CHEM 51LB University of California Irvine Separation by Acid base extraction Lab Report

Analysis ReportSample Name
Sample ID
Data Filename
Method Filename
Batch Filename
Vial #
Injection Volume
Date Acquired
Date Processed
: 1-Butanol
:
:
: 51LB Elimination Lab – E1E2.gcm
:
:1
: 1 uL
Sample Type
: Unknown
Acquired by
Processed by
: System Administrator
: System Administrator
mV
TCD1
1.767
1.813
25
20
15
1.720
10
5
0
0.00
0.25
0.50
0.75
1.00
1.25
1.50
1.75
2.00
2.25
min
TCD1
Peak# Ret. Time
1
1.720
2
1.767
3
1.813
Total
Area
4299
47982
33748
86029
Height
3458
35818
23973
63249
Conc.
4.998
55.774
39.228
Area%
4.998
55.774
39.228
100.000
Analysis Report
Sample Name
Sample ID
Data Filename
Method Filename
Batch Filename
Vial #
Injection Volume
Date Acquired
Date Processed
: 2-Butanol
:
:
: 51LB Elimination Lab – E1E2.gcm
:
:1
: 1 uL
Sample Type
: Unknown
Acquired by
Processed by
: System Administrator
: System Administrator
mV
1.762
1.809
TCD1
40
30
1.718
20
10
0
0.25
0.50
0.75
1.00
1.25
1.50
1.75
2.00
2.25
min
TCD1
Peak# Ret. Time
1
1.718
2
1.762
3
1.809
Total
Area
11989
100764
62777
175530
Height
9122
72731
43473
125326
Conc.
6.830
57.406
35.764
Area%
6.830
57.406
35.764
100.000
Analysis Report
Sample Name
Sample ID
Data Filename
Method Filename
Batch Filename
Vial #
Injection Volume
Date Acquired
Date Processed
: 1-Bromobutane
: 51LB Elimination Lab – E1E2.gcm
:
:1
: 1 uL
Sample Type
: Unknown
Acquired by
Processed by
: System Administrator
: System Administrator
uV
TCD1
1.862
5000
4000
3000
2000
1000
0
0.25
0.50
0.75
1.00
1.25
1.50
1.75
2.00
2.25
min
TCD1
Peak# Ret. Time
1
2
3
1.862
Area
6451
Height
4635
Analysis Report
Sample Name
Sample ID
Data Filename
Method Filename
Batch Filename
Vial #
Injection Volume
Date Acquired
Date Processed
: 2-Bromobutane
: 51LB Elimination Lab – E1E2.gcm
:
:1
: 1 uL
Sample Type
: Unknown
Acquired by
Processed by
: System Administrator
: System Administrator
mV
TCD1
1.878
1.930
50
40
1.982
30
20
10
0
0.25
0.50
0.75
1.00
1.25
1.50
1.75
2.00
2.25
min
TCD1
Peak# Ret. Time
1
1.878
2
1.930
3
1.982
Total
Area
67967
84941
26309
179216
Height
49661
59953
18524
128138
Conc.
37.924
47.396
14.680
Unit
Mark
V
V
Name
Analysis Report
Sample Name
Sample ID
Data Filename
Method Filename
Batch Filename
Vial #
Injection Volume
Date Acquired
Date Processed
: 1-Butanol
:
:
: 51LB Elimination Lab – E1E2.gcm
:
:1
: 1 uL
:
Sample Type
: Unknown
Acquired by
Processed by
: System Administrator
: System Administrator
V
TCD1
1.887
1.935
0.020
0.015
1.837
0.010
0.005
0.000
0.25
0.50
0.75
1.00
1.25
1.50
1.75
2.00
2.25
min
TCD1
Peak# Ret. Time
1
1.837
2
1.887
3
1.935
Total
Area
4292
32681
25819
62792
Height
3277
24156
18711
46145
Conc.
6.835
52.047
41.119
Unit
Mark
V
V
Name
Analysis Report
Sample Name
Sample ID
Data Filename
Method Filename
Batch Filename
Vial #
Injection Volume
Date Acquired
Date Processed
: 2-Butanol
:
:
: 51LB Elimination Lab – E1E2.gcm
:
:1
: 1 uL
Sample Type
: Unknown
Acquired by
Processed by
: System Administrator
: System Administrator
V
1.888
1.939
TCD1
0.05
0.04
0.03
1.843
0.02
0.01
0.00
0.25
0.50
0.75
1.00
1.25
1.50
1.75
2.00
2.25
min
TCD1
Peak# Ret. Time
1
1.843
2
1.888
3
1.939
Total
Area
14594
126345
77815
218753
Height
11225
87802
53393
152420
Conc.
