Dehydration of Cyclohexanol Lab Report Exp. #12 PDF

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This is the lab report for Chem 237, the organic chemistry lab, for experiment #12, The Dehydration of Cyclohexanol....

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Lindsay Vaughan Chem 237-558 TA: Cassidy Tibbetts 11/30/2021

Dehydration of Cyclohexanol Results and Discussion For this experiment, I aimed to understand how cyclohexanol can form cyclohexene by an elimination reaction through dehydration as well as understanding how reactions like this could be utilized to interconvert functional groups in an organic lab. The methods used to perform this lab successfully include conducting organic reactions, dehydrating cyclohexanol, and the purification of cyclohexene. To dehydrate the cyclohexanol, a 2:5 mixture of sulfuric acid and phosphoric acid is used. To begin experimentation, a simple distillation is set up in order to distill the cyclohexanol from its azeotropic mixture with water. Next, to the conical vial in the apparatus, I added 2.5g of cyclohexanol and boiling chips, while slowly adding in 1.2mL of dehydrating acid. I then secured all of the glassware on the apparatus with clamps and clamped it to the hood, with the heating mantle below it. Once secured, I added the thermocouple of the digital thermometer to the apparatus by inserting it at the top. I then heated the reaction to boiling and continued to distill the cyclohexene collecting. We aimed to keep the temperature above 70 degrees celsius, but below 90 degrees celsius. The mixture began to boil around 68.7 degrees celsius and unfortunately hit a high of 98 degrees celsius. By the time there was only a little of the mixture left (about 1.5mL), I had only collected 1.8mL of cyclohexanol. Because we had little product, the TA advised my lab partner and me to skip the second distillation and to work with the product we had. With this product, the aqueous layers were separated to leave only cyclohexene. This cyclohexene layer was then dried with calcium chloride. Once dried, the cyclohexanol was weighed in the vial. The dry conical vial was weighed out to be 24.526g and 25.065g with the cyclohexene. These measurements give an actual yield of 0.539g of cyclohexene. Given that we started with 2.5g of cyclohexanol, the theoretical yield would be 2.05g (found by dividing 2.5g by cyclohexanol molar mass and then multiplied by the molar mass of cyclohexene). With this information, the percent yield is calculated to be 26%. Next, both a bromine test and a permanganate test (Baeyer’s Test) were performed on the sample. For the bromine test, 3 drops of the alkene product were dissolved in 2mL of hexane. Then, the bromine reagent was added dropwise. When this was added, the bromine color disappeared very quickly, indicating a positive result and a reactive alkene. The permanganate test was then performed by dissolving 3 drops of the alkene product in 2mL of 95% ethanol. Then, like the bromine test, potassium permanganate was added dropwise. When the potassium permanganate was added, the purple color disappeared and a brown precipitate formed in the bottom of the test tube, indicating another positive result. This then concluded the in lab experiment and the waste was disposed of in correct bottles in the hood and all glassware was

washed and dried. We were then given an IR spectrum of the cyclohexene product to analyze. This IR spectrum showed cyclohexene as shown by the peaks. This IR spectrum had large aliphatic C-H peaks at 3022.19cm^-1, 2924.53cm^-1, 2858.83cm^-1, and 2837.22cm^-1. There is also a C double bond C stretch at 1652.74cm^-1, a CH2 bend at 1437.26cm^-1 and a CH bend at 717.92cm^-1. All of these peaks and stretches show that the IR spectrum is indeed cyclohexene. During this lab, cyclohexene was successfully produced with high purity as it passed both the potassium permanganate test and the bromine test as well as being successfully identified on the IR spectrum. Because of the high purity of the product, it is unlikely that any water or cyclohexanol remained in the final product. This would be unlikely because of the washing of the product combined with the dehydration of the product with sodium carbonate. To obtain a high yield of product, the experiment had to be controlled and watched very carefully. During my experimentation, the temperature rose above 90 degrees celsius, which would be an unexpected error that potentially caused a lower yield of product. Another unexpected source of error would be when separating the layers out, some cyclohexene was extracted with the aqueous layer. Despite all of these errors, a pure product of cyclohexene was still able to be produced and therefore the experiment was able to be completed successfully....