What is the condition for alkenes to react with halogens?

Alkenes react readily with halogens through an addition reaction known as halogenation. The key aspect of this reaction is that it can occur under standard conditions without the need for external energy inputs such as high temperatures, catalysts, or pressure.

The double bond present in alkenes is reactive, making them more susceptible to electrophilic attack by halogen molecules. When a halogen approaches the alkene, the pi bond of the alkene facilitates the interaction, leading to the breaking of the halogen bond and forming a halonium ion intermediate. This occurs spontaneously in many cases at room temperature and pressure, allowing the formation of dihalogenated products directly from the reactants.

This contrasts with the other choices, which suggest conditions that are not necessary for the reaction to occur. Their presence is not a requirement for the halogenation process to take place with alkenes.