Danil Bukhvalov Title: Four routes to chemical functionalization of graphene Abstract: The results of the DFT (density functional theory) modeling of chemical functionalization of different types of graphene are presented. For freely suspended graphene (both sides are available) the complete functionalization is the most favorable, which transforms, for the case of hydrogenation, graphene into graphane. The cases of another chemical species are also discussed. For the case of graphene on substrate (one-side functionalization) it turns out that the ripples play a crucial role as centers of chemical activity. It is shown that the chemisorbed impurities can stabilize the ripples. A nimimal model for the functionalization of epitaxial graphene is considered. The cases of functionalization by hydrogen and phenyl groups are discussed, with focus on clusterization of impurities and gap opening. The fourth type of graphene is a nanoribbon. Its chemical activity is shown to be much higher than for the bulk graphene.