The electronic and structural properties of functionalized semiconducting and metallic single-walled carbon nano-tubes (SWNTs) were investigated using spin-polarized density functional theory. The selected systems were SWNT-NH2, SWNT-NH2-OH and SWNTNH2-OH-COOH. Our results confirmed that, in metallic and semiconducting nanotubes with odd number of functional groups, an additional acceptor level is observed near the Fermi level, while systems functionalized with two groups retain their pure characteristic. The theoretical predictions reveal that the radical transfers from the functional groups to carbon atoms at the ortho and para sites of the six-membered ring. The calculated partial density of states and atomic polarizations confirmed this site dependence
