Recent advances in the development of reliable methods for the chemical functionalization of the nanotubes provide an additional impetus towards extending the scope of their application spectrum. In particular, covalent modification schemes allow persistent alteration of the electronic properties of the tubes, as well as to chemically tailor their surface properties, whereby new functions can be implemented that cannot otherwise be acquired by pristine nanotubes. The electronic and structural properties of several groups (COOH, NH2, and CONH2) interacting with different SWNT will be calculated by using total energy ab initio calculations based on the density functional theory.