6.671
57.757
35.572
Unit
Mark
V
V
Name
Analysis Report
Sample Name
Sample ID
Data Filename
Method Filename
Batch Filename
Vial #
Injection Volume
Date Acquired
Date Processed
: 1-Bromobutane
: 51LB Elimination Lab – E1E2.gcm
:
:1
: 1 uL
Sample Type
: Unknown
Acquired by
Processed by
: System Administrator
: System Administrator
uV
TCD1
1.854
7500
5000
2500
0
0.25
0.50
0.75
1.00
1.25
1.50
1.75
2.00
2.25
min
TCD1
Peak# Ret. Time
1
2
3
1.854
Area
10329
Height
6933
Analysis Report
Sample Name
Sample ID
Data Filename
Method Filename
Batch Filename
Vial #
Injection Volume
Date Acquired
Date Processed
: 2-Bromobutane
: 51LB Elimination Lab – E1E2.gcm
:
:1
: 1 uL
Sample Type
: Unknown
Acquired by
Processed by
: System Administrator
: System Administrator
mV
1.885
1.937
TCD1
5.0
1.987
2.5
0.0
0.25
0.50
0.75
1.00
1.25
1.50
1.75
2.00
2.25
min
TCD1
Peak# Ret. Time
1
2
3
1.885
4
1.937
5
1.987
Area
7869
6815
2353
Height
5667
4797
1663
Chem 51LB Experiment 4
Report Scaffold
Dehydration of 1- and 2-Butanol and
Dehydrobromination of 1- and 2-Bromobutane:
Analysis of Gaseous Products by Gas
Chromatography
Instructions
Report scaffolds are provided to help you learn how to write about
the experiments you conduct. We began by providing general
questions for each section and examples of specific questions
connected to the current experiment. Now you will be responsible
for beginning to provide your own experiment-specific questions
and answering them for the introduction and theory sections.
General questions are still provided here for reference. For this
assignment, you will do the following in a separate, single
document that may not exceed a total of three pages (mechanism
drawings may be attached at the end of your document and do
not count toward the three page limit):
–Label each section of your document with the appropriate
heading (i.e. introduction, theory, results, etc.)
–Number your specific questions for the introduction and theory
sections with letters (i.e. A, B, C, etc.).
–For the results, discussion, and conclusion sections of this
assignment, answer the specific questions provided, using the
numbering given in this document.
–Use complete sentences in the third person passive voice, but
keep the general questions in mind when answering the specific
questions (including the ones you develop) for every section.
An example of the layout required is provided on Canvas.
Unless the rubric specifies otherwise, all responses should be
included in the body of your report submission and count toward
the page limit. This includes results tables. Check the rubric for
the assignment that tells you what to include. All other materials
(i.e. mechanisms, calculations, images) may go in the appendix
and do not count toward the page limit.
Post-Lab Report Format: MUST BE TYPED IN WORD OR A
SIMILAR PROGRAM, NOT AN ELN PAGE! Times New Roman;
12 pt. font; double spaced; 1” margins; no more than 3 pages; use
3rd person passive voice only (For example, “We dissolved the
white solid in 10 mL of hot water,” should be written as, “The white
solid was dissolved in 10 mL of hot water.”). Include your name,
student ID number, and lab course code. This format is NOT
OPTIONAL and TAs will return work as unsatisfactory if the
format is not followed.
Purpose/Introduction
General Questions:
What were we trying to accomplish with this experiment? How did
we plan to accomplish this? The purpose of an experiment is not
simply to introduce a student to a technique or reaction! What
reactants were employed? What techniques were used?
Theory
General Questions:
Assume you are writing for another student who has taken
organic chemistry before but might have forgotten some of the
details of reactions and lab techniques. What information about
the reaction and/or techniques being used in this experiment
would you need to remind them of to make sure they understand
what you did, why you did it, and what the results mean? Your
theory section should include:
–An overview of E1 and E2 reactions and their components.
