
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derivatives of compounds
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What kind of information does IR spectroscopy give us?
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about what functional groups are present in the molecule.
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What kind of information does NMR spectroscopy give us?
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about the structure and bonding in a molecule.
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How do chemists determine the molecular formula of a compound?
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obtain an elemental analysis of the compound
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Can IR spectroscopy be used to distinguish 2-pentanone from 2-hexanone?
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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.
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What is a polymer?
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a large molecule that is made up from many smaller molecules called monomers
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How are polymers formed?
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through synthetic process called polymerization where monomers are chemically linked together.
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what is a polymer of glucose?
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cellulose
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What is an example of a synthetic polymer? Natural?
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S: polystyrene N: cotton
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What are the 3 different polymerizations seen in lab?
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Condensation, Chain addition, Slime
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What form of polymerization is this? Two monomers react to form a larger unit while a small molecule is eliminated.
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condensation
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What are classic examples of condensation polymers?
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polyamides and polyesters
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what kind of polymerization is Nylon-10,6 produced?
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condensation polymerization
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Why do we use a diacid chloride in the making polymers condensation experiment rather than dicarboxylic acid that is typically used industrially?
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because the acid halide is more reactive.
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what is added to the polymerization rxn mixture to neutralize the HCl released each time a new amide bond is formed?
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NaOH
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What method of polymerization is used to make polystyrene?
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chain addition polymerization
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What does a chain addition polymerization involve?
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the use of an initiator that forms a reactive species
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What is the initiator in our polystyrene synthesis?
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Benzoyl peroxide
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What does benzoyl peroxide generate in chain addition polymerization of styrene?
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radicals
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What does the radicals generated by the benzoyl peroxide in chain addition polymerization do?
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they react with styrene monomer to begin the chain addition process.
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How does chain addition differ from condensation polymerization?
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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.
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What is the simplest vinyl-type monomer?
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ethylene
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In condensation polymerizations, what are the functional groups part of?
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polymer backbone and are formed as monomer units link together.
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How is the empirical formula in a condensation polymerization?
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the formulas of the monomer and polymer are different
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what is slime?
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cross-linked polymer
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how are the bonds in the cross-links b/w the borate ion and alcohol functional groups of PVA in slime?
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weak
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monomer
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repeating units that serve as the building blocks of a polymer.
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repeating unit
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group of atoms derived from a monomer and repeats throughout a polymer.
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condensation polymerization
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2 monomers react to form a larger unit while a small molecule, like H2O or HCl, is eliminated.
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cross-linked polymer
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polymer in which long-chain molecules are attached to each otherCan be covalent or ionic
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Why can't we use vinyl alcohol in polymerization?
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it almost exclusively exists in its tautomeric form, acetylaldehyde.
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How is the solubility of polystyrene in acetone? toluene? ethanol?
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semi-soluble-nothing -soluble
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Electrophilic aromatic substitution rxns are important way for what?
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to allow a functional group to be placed on an aromatic ring.
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What is an example of an EAS rxn?
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Friedel-Crafts acylation
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What has been referred to as a "superaromatic" molecule?
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Ferrocene
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What is a term that refers to techniques for separating, analyzing, and identifying compounds?
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chromatography
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What are the 4 types of chromatography?
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column-TLC -GC -HPLC
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what is the mobile phase?
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gas or liquid phase
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what is the stationary phase?
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a solid support that contains an adsorbent
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what are bands?
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areas of concentration
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If a component has a greater affinity for the stationary phase, it will
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travel more slowly.
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What are the basic steps of chromatography? -
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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.
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For column and thin layer chromatography, what is the adsorbent for the stationary phase?
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silica gel or alumina
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silica gel and alumina have what?
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many sites for H bonding
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in column and thin layer chromatography, what compounds tend to adsorb more readily to the stationary phase?
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polar
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In both column and thin layer chromatography, what is the solvent used for the mobile phase called?
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eluent
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True/False, an eluent can vary from very polar to less polar.
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True
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What is a developing chamber?
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a jar with a lid or a beaker with a watch glass cover
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on the TLC plate the sample components are separated on what phase?
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stationary
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what is the solvent front?
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leading edge of solvent
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What is the Rf value?
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a ratio from 0 to 1.
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equation for Rf?
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(distance from origin to center of the spot)/(distance from origin to solvent front)
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The Rf values for polar compounds are? for nonpolar compounds?
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smaller-closer to 1
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what interacts more strongly with the stationary phase?
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polar compounds
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Why is it important to keep the sample as concentrated as possible in column chromatography?
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so that the entire sample enters column in compact of a band as possible.
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How would Rf values change if a more polar solvent were used in TLC plate?
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would increase for all compounds
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Why is it important not to dilute the initial sample before it has been loaded onto the chromatography column?
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if you dilute the sample, it can become a wider band in the column, thus you would be unable to completely separate components
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Which compound would you expect to elute first from the column: unreacted ferrocene, acetylferrocene, or diacetylferrocene?
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Ferrocine (unreacted) because it is the least polar.
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what is the mobile phase used in our TLC experiment?
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methylene chloride
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What is the purpose of the cotton in the chromatography column?
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it will support the packing material and prevent it from clogging the stopcock during elution.
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Why should we never allow the volume of solvent in the column to go below the top of the adsorbent while packing the column?
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if the top of the adsorbent dries out, channels can form in the packing material that will cause poor separation.
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Yield calculation is only accurate if what?
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all of a sample is taken on to subsequent steps. always compare moles obtained of product in each step to moles of starting material.
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What extract is among the most widely used herbal remedies in the world?
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Ginkgo biloba
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What is an active component that is found in extracts of Ginkgo biloba?
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Ginkgolide B
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What did Corey develop the concept of?
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retrosynthetic analysis
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What are the steps in synthesising benzocaine?
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conversion of amine to amide-oxidation of benzylic carbon -hydrolysis of amido group -esterification of carboxylic acid
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what is benzocaine?
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local anesthetic
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what acts as a protecting group during the synthesis?
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amine to amide
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what do you use to decolorize in the protection step (1st) of multi?
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charcoal
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Why does the oxidation reaction mixture need to boil gently?
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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
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How can you induce crystallization?
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by scratching the walls of flask with glass stirring rod
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What functional group is seen in an IR spectrum peack at 1700?
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C=0
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what does a degree of unsaturation of 2 mean?
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two double bondsone double bond and one ring two rings one triple bond
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what is a more polar solvent we can use instead of ligroin when developing a TLC plate?
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ethyl acetate
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what is a very polar eluent that can be used besides ligroin in TLC?
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water or methanol
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in column chromatography, what compound elutes first?
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the least polar
