SC CHEM 333 - Dehydration of Cyclohexanol to Cyclohexene Post-lab (4 pages)

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Dehydration of Cyclohexanol to Cyclohexene Post-lab



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Experiment 8 Dehydration of Cyclohexanol to Cyclohexene Post lab By Cameron Kahn TA James Collie 12 November 2013 Observations 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 or 10 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 Mass Density Volume Density 0 962g mL Mass Density Volume 5 96g Actual yield of cyclohexene 0 811g Mass Density Volume Density 0 811g mL Theoretical yield of cyclohexene 4 89g 2 Page Volume 6 2mL Mass Density Volume 0 811g Volume 1mL Cyclohexanol 1 mcyclohexanol 1 mCyclohexene 100 16 g Cyclohexanol 82 15 g Cycloh exene 1 mCyclohexanonol 5 9644 g 4 89 g Cyclohexene 1 mCycloh exe ne Percent yield of cyclohexene 16 58 Actual yield of product 0 811 g Percent yield x 100 x 100 Theoretical yield of product 4 89 g 16 58 Theoretical boiling point 83 0oC Actual boiling point 82 0oC Percent difference in boiling points 1 21 Theoretical boiling point Actual boiling point Percent difference in boiling points Average of bothboiling points x100 Conclusion 83 82 x100 82 5 1 21 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 would hinder 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 Page IR Analysis Sp2 hybridized Carbon 3100cm 1 Sp3 hybridized Carbon 2900cm 1 C C double bond 1700cm 1 References 1 Handy G 2012 Chemistry 334l essential of organic chemistry laboratory Montgomery Alabama QDE Press 2 Synthesis of Cyclohexene The Dehydration of Cyclohexanol The University of Massachusetts Amherst n d Web 10 Nov 2013 4 Page


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