Alkenes undergo the following reactions except

Alkenes are hydrocarbons that contain at least one carbon-carbon double bond in their structure. The double bond makes alkenes more reactive than alkanes (saturated hydrocarbons) and capable of undergoing several types of reactions, such as addition, hydration, and polymerization. However, alkenes do not undergo substitution reactions, which involve the replacement of one atom or group of atoms in a molecule with another atom or group of atoms. This is because the double bond in alkenes is too strong to break under normal conditions, which makes it difficult to substitute an atom or group of atoms in the molecule. Therefore, the correct answer to the question is substitution. Alkenes do not undergo substitution reactions.