Lab 9 - Synthesis of Cyclohexene
Intro: There are many methods for synthesizing alkenes. The general method used is elimination. In this lab, the synthesis of cylcohexene will be by the dehydration of cyclohexanol. This reaction is a 2-step E2 reaction Equations:
1.) Set up a simple distillation apparatus (Figure above, left) using a 50 ml round bottom flask for the distillation flask and keep the receiving flask (25ml) in an ice bath to prevent any loss of cyclohexene / water.
2.) To the flask add .10 mol of cyclohexanol and 3.0 ml of concentrated phosphoric acid along with a few boiling chips.
3.) Begin heating the flask and distill off approximately 6-8 ml of the co-distillate of the water and cyclohexene.
4.) Transfer the distillate to a separatory funnel (Figure above, middle) and wash the solution with a 10 ml portion of 10% sodium hydroxide solution to neutralize any remaining traces of acid.
5.) Transfer the organic layer to a small Erlenmeyer flask and add approximately 0.5 g of anhydrous sodium or magnesium sulfate to the flask.
6.) After letting the organic layer dry for several minutes gravity filter the solution into the smallest round bottom flask you have.
7.) Using a simple distillation apparatus distill your crude cyclohexene and collect the fraction that distills around approximately 80 degrees Celsius in a preweighed flask (36.02 g). Again collect your sample in an ice bath to prevent