Reflection adsorption infrared spectroscopy (RAIRS) and temperature programmed desorption (TPD) have been used to study the C-N coupling reaction on the Pt(111) surface. This reaction underlies the industrially important synthesis of HCN from NH₃ and CH₄ over platinum catalysts. The present study shows that the C-N coupling reaction is readily achieved in UHV in various ways, such as from coadsorbed CH₃, produced from thermal decomposition of CH₃I, and NH, produced from electron beam induced dissociation of adsorbed NH₃. The presence of surface CN is detected through its reaction with hydrogen to form a surface CNH₂ (aminocarbyne) species, which has characteristic RAIRS peaks, as well as by HCN desorption. The CN bond forms at ~ 500 K. From the fact that C-N bond formation occurs at a temperature above where all CH_x and NH_y species have dehydrogenated indicates that the reacting species are in fact surface C and N atoms. The reaction is strongly coverage dependant with respect to CH₃I. Results show that CN formation is not influenced by I_ads but rather by C_ads. The presence of surface CH and NH_y (y=1, 2) species have been confirmed by DFT calculations.