Synthesis of Cyclohexene via Dehydration of Cyclohexanol Discussion Part 1

The target product of cyclohexene was obtained through a dehydration reaction of cyclohexanol using 80% phosphoric acid as a catalyst and resulted in a 47% yield.  A fractional distillation column was used to separate the cyclohexene product from the remaining phosphoric acid and impurities.  The cyclohexene was purified at a boiling point (64 °C), which is far lower than the documented boiling point of cyclohexanol starting material.  The presence of cyclohexene was confirmed from the characterization analyses preformed.

Cyclohexanol dehydrates to yield cyclohexene in a one to one ratio.  Cyclohexanol (1.99 g) was used as a starting material and therefore should have yielded cyclohexene (1.64 g).  The actual yield of cyclohexene was 0.77 g, which gives a percent yield of 47%.  The low yield is most likely due to low-boiling components of cyclohexene and water that leave some product behind in the flask and in the column.  Using a high-boiling component, such as toluene, to continue the distillation, would most likely have helped recover product.  However, by eliminating this step, it greatly reduced the time spent on the experiment.