Alcohol Dehydration – synthesis of cyclohexene .

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5-4: Alcohol Dehydration
For this assignment, the target compound that you should synthesize is cyclohexene. This is an elimination reaction. Assess the potential of the possible
leaving groups. Keep in mind the mechanism and how that controls the outcome of the process.
Synthesis Procedures
1. To start this activity, click this link for Alcohol Dehydration . The lab will load in a new tab. Click back to this tab to read further instructions
and complete the questions below. Use the available reagents in the Alcohol Halogenation section in the Stockroom tab and identify the
appropriate starting materials required to synthesize the target compound and add them to the round bottom flask. Select the appropriate solvent
and drag the flask to the Stir Plate on the lab bench.
2. The contents of the flask will be visible in Live Data. From the group of reagents found on the lab bench, select the correct reagent to synthesize
the target compound and add it to the flask on the stir plate.
3. Start the reaction by clicking on the dials on the front of the stir plate. You should be able to observe the reaction mixture stirring in the flask.
Monitor the progress of the reaction using TLC measurements as necessary until the product has formed and the starting materials have been
consumed (if you have not previously completed the activity Using Thin Layer Chromatography, please see the note at the bottom of that
assignment regarding TLC in Beyond Labz). You can advance the laboratory time using the clock on the wall. You can also save your TLC plates
by clicking Save on the TLC window.
4. When the reaction is complete, “work up” your reaction by doing a separatory funnel extraction. Drag and drop the separatory funnel on the flask
and then add the appropriate solvent to the funnel. Remember that the addition of any aqueous solvent also adds diethyl ether, although this is not
shown (see note at the bottom of the activity Performing a Separatory Funnel Extraction). Either the organic or the aqueous layer can be removed
by clicking and dragging it to the bench. Your target compound should be in one of these layers. The other layer can be discarded into the red bin.
5. The layer in the round bottom flask may contain multiple products. To separate them, you must carry out a distillation. Drag the flask back to the
stir plate. Drag and drop the distillation apparatus onto the flask and attach flowing N2. Start the distillation by clicking on the Stir button. The
temperature of the distillation flask can be monitored by hovering your mouse over the thermometer. As the temperature increases, products will
evaporate and then distill into the collection flask at the back of the apparatus according to their boiling points. Products that are not needed can be
discarded until the desired product is isolated.
material
cyclohexanol.
starting
->
water
List the starting materials, solvent, reagent, and products formed: solvent
Reagent -> H2Son is
nonexene.
B
->
Remember that subscripts (AB) and superscripts (A ) can be included as needed using the _ and ^ characters respectively.
How long did it take to finish the reaction? Enter “oo” if reaction does not reach completion.
455050 minutes.
hours
What is the TLC value (Rf) for the Starting Materials?
If none are present enter “0”
What is the TLC value (Rf) for the Products?
If none are present enter “0”
Draw a mechanism for this reaction.
Please attach a file containing your drawn reaction diagram.
Choose File
no file selected
FTIR and NMR Spectra
After completing a reaction and working up the products, it is still necessary to confirm that the correct product was formed. The most common tools
used for this analysis are Fourier Transform Infrared (FTIR) and Nuclear Magnetic Resonance (NMR) spectroscopy. In the virtual laboratory, 1H and
13
C NMR spectra are available. Details on interpreting FTIR and NMR spectra are found in your textbook. Your instructor may or may not ask you to
perform this section depending on how your class is structured.
6. To collect an FTIR spectrum of your product, click on the FTIR spectrometer located to the right of the lab bench and drag the salt plate icon to
the flask on the lab bench. A window containing the FTIR spectrum for your product should now open. Identify the relevant peaks in the FTIR
spectrum and record the position and associated functional group for each below. The FTIR spectrum can also be saved to the lab book for later
analysis.
When entering values for the FTIR please enter them in order from left to right on the spectrum to ensure they match the grading rubric.
