Dehydration is a reversible process. Which of the two set-ups, distillation or
single flask, will generate the most cyclohexene? Why?

             Distillation will generate the most cyclohexene.

Explanation:

                     Let us assume following attached reaction for the synthesis of cyclohexene from cyclohexanol which attains equilibrium after certain time.

As shown in figure the cyclohexanol upon treatment with phosphoric acid undergoes dehydration reaction (removal of water) and produces cyclohexene. On the other hand cyclohexene reacts with water (hydration reaction) and produces cyclohexanol.

Now, if this reaction is allowed in a single flask it will attain equilibrium and will not generate the cyclohexene in high quantity. On the other hand if we apply Le Chatelier's principle ( removal of product moves the equilibrium in right direction) and distillate cyclohexene (boiling the cyclohexene to convert it into vapors and then collect it after condensation) will move the reaction in forward direction and will allow us to generate cyclohexene in high amounts.

vanderwaal's forces of attraction are the electrostatic intermolecular forces that exist in a molecule due to the temporary or permanent dipoles that are developed in a molecule. in , the major intermolecular forces are dipole-dipole interactions as the molecule is polar (bent structure). so the vanderwaal's forces of interaction in between molecules are the permanent dipole-dipole interactions that develop due to the dipole that exists in between the polar h - s bond. the positively charged hydrogen atom is attracted towards the negative end of the dipole that is sulfur of the adjacent molecule. therefore, these forces of attraction are relatively stronger than that of london dispersion forces that exist in non polar molecules.