  Experimental and theoretical results on chemical functionalization of
graphene are reviewed. Using hydrogenated graphene as a model system, general
principles of the chemical functionalization are formulated and discussed. It
is shown that, as a rule, 100% coverage of graphene by complex functional
groups (in contrast with hydrogen and fluorine) is unreachable. A possible
destruction of graphene nanoribbons by fluorine is considered. The
functionalization of infinite graphene and graphene nanoribbons by oxygen and
by hydrofluoric acid is simulated step by step.