Position (1)
cm-1
Functional Group 1
Position 2
cm-1
Functional Group 2
Position 3
cm-1
Functional Group 3
7. To collect a 1H NMR spectrum of your product, click on the NMR magnet and drag the NMR sample tube to the flask on the lab bench. A
window containing the NMR spectrum for your product should now open. You can zoom into various portions of the NMR spectrum by clicking
and dragging over the desired area. The Zoom Out button is used to zoom back out to view the full spectrum. Identify all of the peaks in the NMR
spectrum and record the chemical shift, the splitting, and the number of hydrogens for each peak below. The NMR spectrum can also be saved to
the lab book for later analysis. If necessary to confirm the structure of your product, you can measure the 13C NMR for the product and record the
chemical shifts for the peaks. Mass spectrometry is also available if needed.
When entering values for the NMR please enter them in order from left to right on the spectrum to ensure they match the grading rubric.
Peak (1) Chemical Shift
Specify the multiplicity as a singlet (s), doublet (d), triplet (t), quartet (q), or multiplet (m).
Peak (1)
q
s
m
d
t
Specify the number of hydrogens associated with this peak.
Peak (1)
Peak (2) Chemical Shift
Specify the multiplicity as a singlet (s), doublet (d), triplet (t), quartet (q), or multiplet (m).
Peak (2)
q
s
t
m
d
Specify the number of hydrogens associated with this peak.
Peak (2)
Peak (3) Chemical Shift
Specify the multiplicity as a singlet (s), doublet (d), triplet (t), quartet (q), or multiplet (m).
Peak (3)
s
m
t
q
d
Specify the number of hydrogens associated with this peak.
Peak (3)
8.
Do the FTIR and NMR spectra you measured and recorded above confirm that you synthesized the assigned target compound? Explain.
Alcohol dehydration data:
TLC Plate:
FTIR
1 H NMR
Dehydration of Alcohol formation
–
of
cyclohexene.
Reaction.
->
of
H3POn/H2SO4
of H20
H30
–
calcohol
Reaction mechanism.
– >
–
H
H
–
–
d
+
wer:
Inco
#
+
HOT
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Dhwani. Desai
Chemistry 212
Dr. Pogban. Toure
March 1, 2023
Synthesis of 2 – hexanol
I. Purpose of the experiment
This activity aims to learn the usage of thin layer chromatography (TLC) and the chemistry
behind the synthesis of alcohol. TLC is a simple and fast analytical technique. It tells us about
the extent of the reaction. Moreover, the hydration of alkenes is the most widely used method
for the large-scale production of alcohol. This activity also involves the interpretation of FTIR and NMR spectra.
II. References
NELSON, D. J., BRAMMER, C. & LI, R., 2009. Substituent effects in acid-catalyzed
hydration of alkenes, measured under consistent reaction conditions. Tetrahedron
letter, 50, 6454-6456.
NOWLAN, V. J. & TIDWELL, T. T. 1977. Structural effects on the acid-catalyzed hydration
of alkenes. Accounts of Chemical Research, 10, 252-258.
SPIELMANN, J., BUCH, F. & HARDER, S. 2008. Early main‐group metal catalysts for the
hydrogenation of alkenes with H2. Angewandte Chemie, 120, 9576-9580.
WU, S., LIU, J. & LI, Z.2017. Biocatalytic formal anti-Markovnikov hydroamination and
hydration of aryl alkenes. Angewandte Chemie, 7, 5225-5233
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SANTOS, KARINA. (2020, June 16). Thin Layer Chromatography Lab Report.
https://www.studocu.com/en-us/document/austin-community-college district/organicchemistry/thin-layer-chromatography-lab-report/8622950
III. Reaction and Reaction mechanisms:
IV. Procedure
First, Alkene Hydration-2, tab was pressed, and a new tab was opened automatically. All the
instructions were read carefully. A stirrer and water as solvent was taken in a round bottom
flask. Then the assembly was dragged on the lab bench for stirring. From the data entry tray,
1-hexene was added to the round bottom flask under constant stirring. Then from the group of
reagents, H2SO4 was added as a catalyst. Then the flask was attached to the N2 supply, and the
condenser and heat was supplied to the reaction assembly under constant stirring. The reaction
was started by pressing the dials on the stir plate. When the reaction started, it was monitored
carefully, using TLC till all the reactants get consumed and the product was formed completely.
