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Orgo 1 Lab Fall 2023 Final Exam Review Flashcards | StudBud
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Orgo 1 Lab Fall 2023 Final Exam Review
Orgo 1 Lab Fall 2023 Final Exam Review
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1
When you collect your crystals at the end of recrystallization lab, why do you wash with cold solvent?
Hot solvent would dissolve everything, both pure solid and impurities.
Cold solvent will dissolve all impurities.
Cold solvent will be much less likely to re-dissolve the solid.
Hot solvent can't go through the filter paper.
2
Which compound is the most polar? (Mobile phase is 3:1, hexanes : ethyl acetate)
D
B
C
A
3
Why is sulfuric acid a superior acid to HCl for effecting the acid-catalyzed hydration of alkenes?
Sulfuric Acid has 2 protons
Sulfuric acid is stronger than HCl
Sulfuric Acid is nucleophilic
Sulfuric acid is non-nucleophilic
4
A melting point for a known substance was high and broad. Why might that be?
The starting temp of the Meltemp was too high
The Ramp Rate of the Meltemp was too fast
The sample is impure
The sample is pure
5
What is the splitting pattern in the proton NMR of an isolated ethyl group (CH3CH2)?
Triplet,Quartlet
Quartlet, Triplet
Doublet, Triplet
Triplet, Doublet
6
If the compounds shown in the table were separated by column chromatography with ether, which would elute first?
Benzyl Acetate
p-nitrophenol
Benzyl Alcohol
1-napthalenemethanol
7
What is the relation between compounds A and C?
None of the above
Diastereomers
Constitutional isomers
Enantiomers
8
What is the electrophile in the above reaction?
the bromide in 1-bromobutane
1-bromobutane
the oxygen in sodium ethoxide
sodium ethoxide
9
Which of the following would be the best procedure for extracting acetaldehyde from an aqueous solution?
Two successive extractions with 50 mL portions of ether.
three successive extractions with 33.3 mL portions of ether.
three non-successive extractions with 33.3 mL portions of ether.
One extraction with a 100 mL portion of ether.
10
What was the purpose of using a reflux condenser?
prevents solvents from boiling off.
Made rxns go faster
prevent air contaminants
keep the rxn at a low pressure
11
What physical property will help you to determine the identity of your unknown solid in exp 1?
color
boiling point
melting point
dielectric constant
12
What is an azeotrope?
a mixture of 2 or more liquids that have similar boiling points
a mixture of 2 or more liquids that have the same polarity
a mixture of 2 or more liquids with a constant boiling point
a mixture of 2 or more liquids with a broad boiling point
13
Which of the following statements is(are) FALSE?
I and III
I and II
III
I
14
What is a forerun?
liquid that distills right before the boiling point of the liquid you want
a condition that results from distilling too quickly
the first fraction that distills
a liquid that distills long before the boiling point of the liquid you want
15
(BP Determine) A small stream of air bubbles exits from the cap. tube. As the bubble increase, what causes the bubbling
Atmospheric pressure has increased and water vapor is being produced.
The bubbles are the vapor of the unknown being forced out of the tube.
Air is escaping faster from the capillary tube due to an increase in temp.
Atmospheric pressure has decreased and water vapor is being produced.
16
When doing a column chromatography on an alcohol/ketone mix, which elutes first?
The ketone eluted first, because it is more polar than the alcohol.
The alcohol eluted first, because it is more polar than the ketone
The alcohol eluted first, because it is less polar than the ketone
The ketone eluted first, because it is less polar than the alcohol.
17
Why does the tube need to be sealed when obtaining MP of norborneol?
The product will boil off quickly after it melts
The product will sublime.
The water in the air will wet the product, lowering the MP.
The product will react with air, causing unknown impurities.
18
When doing TLC, you can write on the plate in pen and keep the developing chamber uncovered.
True
False
19
The product contains _____ stereocenters with a possibility of ____ stereoisomers forming.
4,2
2,4
4,4
2,6
20
What is the reaction mechanism for the above reaction?
SN2
E1
SN1
E2
21
1.000 g of the mix of compounds A + B. After extraction, the student isolates 0.200 g A and 0.201g B. What are the %s?