–A brief overview of the factors and conditions that favor each
reaction.
–Which type of elimination will be favored in each reaction
–A hypothesis of the products that will be obtained for each
reaction, in order of relative abundance
Results
For your post-lab assignment, you will use and present the data
provided to you by the data quiz on Canvas. This data will be
different to that recorded from experiment videos and used for
your in-lab assignment.
You will need to discuss data from all four starting materials
obtained from the Canvas data quiz. Make sure to report the data
from all 8 reactions in your data set (2 trials for each elimination
reaction).
General Questions:
What important data were obtained in this experiment? The data
provided in this section should relate to the purpose(s) of the
experiment, but you do not need to point out the connections
here. Do not explain your results yet. Just provide them in an
organized format. Don’t forget to include any assigned unknown
number! You should include a table to organize your data.
Experiment-Specific Questions:
1. What were the percent compositions of the three possible
products for each of the four reactions? Make sure to report the
compositions for all 8 GCs provided to you.
Discussion and Error Analysis
General Questions:
How do the data obtained relate to the purpose(s) of the
experiment? How do you know the identity of the product and/or
unknown? Do the results make sense? What conclusions can
you draw from the data? What conclusions can you NOT draw
from the data? Does the data contradict itself at any point? (Note
that although you are provided with distinct, individual questions
here, sometimes the answers to these questions might overlap
with each other. That’s ok! In a lab report you would need to
decide how to tie these answers together.)
Experiment-Specific Questions:
2. What kind of elimination reaction did the 2-butanol reaction
undergo? How do you know? Are your findings consistent with
your hypothesis regarding the order of abundance of the
products? Draw a mechanism consistent with your findings
(attach to appendix). Can you draw the same conclusion from
both trials of the reaction?
3. What kind of elimination reaction did the 1-butanol reaction
undergo? How do you know? Are your findings consistent with
your hypothesis regarding the order of abundance of the
products? Draw a mechanism consistent with your findings
(attach to appendix). Can you draw the same conclusion from
both trials of the reaction?
4. What kind of elimination reaction did the 2-bromobutane
reaction undergo? How do you know? Are your findings
consistent with your hypothesis regarding the order of abundance
of the products? Draw a mechanism consistent with your findings
(attach to appendix). Can you draw the same conclusion from
both trials of the reaction?
5. What kind of elimination reaction did the 1-bromobutane
reaction undergo? How do you know? Are your findings
consistent with your hypothesis? Draw a mechanism consistent
with your findings (attach to appendix). Can you draw the same
conclusion from both trials of the reaction?
6. Do your GC data make sense? If not, what might explain this?
You might not be able to say with certainty but you can
hypothesize. If you determine that no errors occurred, analyze a
potential error. How would you test your hypothesis with an
analytical technique? What results from your test would support
your hypothesis? Why is it important to resolve this error?
Suggest a fix to the error and provide potential evidence to
support the claim that the error occurred and affected your
results.
7. What other errors were encountered during the experiment that
may have affected data collection? Avoid discussing mechanical
errors unless they were significant. As above, you might not be
able to say with certainty but you can hypothesize.
Suggest a fix to the error and provide potential evidence to
support the claim that the error occurred and affected your
results.
Conclusions and Future
Experiments
General Questions:
How would you summarize your results and analysis in 1-2
sentences? In other words, what is it that you want the reader to
remember after having read your paper?
What questions remain unanswered?
What questions were
raised by your results and analysis?
Experiment Specific Questions:
8. What were the major products from each of the four reactions
and what kind of elimination reaction did each reactant undergo?
9. Were the observed major products expected based on the
reaction conditions? Briefly summarize why. This should be 1-2
sentences.
10. If your data were inconclusive or questionable, how else might
you go about identifying the product(s) of the reactions or if the
data came out as expected, what is something you could do in a
future experiment to increase your knowledge about what
factor(s) may affect the results of the elimination reactions
covered in this experiment? (1-2 sentences maximum here!)
12/20/18
Report Scaffold: Experiment 4 (Elimination)
2/3/21, 11:29 PM
Report Scaffold: Experiment 4 (Elimination)
Submit Assignment
Due Tuesday by 11:59pm
Points 1
Submitting a file upload
File Types pdf
Complete your Acid-Base Separation post-lab assignment following the instructions included in
Elimination Experiment Report Scaffold – INSTRUCTIONS.
