The boiling point of a compound is influenced by its molecular structure and the types of intermolecular forces present. In the case of cyclohexanol and cyclohexene, we see a significant difference in their boiling points due to their different functional groups.
Cyclohexanol, being an alcohol, can form hydrogen bonds due to its hydroxyl (-OH) group. This ability allows cyclohexanol molecules to attract each other more strongly, leading to a higher boiling point. The boiling point of cyclohexanol is approximately 161 °C.
On the other hand, cyclohexene is an alkene that lacks the -OH group. As a result, it primarily experiences weaker van der Waals forces (also known as London dispersion forces). Without the strong hydrogen bonding that cyclohexanol experiences, cyclohexene has a significantly lower boiling point of around 83 °C.
In summary, the presence of hydrogen bonding in cyclohexanol contributes to its higher boiling point compared to cyclohexene, which relies on weaker intermolecular forces. Thus, during dehydration, the transformation from cyclohexanol to cyclohexene leads to a decrease in boiling point due to the loss of hydrogen bonding capabilities.