CHM2211L Final

25 July 2022
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question
Empirical Formula and Molecular Formula calculations
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know how to do these
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Can IR Spectroscopy be used to distinguish 2-pentanone from 2-hexanone?
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No, becasue IR gives us information about which functional groups are present and both have the same group.
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Hot Gravity Filtration
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~the purpose of hot gravity filtration is to separate the solid and the liquid phases. ~it removes any impurities that are soluble when hot
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Why do you use a stemless funnel?
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it will prevent recrystallization from happening in the stem
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What is ligroin? Polar or nonpolar?
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Ligroin is a volatile, flammable, hydrocarbon solvent that is nonpolar. It is used to examine solubility
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Miscible or nah? (immiscible) hexane and water? Methylene chloride and water ethanol and water ether and water
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(write whats on top) immiscible (hexane on top) Immiscible (water on top) miscible immiscible (ether on top)
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Why is phenol more acidic than cyclohexanol?
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The phenol anion is resonance stabilized. this makes it a weaker conjugate base and a stronger acid than cyclohexanol
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The pKa of 2,4-dinitrophenol is 3.96. Could you separate it from benzoic acid using the extraction procedures in this experiment?
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no, becasue the pKa's are too close. they would be deprotonated stuff at the same time.
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Describe the practical reasons behind the direction of flow of water through the condenser
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The condenser needs to be slightly angled downward so that the flow of water through the condenser can properly cool the vapors. The water must flow from bottom to top to allow the condenser to fill up and do so.
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Why is it important to soak the cloves in water for several minutes prior to beginning the distallation
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soak the cloves so they can become rehydrated making there be more accessible euganol in the soft tissues allowing a better yield.
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Why must glassware be free of water in a grignard?
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grignards are very reactive with water becasue they are very strong nucleophiles. if there is any water present, the grignard will attack that rather than what we actually want. PH-MgBr + H2O --> Ph + Mg(OH)Br
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know how to do IR and NMR
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okay
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What is the purpose of Salicylamide?
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has properties of an analgesic and antipyretic. It has medical uses similar to aspirin. pain relief.
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Major Iodination product.
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you pick the one with least steric hinderance. both have the iodine meta to the electron withdrawing group. one has the iodide para to the OH electron donating group while the other s the ortho. the para one allows for less steric hinderance
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Rf formula
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Rf= distance from origin to dot/ distance from origin to solvent front
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how to tell if something is most polar:
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most polar travels shortest distance and has an Rf furthest from 1.
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what would happen if a more polar solvent is used?
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each compound will travel faster and further giving it a higher Rf value.
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why is it important to not dilute the initial sample before it has been loaded onto the chromatography column?
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It is important to not dilute the initial sample so that the entire sample enters the column in as compact of a band as possible.
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which compound would you expect to elute first from the column: unreacted ferrocene, acetylferrocene, or diacetylferrocene?
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I would expect unreacted ferrocene to elute first because it is least polar
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resonance structures
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know how
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why is the isolation of p-amino benzoic acid so difficult in the multi step rxn?
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The isolation of p-aminobenzoic acid is difficult because of the isoelectric point. The isoelectric point is the pH where a molecule contains both charges or no net electrical charge. This makes our lab more difficult because benzocaine is the ethyl ester of p-aminobenzoinc acid which is neutral meaning it has no charge and s harder to remove because it forms a zwitterion. If the pH is lower than the isoelectric point, the molecule will have a positive charge and if the pH is higher the molecule will have a negative charge.
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Is chlorophyll b more or less polar than chlorophyll a
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b is more polar than a. this is because chlorophyll a has a methyl group where cholorphyll b has a carbonyl group. the carbonyl causes b to be more polar bc of the electronegativity.
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What is more polar? Xanthophylls or B-carotene
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Xanthophylls are more polar because it contains O and B-carotene only contians C and H groups.
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ethyl acetate polar or non polar solvent?