Save your assignment as .pdf.
Upload your post-lab assignment as a .pdf here.
You need to earn full marks in 17 of the 22 rubric items to achieve a satisfactory on this assignment.
Eliminations Spec Rubric
Criteria
Introduction
Ratings
Pts
1 pts
Full Marks
0 pts
No
Clearly states the overall goal of the experiment , including specific
Marks
1 pts
compounds and techniques used.
Theory 1
1 pts
Full Marks
0 pts
No
Clearly describes the components of the general elimination reaction and
Marks
what general type of product is formed. This should be done in no more than
3 sentences.
Theory 2
1 pts
https://canvas.eee.uci.edu/courses/32326/assignments/630351?module_item_id=1029132
1 pts
0 pts
Page 1 of 6
Report Scaffold: Experiment 4 (Elimination)
2/3/21, 11:29 PM
Full Marks
No
Clearly explains the differences between E1 and E2 elimination
Marks
1 pts
reactions.
Theory 3a –
1 pts
0 pts
Hypothesis
2-butanol
Full Marks
No
Marks
Theory 3b Hypothesis
1 pts
Full Marks
0 pts
No
Clearly provides a prediction of the relative abundance order of the products
Marks
1-butanol
Clearly provides a prediction of the relative abundance order of the products
produced from the elimination reaction of 2-butanol. Clearly explains which
type of elimination reaction will be favored.
produced from the elimination reaction of 1-butanol. Clearly explains which
type of elimination reaction will be favored.
Theory 3c –
1 pts
0 pts
Hypothesis
2bromobutane
Full Marks
No
Marks
Theory 3d Hypothesis
1bromobutane
1 pts
Full Marks
Results (ES
1 pts
0 pts
Q1) (BODY)
Full Marks
No
Marks
Clearly provides a prediction of the relative abundance order of the products
produced from the elimination reaction of 2-bromobutane. Clearly explains
which type of elimination reaction will be favored.
Clearly provides a prediction of the relative abundance order of the products
produced from the elimination reaction of 1-bromobutane. Clearly explains
which type of elimination reaction will be favored.
All of the following data from the gas chromatograms are presented in wellorganized table(s): the % composition for each of the 3 possible elimination
products for each of the four elimination reactions. Include results from both
trials for each reaction.
https://canvas.eee.uci.edu/courses/32326/assignments/630351?module_item_id=1029132
0 pts
No
Marks
1 pts
1 pts
1 pts
1 pts
1 pts
Page 2 of 6
Report Scaffold: Experiment 4 (Elimination)
Discussion 1
– Mechanism
(APPENDIX)
1 pts
Full Marks
Clearly draws out the mechanism that leads to the major product of the
elimination reaction of 2-butanol. All arrows must be drawn following
2/3/21, 11:29 PM
0 pts
No
Marks
1 pts
accepted electron-pushing rules. No more than two missing or incorrect
formal charges. All appropriate intermediates drawn. Appropriate acids and
bases used when necessary.
Discussion 2
– Mechanism
(APPENDIX)
1 pts
Full Marks
Clearly draws out the mechanism that leads to the major product of the
elimination reaction of 1-butanol. All arrows must be drawn following
accepted electron-pushing rules. No more than two missing or incorrect
0 pts
No
Marks
1 pts
formal charges. All appropriate intermediates drawn. Appropriate acids and
bases used when necessary.
Discussion 3
– Mechanism
(APPENDIX)
1 pts
Full Marks
Clearly draws out the mechanism that leads to the major product of the
elimination reaction of 2-bromobutane. All arrows must be drawn following
accepted electron-pushing rules. No more than two missing or incorrect
formal charges. All appropriate intermediates drawn. Appropriate acids and
0 pts
No
Marks
1 pts
bases used when necessary.
Discussion 4
1 pts
0 pts
– Mechanism
(APPENDIX)
Full Marks
No
Marks
Discussion 5
(ES Q2)
Clearly draws out the mechanism that leads to the major product of the
elimination reaction of 1-bromobutane. All arrows must be drawn following
accepted electron-pushing rules. No more than two missing or incorrect
formal charges. All appropriate intermediates drawn. Appropriate acids and
bases used when necessary.
