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SC CHEM 333 - Dehydration of Cyclohexanol to Cyclohexene Post-lab

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Experiment 8Dehydration of Cyclohexanol to CyclohexenePost-labBy: Cameron KahnTA: James Collie12 November 2013Observations:Initially, the first observation was that the reagents were clear and colorless. Upon heating the solution, a strong smell was noted. The presumed odor was from the cyclohexanol which was a faint camphor odor. Before transferring the mixture to the separatory funnel, the solution was observed to have a yellow hue. After separating and washing the solution, the next point of observation was during the qualitative tests for alkenes. Four test tubes were set up, two test tubes being controls while the other two would contain the final product. In the controlled test tubes, 1mL of cyclohexanol was added to each followed by either 10 drops of KMnO4 solution or10 drops of bromine water solution. In the test tube with KMnO4 and cyclohexanol, the solution formed two layers, one was purple in color. The two layers formed because the KMnO4 did not react. The other control test tube with the bromine water solution and cyclohexanol formed two layers as well, one being yellow in color while the other was clear in color. Upon the addition of 1% KMnO4 solution to the product test tube, a brown precipitant formed. The precipitant was Maganese Oxide. Next, the addition of the bromine water solution to the product formed two layers; one layer was yellow in color while the second layer was clear in color.Results:The starting volume of the reagent cyclohexanol was measured to be 6.2mL. From the reagent table, the density was found to be 0.962g/mL for cyclohexanol. Using the density equals mass divided by volume equation, one was able to rearrange to find the mass of cyclohexanol which was calculated to be 5.96g. Next the mass of the product, cyclohexene was calculated using the same density equation, just rearranged to solve for mass. The volume of cyclohexene was measured to be 1.0mL and from the reagent table, the density was to be 0.811g/mL. From the density equation, the mass of cyclohexene was calculated to be 0.811g. The percent yield of the final product was calculated to be 16.58%. The boiling point measured was 82.0oC while the theoretical boiling point was 83oC. The percent difference in boiling points was calculated to be 1.21%.Initial mass of cyclohexanol: 5.96g Density=MassVolume Mass¿ Density∗Volume Density=0.962g/mL =5.96g Volume=6.2mLActual yield of cyclohexene: 0.811gTheoretical yield of cyclohexene: 4.89g2 | P a g eDensity=MassVolume Mass¿ Density∗Volume Density=0.811g/mL =0.811g Volume=1mL5.9644 gCyclohexanol∗1 mcyclohexanol100.16 g Cyclohexanol∗1 mCyclohexene1 mCyclohexanonol∗82.15 g Cyclohexene1 mCycloh exene=4.89 g CyclohexenePercent yield of cyclohexene: 16.58%Theoretical boiling point: 83.0oCActual boiling point: 82.0oCPercent difference in boiling points: 1.21%Conclusion:Acid catalyzed dehydration is very important. This process occurs when an alcohol, preferably a tertiary alcohol, undergoes an elimination reaction through which a molecule of water from adjacent carbon atoms is eliminated by means of a heating acid catalyst such as phosphoric acid or sulfuric acid (Synthesis of Cylcohexene The Dehydration of Cyclohexanol). The experiment yielded positive results that allowed for a successful acid catalyzed dehydration of cyclohexanol into cyclohexene. On the contrary, there were some sources of error while performing the experiment. During transfer from flask to separatory funnel to test tubes, product was lost along the way. Also the distillation was not finished to completion due to time constraints which wouldhinder more product from forming. With these errors, the final mass of the product was noted to be 0.811g and the percent yield of cyclohexene was calculated to be 16.58%. This percentage is low due to loss of product through transferring and biproducts. The final product had a boiling point of 82oC. This boiling point compared to the theoretical boiling point is only a 1.21% difference. The very small margin between boiling points shows the product having little to no impurities. However, since it was not exact, some impurities could have been from unclean test tubes or from the separatory funnel. The IR supports the lack of impurities in our product and shows peaks of Sp3 hybridized carbons, Sp2 hybridized carbons, and a C=C double bond which is essential for any alkene. The qualitative test proved positive for alkene in our product. Upon the addition of bromine to our product, the solution turned clear in color. Bromine is a brown liquid that will turn to a clear color if there is an alkene present in the sample (Handy). Upon the addition of KMnO4 solution to the product, a brown precipitant formed. This brown precipitant was identified to be Maganese Oxide. Under diluted conditions, KMnO4 can show the presence of an alkene in a solution by forming a brown Maganese Oxide precipitant after oxidizing with an alcohol during the reaction. Both tests yielded positive results when compared with what theoretically should happen. Therefore, the conclusion was made that the product did include the presence of an alkene and the product was identified to be cyclohexene. 3 | P a g ePercent yield=Actual yield of productTheoretical yield of productx 100 0.811 g4.89 gx 100 =16.58% Percent difference in boiling points=Theoretical boiling point −Actual boiling pointAverage of bothboiling pointsx100 =83−8282.5x100 =1.21%IR Analysis:References:1. Handy, G. (2012). Chemistry 334l essential of organic chemistry laboratory. Montgomery, Alabama: QDE Press2. "Synthesis of Cyclohexene The Dehydration of Cyclohexanol." The University of Massachusetts Amherst, n.d. Web. 10 Nov. 2013.4 | P a g eSp2 hybridized Carbon3100cm-1Sp3 hybridized Carbon2900cm-1C=C double


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