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polar because the oxygen from the carbonyl group is electronegative allowing a partial negative charge on the O and a partial positive on C.
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Why do we use pencil on TLC plates not pen?
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we use pencil because the ink from the pen will travel up the tlc plate with the solvent.
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monomer-
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repeating units that bind to other molecules to make up a polymer
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repeating unit
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part of a polymer made up of repeating monomers chemically linked together
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condensation polymerization
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two monomers react to form a larger unit while a small molecule like water is eliminated or lost
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cross linked polymer
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~slime~ polymer formed from polymers linking to each other
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we cant use vinyl alcohol to make PVA why?
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because it will tautomerize to acetaldehyde which it prefers so it will not polymerize
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How to tell if products from two synthetic routes are identical.
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mix the samples together and take the MP. if the range is large and lower its different.
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why use hcl rather than water
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HCl is used to dissolve p-phenotidin and not water bc HCl is a stronger acid and give a better yield
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what is the purpose of sodium acetate in the amide synthesis of acetophenetidin
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acts as a base to prevent it from becoming too acidic
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what is greener synthesis amide or ether?
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amide synthesis is greener because it doesnt require as much water. both require bad chemicals and extended heating
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what compounds are present in the extraction pdt?
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benzoic acid, 4-t- butyl phenol
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how can you figure what you actually had in extraction?
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testing the melting point
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equations for acid-base rxn in the extraction lab
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look at post lab
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difference between washing and extracting
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extracting is used to dissolve the material we want and leave the others behind washing dissolves impurities and leaves the others behind
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Why do ketones and aldehydes only add one eq and esters add 2?
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ester reform the the carbonyl because there are two oxygens on the same carbon. Ketones and aldehydes have just one O and the grignard can only attack once
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how do you remove the by product which is generated through a coupling reaction of phenylmagnesium bromide with bromobenzene in grignard experiment?
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Ligroin removed the byproduct of biphenyl. both are nonpolar, so the ligroin can dissolve the biphenyl. this caused the solution to go from pink to yellow.
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directing effects of the substituents on salicylamide
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iodine is para because it made it less sterically hindered
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mechanism of formation in EAS
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double bond grabs iodine cation
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does chromatography serve to purify samples
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yes. there were 2 distinct spots and in column chromatography there were 3 layers.
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which isomer of diacetylferrocene forms in EAS
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1,1'-diacetylferrocene would be formed because it is least sterically hindered. the carbonyl on the top ring is an ewg so it deactivates or prevents the second one from adding to the same ring.
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Why don't we simply oxidize p-toluidine with KMnO4 to make p-aminobenzoic acid?
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It is such a strong oxidizer so it would oxidize the p-toluidine further past p-aminobenzoic acid. it would make the no2 group into a nh2 group. this is why we use the protection step
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why dont we do the esterification step before the deprotection step in the mutlistep synthesis?
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if we did the esterification step prior to deprotection, then ethanol would attack and add to the C=O in the amide rather than forming the ester. this would make the rxn useless because the ester woudlnt be formed.
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Which solvent ratio gave the best separation of pigments in the spinach lab? Why? Can you improve the separation with a different ratio?
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~50:50 solvent ratio because there are equal amounts of polar and nonpolar solvents. this allows it to seperate polar and nonpolar pigments equally. ~ i would improve this by adding more polar solvent to increase Rf values
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Which is least polar? Most?
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chlorophyll b is most polar and b-carotene to be least polar. !!!!!!!!!!!!!!!!!!
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How could you improve the experiment (spinach)
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improve this by making sure each pigment is concentrated enough
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how to increase yield in eugenol lab
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-letting the cloves soak longer -slow down distillation process -make sure to remove all CH2Cl2 with the pipet
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distillation vs CO2 extraction
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~CO2 requires less time than distillation ~CO2 requires very high pressure and complex equipment ~distillation requires CH2Cl2 which is toxic but makes a purer pdt ~CO2 is nontoxic and readily available making it greener