1 pts
Full Marks
https://canvas.eee.uci.edu/courses/32326/assignments/630351?module_item_id=1029132
1 pts
0 pts
No
Page 3 of 6
Report Scaffold: Experiment 4 (Elimination)
1) Clearly and explicitly integrates data from results to support claims made
in discussion. 2) Clearly uses data to assess the validity of the original
2/3/21, 11:29 PM
Marks
1 pts
hypothesis regarding the relative abundance order of the products produced
in the elimination reaction or 2-butanol. Do data from both trials lead you to
the same conclusions? Why does the data support or refute the the original
hypothesis?
Discussion 6
1 pts
0 pts
(ES Q3)
Full Marks
No
Marks
1) Clearly and explicitly integrates data from results to support claims made
in discussion. 2) Clearly uses data to assess the validity of the original
1 pts
hypothesis regarding the relative abundance order of the products produced
in the elimination reaction or 1-butanol. Do data from both trials lead you to
the same conclusions? Why does the data support or refute the the original
hypothesis?
Discussion 7
1 pts
0 pts
(ES Q4)
Full Marks
No
Marks
1) Clearly and explicitly integrates data from results to support claims made
in discussion. 2) Clearly uses data to assess the validity of the original
1 pts
hypothesis regarding the relative abundance order of the products produced
in the elimination reaction or 2-bromobutane. Do data from both trials lead
you to the same conclusions? Why does the data support or refute the the
original hypothesis?
Discussion 8
1 pts
0 pts
(ES Q5)
Full Marks
No
1) Clearly and explicitly integrates data from results to support claims made
Marks
in discussion. 2) Clearly uses data to assess the validity of the original
hypothesis regarding the relative abundance order of the products produced
1 pts
in the elimination reaction or 1-bromobutane. Do data from both trials lead
you to the same conclusions? Why does the data support or refute the the
original hypothesis?
Discussion
1 pts
0 pts
9a – Error
Full Marks
No
https://canvas.eee.uci.edu/courses/32326/assignments/630351?module_item_id=1029132
Page 4 of 6
Report Scaffold: Experiment 4 (Elimination)
2/3/21, 11:29 PM
Analysis (ES
1) Clearly identifies probable error(s) that did occur or could have occurred
Q6)
that affect the GC analysis. 2) Clearly explains (in 1-2 sentences) why
resolving the error is relevant to the experiment.
Discussion
9b – Error
1 pts
Full Marks
0 pts
No
1) Clearly hypothesizes how the error occurred. Human and equipment error
Marks
Analysis (ES
Q6)
Marks
are not acceptable. 2) Clearly proposes a method or use of an analytical
1 pts
1 pts
technique that would allow you to support or refute the error hypothesis.
Discussion
1 pts
0 pts
10a – Error
Analysis (ES
Full Marks
No
Marks
Q7)
1) Clearly identifies probable error(s) that did occur or could have occurred
that affect data collection during the experiment. 2) Clearly explains (in 1-2
1 pts
sentences) why resolving the error is relevant to the experiment.
Discussion
1 pts
0 pts
10b – Error
Analysis (ES
Full Marks
No
Marks
Q7)
1) Clearly hypothesizes how the error occurred. Human and equipment error
are not acceptable. 2) Clearly proposes a method or use of an analytical
1 pts
technique that would allow you to support or refute the error hypothesis.
Conclusion
1 pts
0 pts
Full Marks
No
1) Clearly summarizes the results in the context of the objective(s). 2)
Marks
Clearly states whether the objective(s) was/were met or not, and includes 12 sentences that support that statement. 3) Clearly proposes at least one
1 pts
future experiment that builds upon the results of the experiment, with 1-2
sentences of justification based on chemical principles.
ExperimentSpecific
Questions
Written by
Student
1 pts
Full Marks
0 pts
No
Clearly includes reasonable and relevant questions, where no more than two
Marks
are not specific or not relevant to the experiment.
https://canvas.eee.uci.edu/courses/32326/assignments/630351?module_item_id=1029132
1 pts
Page 5 of 6
Report Scaffold: Experiment 4 (Elimination)
2/3/21, 11:29 PM
Total Points: 22
https://canvas.eee.uci.edu/courses/32326/assignments/630351?module_item_id=1029132
Page 6 of 6
Elimination Lab
Dehydration of 1- and 2Butanol and
Dehydrobromination of 1- and
2-Bromobutane:
Analysis of Gaseous Products
by Gas Chromatography1
REACTIONS: Elimination
TECHNIQUES: Gas Chromatography
In this experiment, we will compare and contrast eliminations
under acidic and basic conditions. We will conduct the acidcatalyzed dehydration of a primary and a secondary alcohol. We
will also conduct the base-induced dehydrobromination of the
isomeric halides. The stereo- and regiochemistry of the four
reactions will be investigated using gas chromatography to
analyze the product mixtures.
