The surface chemistry of 1-iodopropane adsorbed on Pt(111)

On Pt(111) at 110 K, 1-iodopropane, C3H7I, adsorbs molecularly, but for doses below 1.7 x 10(14) molecules cm(-2), only H-2 and I appear in thermal desorption. C-I bond cleavage occurs between 160 and 220 K, forming adsorbed n-propyl, C(a)H2CH2CH3, and atomic iodine, based on temperature-programmed desorption (TPD), high-resolution electron energy loss spectroscopy (HREELS), and X-ray photoelectron spectroscopy (XPS). n-Propyl undergoes beta-hydride elimination forming propylene, with desorption peaks at 185 and 240 K. At 240 K, hydrogenation to propane also occurs. Some di-sigma bonded propylene, C(a)H2C(a)HCH3, remains at 240 K and it rearranges to propylidyne near 300 K. Atomic H, bond to Pt, recombines and desorbs at ca. 260 K. Further desorption of H-2 is limited by C-H bond breaking and occurs over a broad temperature range with local maxima at ca. 280, 320, and 420 K, typical of propylidyne fragments on Pt. Atomic iodine desorbs in a broad feature at 825 K.