Using a Dehydration Reaction to Convert an Alcohol to an Alkene
Date Due:
Date Submitted:
Purpose: ​The purpose of this experiment is to synthesize cyclohexene from cyclohexanol
involving distillation and liquid/liquid separation. Also, a bromine test will be used to verify the
product along with an IR spectroscopy.
Chemical Structures/Reactions:
+
H​2​SO​4​
⇔
+
H​2​O
Calculations:
Limiting Reagent:
1 mol
Cyclohexanol: 0.962 g/mL x 10mL x 100.2g
x 11 mol
mol = 0.0960 mol of cyclohexene
1 mol
Theoretical yield cyclohexene : 0.962 x 10mL x 100.2g
Percent Yield:
2.9932g
7.88g
x
82.1g
1 mol
=​ 7.88 g cyclohexene
x 100= 37.98%
Results:
Substance
Cyclohexanol
Physical
Description
of
Substance
Mass of
Initial
Reagents
(g)
Mass of
Substance
Isolated
(g)
Colorless
Gel-Like
Liquid
9.62
N/A
Percent
Yield
(%)
N/A
Distillation
Temperature
Range for
Substance
Isolated
(°C)
N/A
Br​2 ​Test for
Substance
Isolated
N/A
Cyclohexene
Colorless
Liquid
0.00
2.9932
37.98
74-80
Solution
remained clear
and colorless
IR Spectra Table:
Compound
Type of Vibrational
Motion
Characteristic
Functional Group
Frequencies (cm​-1​)
Actual Peak
Location from Data
(cm​-1​)
Cyclohexanol
●
●
O-H Stretch
C-O Stretch
●
●
3500-3200
13200-1000
●
●
3325.30
1064.79
Cyclohexene
●
●
-C=C- Stretch
=C-H Stretch
●
●
1680-1640
3100-3000
●
●
1653.05
3022.94
Discussion Questions:
1. Our percent yield of cyclohexane was low at 37.98%. This can be explained by a
multitude of things. For example, when placing the cleaned cyclohexane into the vial
some was spilt out onto the countertop. Another reason could be that when we were
distilling the liquid, we didn’t take the reaction flask as far as it could have gone.
2.
3.
The range of the experimental boiling point for cyclohexene was 74°C to 80°C. The
accepted boiling point range for cyclohexene is 82.9°C to 83°C, indicating that our
sample is not completely pure. This error could have been caused by human error in
distilling the solution. In the lab manual, it instruct the lab group to remove the receiving
flask when the temperature reaches 80°C and attach a new one because the fraction
collected between 80°C and room temperature was not cyclohexene. The lab group did
have a small amount of liquid distilled between room temperature and 80°C so a small
part of the fraction collect was impure.
4. The main difference between cyclohexanol and cyclohexene was a peak of 3325.30 cm​-1
present in they cyclohexanol, but not in the cyclohexene. This peak is related to the
alcohol group found in cyclohexanol. Both the cyclohexanol and the cyclohexene had
mostly similar peaks. Overall, since the cyclohexene did not have a peak at 3325.30 cm​-1
this provides evidence that cyclohexene doesn’t contain any impurities.
5. When the solution was mixed with Br2 the solution remained clear and colorless which
proves that the bromine reacted with the alkene to form colorless dibromide. If the
solution contained any impurities then the solution would have turned a reddish-brown
color.
Conclusion:
In conclusion, we were successfully able to turn cyclohexanol into cyclohexene via a
dehydration reaction. We found that the limiting reagent was cyclohexanol because it has the
least amount of product in the reaction. By using a distillation setup we were able to completely
change the 10 mL of cyclohexanol to cyclohexene the main purpose of the reaction. We then
washed the substance with 5 mL of 10% sodium carbonate, 5 ml of water, and then finally 5 ml
of saturated NaCl. After this, we used calcium chloride to dry this solution. After a week of
drying, we perform another distillation to remove the crude cyclohexene from the water after the
drying process. We found that the boiling range was from 74°C to 80°C meaning our solution
was not completely pure. After cooling we placed a sample of our acquired liquid and found that
the OH peak had completely disappeared meaning we did successfully convert the alcohol to an
alkene.
Elexis Farrell x
Ashley Howes x
Amrita Kapat x