IMPORTANT SAFETY
INFORMATION
•
•
All alkyl halides, including 1-bromobutane and 2-bromobutane
are harmful if inhaled, ingested, or absorbed through the skin.
Wear gloves, and keep all chemicals/reactions in the hood at all
times.
Potassium tert-butoxide is corrosive and moisture-sensitive.
Avoid contact with skin, eyes, and clothing.
•
•
Sulfuric acid is corrosive and causes burns. Avoid contact with
skin and eyes. Notify the instructor if any acid is spilled.
1-butanol and 2-butanol are flammable and toxic. Avoid contact
with skin, eyes and clothing.
EXPERIMENTAL PROCEDURE:
*NOTE: in the experiment video, only two reactions are performed:
the dehydration of 2-butanol, and the dehydrobromination of 1bromobutane. Prepare the experimental portion of your notebook
for only those two reactions, see guidelines above and on ELN for
more detail.
PART A
A1. Dehydration of 2-Butanol
Obtain an experiment kit from the stockroom.
In a reaction tube, place 2 drops of concentrated sulfuric acid.
Add a boiling stone and connect the reaction tube to the gas
collection assembly as shown in Fig. 4.1.
Assemble the gas collection apparatus shown in figure 4.1 before
the reactants are mixed. To position the gas collection tube, carry
out the following steps:
•
•
Fit the collection tube with a septum stopper in one end.
Fill the collection tube with water. What is the purpose
of the water?
•
•
•
•
•
Insert the end of the Teflon tubing that is coming out
from the top of the septa into the collection tube all the way
up to reach the stopper.
Place your index finger over the open end of the tube
and invert it (water should have remained in the tube).
Place the tube, with the open end down, into a 250-mL
beaker approximately half full with water.
Remove your finger (the column of water should remain
in the tube.)
Connect the other end of the Teflon tubing to the
reaction tube as shown in figure 4.1.
After the assembly is complete, use a syringe to add 0.2 mL of 2butanol to the reaction tube and heat the mixture in a preheated
heating block. Don’t assume things aren’t hot. Hover your hand
near the object in question to feel for heat radiating from it just like
you would a pan on the stove if you weren’t sure whether it was
hot or not. Generation of gaseous product can be observed by
watching the rapid decrease of the water level in the collection
tube. Keep heating until no more bubbles escape from the
bottom of the collection tube. Remove the Teflon tubing from the
gas collection tube, and then from the beaker, before removing
the reaction tube from the heat, all the while ensuring your
collection tube stays below the beaker’s water level. Why is it
important that the collection tube stays below the water level?
Use this sequence of steps in shutting down the reaction to
prevent water from being sucked back into the hot reaction tube
while it is cooling down.
Label the beaker containing the
collection tube kept in the water and submit it to your TA for the
gas chromatographic analysis. Cool heating blocks between
reactions. Don’t place a reaction set up on a hot block as it may
cause a fire.
The butenes have been determined to elute from the nonpolar column (SE30) the GC is equipped with in the following
order: 1-butene, trans-2-butene, and cis-2-butene. If you did
not know the order of elution for the gases, how could you
determine it experimentally? Determine the relative amount (%
composition) of the three components of gas products, assuming
that the amount of each substance in the gaseous mixture is
proportional to the area under its corresponding GC peak. The
report provided from the GC instrument should provide relative
integration values for each peak. If the values are missing, you
can estimate the integration values by assuming that these areas
are equal to the peak height (mm) x the peak widths at a halfheight (mm).
A2. Dehydration of 1-Butanol
Repeat the procedure for part A1 using 1-butanol instead of 2butanol. Be sure to read chemical labels carefully and keep track
of which alcohol you are adding! Turn the hot plate off when
finished and let it and heating block cool to room temperature (at
least 15 minutes) before putting them away.