All the observations and time were noted. When the reaction was completed, “workup” for the
reaction was performed using extracting funnel. The separating funnel was dragged and
dropped on the flask. An aqueous solvent was added to the flask along with an organic solvent
i.e., diethyl ether. One of the layers was saved for calculations and results and all other
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remaining solutions were discarded in a red bin. All the calculations were performed, and
conclusions were drawn.
V. Result, Observation and Calculations:
a.) This is a screenshot of the experiment right after the reaction was started.
b.) This is a screenshot of the reaction once the reaction is finished.
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FTIR:
FTIR Reading:
Position
Functional Group
Absorption (cm -1)
(1)
(-OH bond)
3417
(2)
(-CH stretch)
2918
(3)
(-CH bond)
1392
•
NMR spectrum to confirm the target compound: yes, the FTIR and NMR spectra
confirmed the synthesis of the targeted compound. The peaks NMR spectra we
recorded; it concedes with the peaks for 2-hexanol. On the FTIR spectrum, a strong OH bond was absorbed around 3417 cm-1. This is to be expected since 2-hexanol is a
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six-carbon alcohol. Also, a strong -CH stretch was absorbed around 2918 cm-1. For
the NMR spectrum, six peaks were absorbed.
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1H NMR Reading:
Peak
Chemical Shift
Multiplicity
# of Hydrogens
associated
(ppm)
1
5.13
Singlet
1
2
3.88
multiplet
1
3
1.61
multiplet
2
4
1.32
multiplet
2
5
1.18
doublet
3
6
0.88
multiplet
2
VI. Discussion
Thin-layer chromatography is a technique that can be used to find out the constituents present
in a reaction medium. There exists a competition between the mobile phase, silica gel, and
stationary phase present on the thin-layer chromatography plate. Silica gel tightly held the
component that is more polar while the other components will elute up the thin-layer
chromatography plate.
The progress of the reaction was monitored by visualization of the TLC plate and the final
product was confirmed by the Rf value. Rf value is the ratio of the distance traveled by the
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component to the distance traveled by the solvent from the baseline of the TLC plate. It was
calculated by following the formula.
𝑅𝑓 =
𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑐𝑜𝑣𝑒𝑟𝑒𝑑 𝑏𝑦 𝑐𝑜𝑚𝑝𝑜𝑛𝑒𝑛𝑡
𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑐𝑜𝑣𝑒𝑟𝑒𝑑 𝑏𝑦 𝑠𝑜𝑙𝑣𝑒𝑛𝑡
VII.Conclusion
Thin layer chromatography is a powerful analytical technique used to study the progress of
reactions by identifying different reactants. TLC works on the phenomenon of the likedissolve-like principle. In this activity, 1-hexene was transferred to 2-hexanol via acidcatalyzed hydration of alkenes. The completion of the reaction was confirmed by TLC and the
components were identified by calculating Rf values. Further, the formation of alcohol was
confirmed by FTIR and NMR spectra.
VIII. Questions:
1. List the starting material, solvent, reagent, and product formed?
•
Starting material: sulfuric acid & 1- hexene
•
Solvent: H20
•
Product: 2 – hexanol
2. How long did it take to Finish the reaction?
•
It takes about 1 hour to finish the reaction.
3. What is the TLC value (Rf) for the starting material?
•
5/7 = 0.83 cm.
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4. What is the TLC value (Rf) for the product?
•
3.1/7 = 0.44 cm.
5. Does the FTIR and NMR spectra you measured and recorded above confirm that you
synthesized the assigned target compound? Explain.
•
Yes, With the help of the NMR and FTIR spectra data, the formation of the product 2hexanol is confirmed. On the FTIR spectrum, a strong -OH bond was absorbed
around 3417 cm-1. This is to be expected since 2-hexanol is a six-carbon alcohol.
Also, a strong -CH stretch was absorbed around 2918 cm-1. For the NMR spectrum,
six peaks were absorbed.