In this review article, we explore covalent chemical strategies for the functionalization of carbon-nanotube surfaces. In recent years, nanotubes have been treated as chemical reagents (be it inorganic or organic) in their own right. Indeed, from their inherent structure, one can view nanotubes as sterically bulky, pi-conjugated ligands, or conversely as electron-deficient alkenes. Hence, herein we seek to understand, from a structural perspective, the breadth and types of reactions single-walled nanotubes (SWNTs) can undergo in solution phase, not only at the ends and defect sites but also along the sidewalls. Controllable chemical functionalization suggests that the unique electronic and mechanical properties of SWNTs can be tailored in a determinable manner. Moreover, prevailing themes in nanotube functionalization have been involved with dissolution of tubes.