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Duc Chau Chem 237 TA: Alexander Holter Experiment 12: Dehydration of cyclohexanol Results and Discussions The objective for this lab was to form cyclohexene by dehydrating cyclohexanol in an elimination reaction. The compounds used to dehydrate cyclohexanol was dehydrating acid that contained a 2:5 mixture of sulfuric acid and phosphoric acid. A simple distillation apparatus was set up to start the experiment. Then 2.5 grams (2.6 mL, 0.025 mol) of cyclohexanol were added to a 5-mL conical reaction vial with a few boiling chips. 1.2 mL of dehydrating acid was carefully added to the vial of cyclohexanol. The dehydrating acid was added slowly to prevent two layers of the mixture. Finally, the experiment started. The temperature was kept below 90° for the entire experiment for the simple distillation. A 2.0 mL of the cyclohexene-water azeotrope was collected in the distillate head. The 2.0 mL was then transferred to a test tube where only the cyclohexene and water layers were removed. The cyclohexene layer was dried with calcium chloride. The conical reaction vial’s weight was found out to be 24.992 grams and 25.549 grams when the layer was decanted into the vial. From there, the crude yield of cyclohexene can be calculated, IR spectrum can also be found from the sample with the Bromine Test and the Permanganate Test to see the effect of alkenes. The actual yield of cyclohexene was calculated to be 0.557 grams. Using this information, crude yield or percent yield can be calculated from using theoretical yield of cyclohexene. Since 2.5 grams of cyclohexanol was used for this experiment. Moles of cyclohexanol can be found from getting 2.5 grams divided by cyclohexanol's molecular weight, which was calculated to be 0.025 moles. Theoretical yield can be calculated from multiplying moles of cyclohexanol with cyclohexene hexene molar mass, which calculated to be 2.05 grams. From here, percent yield can be found from divide actual yield by theoretical yield of cyclohexene; the result was 27%. The IR spectrum of the mixture was given on

Ecampus to analyze. The sample was confirmed to be cyclohexene because of big C-H stretch peaks at 3022.50 cm-1, 2924.21 cm-1, 2858.61 cm-1, and 2837.32 cm-1. Also, there was a C=C stretch at 1652.73 cm-1 and a =CH bend at 717.95 cm-1. Furthermore, the results of the two tests were also positive. The results permanganate test was confirmed positive because of its yellow-brown color, which indicated that the precipitate of manganese dioxide had formed. The Bromine test was also positive because hydrogen could not evolve due to the yellow color quickly disappears. One of the sources of errors that happened during this experiment was that whenever collecting 2.0 mL of cyclohexene-water, there were two layers that can be seen. This is most likely due to not mixing the mixture carefully beforehand and not adding the dehydrating acid carefully. The crude yield results were low, most likely due to the simple distillation boiled more than it was supposed to. Also, when extracting there was a lot of cyclohexene layer extracted. However, this lab is deemed successful as this lab's objective was to form cyclohexene by dehydrating cyclohexanol in an elimination reaction and the objective was accomplished. Furthermore, the IR spectrum also confirmed that the dehydration of cyclohexanol products was to be cyclohexene. Therefore, this lab is successful despite a few lab errors that happened.

Figure 1 Cyclohexanol IR spectrum reference

Figure 2 Cyclohexene IR spectrum reference

Figure 3 Dehydration of cyclohexanol product IR spectrum...