cyclohexene
In this experiment, cyclohexanol is dehydrated by aqueous sulfuric acid to produce cyclohexene as the sole product [equation (1)], and no rearrangement is possible in this reaction.

Secondary alcohols (2O) are somewhat easier to dehydrate requiring slightly lower temperatures, where Tertiary (3O) alcohols will undergo dehydration at room temperature or only slightly above that. The dehydration of cyclohexanol follows the E1 mechanistic pathway.

phosphoric acid
In the presence of a strong acid, an alcohol can be dehydrated to form an alkene. The acid used in this experiment is 85% phosphoric acid and the alcohol is cyclohexanol. The phosphoric acid is a catalyst and as such increases the rate of reaction but does not affect the overall stoichiometry.

Dehydration of substituted alcohols produces a mixture of isomeric alkenes. For example, refluxing 2-methylcyclohexanol in the presence of phosphoric acid gives 1-methylcyclohexene as a major product, 3-methylcyclohexene as a minor product, while very little methylenecyclohexane is formed.

The most commonly used Dehydrating agent is Ethanol because of its reliability, cost-effectiveness and excellent dehydration properties.

In the dehydration of cyclohexanol experiment, the reaction undergoes through a carbocation intermediate (E1 mechanism). The alcohol is protonated and a water molecule is produced in the reaction.

Satisfactory performance for several alcoholysis reactions was achieved with calcium carbonate catalysts even though at higher temperatures, typically greater than 200°C.

This results in the formation of an alkene, 1,2-dimethylcyclohexene, the same product obtained from the acid-catalyzed dehydration of 2,2-dimethylcyclohexanol.

1,1-dimethyl-3-cyclohexanol.

The acid used in this experiment is 85% phosphoric acid and the alcohol is cyclohexanol. The phosphoric acid is a catalyst and as such increases the rate of reaction but does not affect the overall stoichiometry. It can be seen from the balanced reaction that 1 mole of alcohol produces 1 mole of alkene.

Into a clean 100-mL round-bottom flask (it does not have to be dry – why?) place 10 mL of cyclohexanol (density = 0.963 g/mL) and then add 5 mL of 9 M sulfuric acid (wear gloves when handling the acid). Mix the contents of the flask by swirling it carefully. Clamp the flask and place a heating mantle under it.

In the presence of a strong acid, an alcohol can be dehydrated to form an alkene. The acid used in this experiment is 85% phosphoric acid and the alcohol is cyclohexanol. The phosphoric acid is a catalyst and as such increases the rate of reaction but does not affect the overall stoichiometry.

One molecule of cyclohexanol should produce one molecule of cyclohexene. One mole (mol) of cyclohexanol should produce one mole of cyclohexene. If 2.05 g of cyclohexanol is used (use the actual amount used in your experiment) convert this to moles by dividing by the molecular weight of cyclohexanol (MW = 100.2 g/mol).