As you have seen, dehydration and hydration are relatively reversible processes as the change in Gibbs Energy (?G) is small. Consider the form of Gibbs Energy equation (?G = ?H â T?S) ??? and address the following:
1. Consider the nature of the bonds broken and formed (?- vs ?-) and intuit the sign of the change in enthalpy ?H as positive or negative. (Or look it up.) Is it endothermic or exothermic?
2. Consider the number of moles of reagent vs product and intuit the sign of the change in entropy ?S as positive or negative. (Or look it up.) How is the position of equilibrium affected by temperature and concentration of acid?
Thermodynamic properties:
Cyclohexanol Thermodynamic Properties:
Hydration of Cyclohexene Required Reading Padias: Distillation pp. 55 Klein: Sec 9.4 echanism 9.2 SkiWBuilder 9.3 Introduction This experiment will involve the conversion of cyclohexene to cyclohexAnol. The first step of the reaction will involve the formation of cyclohexyl hydrogen sulfate through the reaction of sulfuric acid with cyclohexene. The cyclohexyl hydrogen sulfate will then be hydrolyzed to form cyclohexanol. OH OSO3H O. A H2SO4 (conc.) Procedure Apparatus for Steam Distillation Thermometer Addition (Separtory) Funnel Water out Distillation Water Adaptor Water In Claisen Conderser Adaptor Receiving Flask Distillation Flask of 2 Page Carefully add 4.5 mL of 14.3 M sulfuric acid (0.064 mole) to a 100 mL Erlenmeyer flask and add 5.0 mL (4.1 g, 0.049 mole) of cyclohexene. Cover the flask with aluminum foil and slowly stir (stirring bar) for 10 minutes or until a clear homogeneous solution is formed. Pour the resulting solution into a 100 mL round bottom flask, rinse the Erlenmeyer flask with 50 m L of water and add to the 100 mL round bottom flask. Fit the round bottom flask with a distillation adaptor and condenser set for steam distillation (above). Heat the mixture to hydrolyze the intermediate and dis until 25-30 mL of distillate has been collected Saturate the distillate with 10 mL of saturated sodium chloride (NaC) solution and add the saturated distillate to a sepatatory funnel. Collect, in a small flask, the smaller (organic) top layer then dry with a small amount of anhydrous sodium sulfate and decant into a clean pre- weighed 25 mL flask. Reweigh the flask to determine the yield and obtain an infrared spectrum (IR) of the product. Note: Experiment Adapted from Ault, A. Techniques and Experiments for Organic Qbomistg University Science Books: Sausalito, CA. 1998. Page 2 of 2
