Data And Report Submission - Dehydration Of An Alcohol (2pts) Dehydration of an Alcohol Are you completing this experiment online? Data Collection Yet Amount of reactant used in grams (9) Product obtained in grams (a) 1 1 172 (22pts) Calculations and Analysis (5pts) Amount of reactant In moles (5pts) Product obtained in moles C) Product theoretical yield Sta) Product percent yield (2015) write the equation for the action Role of the Acid Catalyst The dehydration of an alcohol requires a catalyst, usually an acid, for the reaction to occur. The acid plays two roles in the mechanism. First, the acid protonates the hydroxyl group, making a good leaving group of water. Then, the conjugate base of the acid removes a hydrogen cation from a carbon adjacent to the cation in the intermediate. Therefore, the acid is regenerated throughout the reaction as required to be a catalyst. The most common acid catalysts for the alcohol dehydration are sulfuric or phosphoric acid. Other acids, such as hydrochloric or hydrobromic acid, are not used because the small conjugate base ions could participate in a competing nucleophilic attack on the carbocation intermediate. Improving a Reversible Reaction Yield Alcohol dehydration is a reversible process, as the presence of water could recreate the alcohol from the alkene. To optimize the yield of the alkene, the reversibility can be addressed by distilling off the product as it is made. The removal of the alkene from the reaction mixture has two benefits. First, decreasing the alkene concentration pushes the equilibrium toward the product side. Second, the alkene is removed from the water in the reaction flask to reduce the reverse reaction. In the dehydration of cyclohexanol performed in this lab, distillation during the reaction works well as there is a large difference in the boiling points of the reactant (cyclohexanol bp-161 °C) and the product (cyclohexene bp=83 °C). Thus, the cyclohexanol remains in the reaction flask during the distillation to continue reacting with the acid. If any of the acid happens to distill over with the cyclohexene, it can easily be neutralized with aqueous sodium bicarbonate. Traces of water can also be removed by using a drying agent, such as anhydrous magnesium sulfate or calcium chloride.
