Ziyue Zhu
2015/2/20

 Introduction
The objective of this lab was to prepare cyclohexene by dehydrating cyclohexanol.
And then identified the cyclohexene by using ammonium cerium nitrate test, bromine test and refractive index.
The major reaction of this lab was:
(1)
This reaction is an elimination which means that during the reaction, H-X ( X can be halogen or OH) will break the bonds with the molecule and form double bonds
(pi-bonds).
(2)
In this specific reaction, the H-X small molecules can be determined to be H-OH. The reaction is also called dehydration reaction.
The presence of -OH group can be determined by ammonium cerium nitrate,
(NH
4
)
2
Ce(NO
3
)
6
. This compounds can react with alcohol and form red complex.
(NH
4
)
2
Ce(NO
3
)
6
(yellow) + R-OH (colorless) → [alcohol + reagent] (Red) (3)
The presence of a C=C (carbon-carbon double bond) can be determined by bromine.
Br
2 can react with carbon-carbon double bonds and form some colorless product which is different from the red-brown color of Br
2.
(4)
The first step of the experiment was to set up the distillation apparatus. Then, cyclohexanol, sulfuric acid and phosphoric acid was added into the flask and heated up the mixture with a sand bath so that the reaction(1) began. After collecting all the distillate in a container, the liquid was transferred into a centrifuge tube. The bottom layer in the centrifuge tube was removed by the Pasteur pipet and labeled as ‘ Acid’.
Anhydrous calcium chloride was added into the centrifuge tube in order to dry the water out of the top layer. After the top layer was totally dried, the top layer was moved into a small vial and weighed. The second part of this lab was qualitative tests.
Firstly, put few drops of the products into a spot plate. Run the Br
2 test in the first three spots with Pasteur pipets so that the reaction (4) happened. The changing of colors were recorded. Then, the ammonium cerium nitrate test was ran in the second three spots and the changing of colors were recorded. The reaction (3). At last, the refractive index of the product was measured and recorded.

 Data
Table 1: The results of Br
2 and (NH
4
)
2
Ce(NO
3
)
6 tests
(NH
4
)
2
Br
2
Ce(NO
3
)
6
Unknown
Orange
Faint Red
Cyclohexene
Orange
Not change
Cyclohexanol
Not change
Red
Table 2: The refractive index of the unknown product
RI at 22 o C RI at 20 o C Expected RI at
20 o C
1.4469
1.4478
1.4460
Table 3: The yield of the product
Actual yield
1.6457g
Expected yield
2.43g
Figure 1: The IR data of the cyclohexene
Error percentage
0.1245%
Yield percentage
67.69%

 Discussion and Results
The results of the Br
2 test was that the unknown product changed color which meant that the cyclohexene was truly formed. The results of the (NH
4
)
2
Ce(NO
3
)
6 was that the unknown product did turned a little bit red which means there was still some cyclohexanol remained in the product after distillation. The refractive index value of product was 1.4478 at 20 o C and the percentage of error was 0.1245%. This meant that although cyclohexanol was still in the products, the percentage was quite small. The reason why the (NH
4
)
2
Ce(NO
3
)
6 still turned red was that this test was so sensitive that even small contaminating amount of cyclohexanol could cause a slight color change.
This also explained why the result of the unknown product was faint red. The actual yield of cyclohexene was 1.6457g and the percentage yield was 67.69%.
The most possible reason for the error of yield was the product was weighed, a little of the product was used to run the qualitative tests. In addition, when pouring the top layer in the centrifuge tube, some of the liquid stayed with the Anhydrous calcium chloride in the centrifuge tube. For the error of the RI, the explanation was that the limitation of the instrument: in this lab, the simple distillation was used. Besides, differences between the boiling points of cyclohexene and cyclohexanol were not far enough to let them be separated completely.
 Post-Lab Questions ：
6. 1-methylcyclohexene
7. Faster. Because the carbon that -OH and -CH
3 attached to was a tertiary carbon which was the easiest to react.