The gas-phase derivatization procedure was employed for direct (i.e., without chemical activation of terminal carboxylic groups) amidization of oxidized single-walled carbon nanotubes (SWNTs) with simple aliphatic amines. The procedure includes treatment of SWNTs with amine vapors under reduced pressure and a temperature of 160-170 degreesC. Applicability of infrared (IR) spectroscopy and temperature-programmed desorption mass spectrometry (TPD-MS) for chemical characterization of the derivatized SWNTs was analyzed. It was concluded that IR spectra of oxidized SWNTs treated with amines under different conditions (described here and elsewhere) cannot correspond to amide derivatives on SWNT tips because of the very low concentration of the terminal groups relative to the whole sample mass, which implies a negligible contribution to the IR spectra. The bands detectable in the case of long-chain amines correspond to amine molecules physisorbed because of strong hydrophobic interactions of their hydrocarbon chains with SWNT walls. Energetically preferable adsorption sites are the channels inside SWNTs, according to MM+ molecular-mechanics modeling. TPD-MS provided additional information on the chemical state of the amines. Heating of the amine-treated SWNTs at >200 degreesC causes cleavage of alkenes from the amine residues: nonene and pentene form in the case of nonylamine and dipentylamine, respectively. For the short-chain amine (dipentylamine), only one chemical form was detected, whereas two forms (amide and physisorbed amine) can be distinguished for the SWNTs treated with nonylamine. The content of physisorbed nonylamine is about 1 order of magnitude higher than the amide content. According to the results of two-level ONIOM quantum-chemistry-molecular-mechanics calculations, the direct formation of amides on armchair SWNT tips is more energetically favorable than that on the zigzag tips, although the activation barriers are of approximately equal height.