Background
Read pp. 619-622 (McMurry, 7th ed.) for a discussion of reagents and the mechanism of alcohol dehydration. You will work in partners in this experiment. One partner will carry out the reaction via the traditional method, using a mixture of phosphoric and sulfuric acids as a catalyst. The other partner will carry out the reaction using a cation exchange resin as the catalyst.
Procedure
Place 2.0 g of cyclohexanol in a 5-mL conical vial. First Partner: Add 0.25 mL of 85% H3PO4 and 2 drops of H2SO4 to the reaction mixture. Second Partner: Add 0.20 g of the ion exchange resin (Amberlyst 15) to the reaction mixture. Add a spin vane or boiling stone and a Hickman distillation head fitted with a water-cooled condenser. Using an aluminum block on your hotplate/stirrer, gradually heat the mixture until the product begins to distil. Regulate heating so that the distillation takes 30-45 minutes. As crude product distils from the reaction mixture, use a pipet to transfer distillate from the Hickman still head to a closed vial.
When the distillation is finished, rinse the inside of the still head with 1 mL of saturated NaCl solution and add this solution to the product mixture. Remove the lower aqueous layer, then carefully decant the organic layer into a dry test tube, and add ca. 0.2 g of anhydrous Na2SO4. While the product is drying, clean and dry the Hickman head and spin vane. (NOTE: It is EXTREMELY important for the Hickman still head to be dry for the second distillation step.) Reassemble the apparatus. Pipet the clear organic liquid into a dry 3 mL conical vial and add a boiling stone or spin vane. Distill the product, collecting the fraction that boils between 82 and 85 oC.
Analyze your product by obtaining IR and NMR spectra of it. Be sure to weigh your distilled product and calculate a percent yield. Compare the product obtained using the traditional acid catalyst to that from the ion exchange resin.
Questions