Not very reactive. The double bond is called a functional group and is more reactive than the C-C single bonded regions of a molecule. Heating alkenes in water with an acid catalyst generates alcohols. The H behaves like a proton and is involved in hydrogen bonding. Diols contain two -OH groups.
Oxidation of alcohols leads to carboxylic acids.
Their formation is acid catalysed. Again, this is a condensation reaction. Polymer Reactions Addition polymerization occurs through the coupling of monomer groups. This is the process for the formation of polyethylene, polyproylene, polystyrene, polyvinyl chloride, natural rubber from isoprene, etc. These reactions require either an acid or radical group to initiate and then to terminate the process.