I.
II.
Experimental Observation
After the short pre-lab lecture we had set out to gather the needed materials for the
experiment
Revisiting the pre-lab journal we followed the necessary steps for the experiment that
we were doing
It was just a matter of waiting and observing the temperature and once it hit the 45°C
mark, the temperature rose at a constant speed
We recorded that the first drop happened at 67°C, and the final drop happened at
82°C. The final volume was 4mL.
The experiment was easy enough to follow.
All of the details were jotted down on a hand out.
Calculation and actual yield
Weight of the test tube: 17.11 g ; weight of the test tube with the product: 19.49 g;
weight of the product: 2.38 g
% yield = actual/theoretical yield X 100 %
= 2.38 g / 4.1 g X 100%
= 58.05%
Discussion and Conclusion
While we were able to follow the necessary procedures that were required of us by
this experiment, we cannot fully say that what we did was successful for we weren’t able to
check the IR Spectrum of the final product and without this it’s really hard to tell if the
experiment itself was successful.
III. Post-Lab Questions
1. Why do you suppose that the dehydration of cyclohexanol to cyclohexene has been
the traditional experiment to illustrate the acid-catalyzed dehydration of an alcohol to
an alkene?
The dehydration of cyclohexanol to cyclohexene has been the traditional
experiment to illustrate the acid-catalyzed dehydration because cyclohexanol is the
best starting material for it mainly for the following reasons: a.) because of its
structure, it forms only one alkene upon the dehydration. b.) the rate of dehydration
of cyclohexanol using 85% phosphoric acid is relatively fast c.) cyclohexene can be
easily purified by distillation
2. Suppose 2-methylcyclohexanol were subjected to the conditions of this experiment
instead of cyclohexanol
a. What alkenes would you expect to be formed?
The product that we would expect to be formed will be 1-methylcyclohexene and 3methylcyclohexene
b. In what relative amounts would you expect them to be formed?
90% of 1-methylcyclohexene is expected to be formed.
3. When 3,3-dimethyl-2-butanol is boiled with 85% H3PO4 according to the procedure,
an elimination reaction takes place. If a carbocation mechanism is involved and the
initial carbocation undergoes elimination before rearrangement, the product should
contain only 3,3-dimethyl-1-butene. If the initial carbocation should rearrange, two
other alkenes could be formed: 2,3-dimethyl-1-butene and 2,3-dimethyl-3-butene.
Show the mechanism that forms the three products. Predict the major and minor
products. Explain your choices.