Cyclohexene (boiling point = 83 °C) can be prepared by the dehydration of cyclohexanol (boiling point = 161 °C) using concentrated phosphoric acid - AQA - A-Level Chemistry - Question 3 - 2018 - Paper 3

To indicate that cyclohexanol has been dehydrated, you can add bromine solution to the cyclohexene. The addition of bromine, which is brown in color, will lead to a decolorization of the solution, confirming that a double bond has formed.

Sodium carbonate solution was used to wash the distillate to neutralize any residual acids present in the reaction mixture, preventing them from affecting further reactions.

It is important to open the tap of the separating funnel periodically to release any build-up of pressure from gases that might be generated during the reaction.

Anhydrous calcium chloride is hygroscopic, which means it has a strong affinity for water vapor in the atmosphere, allowing it to effectively remove moisture from the organic layer.

The apparatus consists of a round-bottomed flask connected to a vacuum pump, a Buchner funnel with filter paper placed on top, and a side arm flask. The mixture containing the drying agent is poured into the Buchner funnel, where the vacuum draws the liquid through the filter paper, leaving the drying agent behind.

Cyclohexene has a shorter retention time than cyclohexanol due to its lower molecular weight and lack of polar functional groups. This allows it to elute faster through the stationary phase in chromatography.

In the infrared spectrum, cyclohexene will show no O-H stretching absorption peaks, which are characteristic of alcohols like cyclohexanol. Therefore, the absence of such peaks would confirm that the product does not contain cyclohexanol.