Dehydration of Cyclohaxanol

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Experiment #9 Youngju Jeon With Tenzin Yingsal &Maria Sedrak November 13 Cyclohexene from Dehydration of Cyclohexanol 08 Fall Introduction: Dehydration of an alcohol to give alkenes is important transformation and is an example of elimination reaction. Strong mineral acids such as sulfuric a phosphoric acid catalyze the reaction (Wade, L. G. ). Dehydration of an alcohol can follow either the E2 or E1 mechanism. However, in each case, acid is required as a catalyst, because OH- is a strong base, it is a poor leaving group. But HOH is a weaker base, and better leaving group. Adding a strong acid to the mixture allows protonation of the –OH group to give water as a leaving group. Once this protonation occurs, the mechanism that is followed depends on the nature of the R group (Williamson, Kenneth L.). In the presence of a strong acid, an alcohol can be dehydrated to form an alkene. The acid used in this experiment is 85% phosphoric acid and the alcohol is cyclohexanol. The phosphoric acid is a catalyst and as such increases the rate of reaction but does not affect the overall stoichiometry. Since we are adding heat to the reactant, it is an endothermic reaction. Figure 1 shows the reaction scheme of this experiment. Figure 1. Reaction scheme Table 1. Listing of reactant and products Compound | M. W (g/mol) | Amount (g) | Moles (mol) | B.P. (°C) | M.P. (°C) | Density (g/mL) | Cyclohexanol | 100.16 | 3.84 | 0.0383 | 161 | 23 | 0.96 | Phosphoric acid | 97.995 | 1.685 | 0.0172 | 158 | 42.35 | 1.685 | Cyclohexene | 82.143 | 1.340 | 0.0163 | 82.98 | -103.5 | 0.811 | Procedure: First, obtain 4mL of cyclohexanol in 25mL round bottomed flask and add 1.0 mL of 85% phosphoric acid with the two boiling chips. Mix the content thoroughly by swirling before connection

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