30% A and 70% B
50% A and 50% B
20% A and 20% B
40% A and 60 % B
22
Fractional distillation under atmospheric pressure would most likely be used to separate which of the following?
water (boiling point of 100 oC) and ethanol (boiling point of 80 oC)
ethyl acetate (boiling point of 77 oC) and ethanol (boiling point of 80 oC)
All of the Above
ethyl acetate (boiling point of 77 oC) and water (boiling point of 100 oC)
23
The chromatography that you performed separates the components of a mixture based on which physical property?
polarity/mass
nucleophile/electrophile
polarity/solubility
melting point
24
If the product was placed in a polarimeter, there would be no rotation due to the presence of a racemic mixture.
False
True
25
Which of the products is the most stable?
B
C
A
A and C are equally stable
26
How would the yield of norborneol product be affected if the alcohol was left under a vacuum for too long?
yield would be lowered due to low boiling point
yield would be lowered due to sublimation
the yield would not be affected
27
During the two-part exp. based on the rxn below, what are we distilling and which distils first?
diethyl ether and 1-ethoxybutane. 1-ethoxybutane distils 1st.
diethyl ether and 1-ethoxybutane. diethyl ether distils 1st.
ethanol and 1-ethoxybutane. ethanol distils 1st.
residual sodium ethoxide and 1-ethoxybutane. 1-ethoxybutane distils 1st
28
A solid dissolves in hot methanol. During hot gravity filtration, crystals form on the filter paper. What should you do?
Rinse the filter paper with cold water.
Rinse the filter paper with cold methanol
Rinse the filter paper with hot methanol.
Rinse the filter paper with hot water.
29
If you were to perform TLC on a mixture and none of the pigments moved from the baseline, what do you do?
Make the mobile phase more polar
Make the mobile phase less polar
30
If the crystals are orange, you are instructed to wash them with aqueous sodium thiosulfate. Where is filtrate disposed?
Halogenated waste
Non-halogenated waste
31
In the molecule shown below, which proton (Ha-Hd) will be the most downfield in the 1H NMR?
Ha and Hd
Hd
Hc
Hb
32
What would be the effect on the Rf values if TLC were run with hexane rather than ethyl acetate as the eluent?
No Effect
Increase
Decrease
33
When doing the spinach extraction, why do we add acetone when crushing the leaves?
to solubilize the water in the spinach leaves
to solubilize the organic plant pigments in the spinach leaves.
to solubilize the aqueous plant pigments in the spinach leaves
to solubilize the cellulose in the spinach leaves.
34
What type of reactive intermediate is formed in the reaction of an alkene with H
2
O and H
2
SO
4
to give an alcohol?
A Carbocation
A Carboanion
A Carboxylic Acid
There won't be any intermediate.
35
In fractional distillation, a large surface area for condensation is provided through
A column with glass beads
a reflux column, no glass beads
a large boiling flask
A large collection flask
36
If 0.67 g of pure solid is collected from 0.85 g of crude solid, what is the percent recovery?
127%
79%
22%
92%
37
When using Siwoloboff’s method, when is the thermometer read to determine the boiling point of the unknown liquid?
When the entire setup is cooled down and the water stops boiling.
When the entire setup is cooled down and air stops leaving the tube.
When the setup is still hot, the unknown begins to enter the capillary tube
When the setup cools down, the unknown begins to enter the capillary tube
38
Why do steam distillation over simple or fractional distillation?
The Compounds have the same polarity
The Compounds are both volatile
The Compounds are close in boiling point
The Compounds are at risk of decomposing
39
During the workup of the reaction, diethyl ether is washed with brine solution. What is the purpose of this wash?
It removes traces of water in the ether layer.
Solubilizes any excess NaBr/salt.
Creates more distinct separation in the Sep. Funnel
None of the above
40
How will the melting point change if the solid sample is impure?
Lower and narrower than expected
Higher and broader than expected
Lower and broader than expected
Higher and narrower than expected
41
If a proton is closer to an electronegative atom, the proton will shift more upfield.
True
False
42
What does it mean if a mixed solvent system such as ethanol/water is suggested for a recrystallization?