PART B
B1. Dehydrobromination of 1-Bromobutane
Obtain an experimental kit from the stockroom.
Assemble the gas collection apparatus shown in figure 4 before
the reactants are mixed. To position the gas collection tube, carry
out the following steps:
•
•
•
•
•
Fit the collection tube with a septum stopper in one end.
Fill the collection tube with water. What is the purpose
of the water?
Insert the end of the Teflon tubing that is coming out
from the top of the septa into the collection tube all the way
up to reach the stopper.
Place your index finger over the open end of the tube
and invert it (water should have remained in the tube).
Place the tube, with the open end down, into a 250-mL
beaker approximately half full with water.
•
•
Remove your finger (the column of water should remain
in the tube.)
Connect the other end of the Teflon tubing to the
reaction flask as shown in figure 4.
In a 10 mL round-bottom flask equipped with a water-cooling
condenser place 5 mL of 1M potassium t-butoxide (or 575 mg of
potassium t-butoxide powder and 5 mL of t-butanol) using a
pipette. Do not expose the potassium t-butoxide to air for too long
as this may produce some unexpected results when analyzing the
composition of products from the reaction. Why would exposing
potassium t-butoxide to air cause problems? Add a boiling stone
to the flask, and connect the condenser to the gas collection
assembly as shown in Fig. 4.
Assemble the gas collection apparatus shown in Fig. 4 before the
reactants are mixed. After the assembly is complete, use a
syringe to add 0.5 mL of 1-bromobutane to the reaction flask and
heat the mixture in a preheated heating block. Don’t assume
things aren’t hot. Hover your hand near the object in question to
feel for heat radiating from it just like you would a pan on the
stove if you weren’t sure whether it was hot or not Generation of
gaseous product can be observed by watching the rapid decrease
of the water level in the collection tube. Keep heating until no
more bubbles escape from the bottom of the collection tube.
Remove the Teflon tubing from the gas collection tube, and then
from the beaker, before removing the reaction tube from the heat,
all the while ensuring your collection tube stays below the
beaker’s water level. Use this sequence of steps in shutting
down the reaction to prevent water from being sucked back into
the hot reaction tube while it is cooling down. Label the beaker
containing the collection tube kept in the water and submit it for
the gas chromatographic analysis. Cool heating blocks between
reactions. Don’t place a reaction set up on a hot block as it may
cause a fire.
B2. Dehydrobromination of 2-Bromobutane
Repeat the procedure for part B1 using 2-bromobutane instead of
1-bromobutane. Be sure to read chemical labels carefully and
keep track of which alkyl halide you are adding! Turn the hot plate
off when finished and let it and the heating block cool to room
temperature (at least 15 minutes) before putting them away.
The butenes have been determined to elute from the nonpolar column (SE30) the GC is equipped with in the following
order: 1-butene, trans-2-butene, and cis-2-butene. If you did
not know the order of elution for the gases, how could you
determine it experimentally? Determine the relative amount (%
composition) of the three components of gas products, assuming
that the amount of each substance in the gaseous mixture is
proportional to the area under its corresponding GC peak. The
report provided from the GC instrument should provide relative
integration values for each peak. If the values are missing, you
can estimate the integration values by assuming that these areas
are equal to the peak height (mm) x the peak widths at a halfheight (mm).
For your in-lab assignment, you will record and use data provided
in the experiment videos. This means you will have data for the
dehydration of 2-butanol and the dehydrobromination of 1bromobutane. Make sure you adjust any sections in your notebook
accordingly to match compounds used in experiment videos,
including general reaction, mechanism, GHS tables, and
calculations. Think of experiment videos as your time in lab. For
this experiment, it is not necessary to record gas chromatography
data in your in-lab.
POST-LAB REPORT (3 page limit)
Complete the Experiment 4 Report Scaffold worksheet provided
on the class website and turn in to your TA at the specified time.
Be sure to read and follow the instructions provided on the
worksheet! Also check the template on Canvas so you know how
the scaffold is intended to be formatted. Attach all GC print-outs to
the end of your report (in the appendix).
For your post-lab assignment, you will use and present the data
provided to you by the data quiz on Canvas. This data will be
different to that recorded from experiment videos and used for
your in-lab assignment.
You will need to discuss data from all four starting materials
obtained from the Canvas data quiz.