Graphene is exactly one layer of carbon atoms arranged in a honeycomb lattice. Its large scale synthesis can be achieved by oxidizing natural graphite. Introduced oxo-functional groups make graphene water soluble, however, over-oxidation of the C-framework must be prevented, because structural defects are permanent and therefore, electronic properties can not be recovered by the removal of functional groups. We recently developed a new method to prepare almost intact graphene oxide (ai-GO) that bears very few structural defects with a density of defects as low as 0.01%. Since the framework of ai-GO is intact, oxo-functional groups are located on both sides of the basal plane and the contribution of functional groups at edges of defects and flakes play a minor role. Therefore, ai-GO is the ideal material to investigate chemical transformations at the basal plane. We found that the C-framework of ai-GO is thermally stable up to 100 °C and found that the framework is stable against acids and even base under controlled reaction conditions, while functional groups are already transformed. Functional groups are hydroxyl-groups, epoxy-groups as well as organosulfate groups with the latter at a concentration of up to one organosulfate on 30 C-atoms. These organosulfate groups were used to introduce azide groups by a controlled substitution.