Dissolve in a mix of hot ethanol and water
First add to hot water, then add drops of hot or cold ethanol
First add to hot ethanol, then add drops of hot or cold water
First add to warm ethanol, then add drops of hot or cold water
43
The MP of diastereomers will be _____, the MP of enantiomers will be ______.
different, the same
different, different
the same, different
the same, the same
44
A precipitate is formed during the reaction. What is the precipitate and how is it removed from the reaction mixture?
NaBr, collected by vacuum filtration.
NaBr, quenching with aqueous layer during work-up
NaBr, collected by gravity filtration
NaBr, extracted into organic layer during work-up
45
Which of the factors below are not considered when interpreting a proton NMR spectrum?
Splitting
Integration
Chemical Shift
Retention time
46
If you have a dissolved colored impurity when you dissolve your unknown in the appropriate solvent, you should?
any of the above might work depending on the impurity.
Add activated charcoal after you do the gravity filt.
Add activated charcoal before you do the gravity filt.
do all the steps for recrystallization normally
47
How could you distinguish the two samples by IR spectroscopy?
3100-3000 cm-1 due to an alkene functional group
1700-1850 cm-1 due to an aldehyde group
3500-3200 due to an alcohol group
1430-1645 cm-1 due to an aromatic functional group
48
Diastereomers have the direct opposite R/S configurations.
False
True
49
Which conditions favor the addition rxn?
Decrease the amount of sulfuric acid
Reduce the amount of the alkene reactants.
Increase the amount of water.
Nothing can favor addition
50
When Performing an extraction with Hexanes and water, hexanes will be the top layer.
False
True
51
The following products are diastereomers
True
False
52
what is the dibrominated product the result of?
Anti-addition
Syn-addition
53
When doing an extraction with DCM and water, water will be on top.
True
False
54
A student got these amounts of her compound after three extractions: 0.45g, 0.23g, 0.30g. Why is this not possible?
shouldn't get smaller amounts of compound with each successive extraction.
should obtain smaller amounts of compound with each successive extraction.
There is no correlation of amounts obtained to number of extractions
55
When distilling your fermentation mix, 3 fractions were collected. Which fraction should have the highest ethanol %?
Fraction 3
They have equal amounts of ethanol.
Fraction 1
Fraction 2
56
Using your knowledge of reaction mechanisms, determine which of the following statements is
not
true?
SN rxns favor products when leaving group base is weaker than nucleophile
Good leaving groups are often weak bases with strong conjugate acids.
Good leaving groups are often strong bases with weak conjugate acids.
SN rxns favor products when leaving group base is stronger than nucleophile
57
How does a boiling stone or stir stick prevent superheating?
it evenly dispurses the heat in the solution
it provides a surface on which gas bubbles can form
it prevents to formation of too many gas bubbles
it provides a surface on which the solution can cool
58
RF Value= (distance traveled of dot)/(Distance of solvent front)
False
True
59
Which of the following solvents is
not
a polar protic solvent: CH3OH, CH3CN, CH3COOH, H2O?
H2O
CH3CN
CH3OH
CH3COOH
60
How could a water-insoluble, organic base be separated from a water-insoluble, neutral organic compound?
Dissolve both compounds in ether and extract it with an acid.
Dissolve both compounds in ether and extract it with a base.
Dissolve both compounds in ethanol and extract it with a acid.
Dissolve both compounds in acetone and extract it with a base.
61
Using the data below, what was the density of the first fraction? (Beaker=20.23g, B+fraction=24.74, volume of frac.=5mL)
2.804 g/mL
0.904 g/mL
4.54 g/mL
4.95 g/mL
62
Which of the following statement(s) is(are) TRUE?
I and II
I and III
All of the statements are true.
II and III
63
Which solvent pairs are NOT good for doing an extraction?
diethyl ether and water
none of the above
Water and acetone
methanol and water
64
What are the properties of a good recrystallization solvent?
dissolves the solid when hot
dissolves the solid when cold but not when hot or at room temp
dissolves the solid when hot but not when cold or at room temp
dissolves the solid no matter the temperature
