The thermal chemistry of 1- and 2-propyl moieties on Pt(111) was studied by using temperature-programmed desorption (TPD) and reflection-absorption infrared spectroscopy (RAIRS). The propyl intermediates were prepared via thermal activation of the C-I bond of 1- and 2-iodopropane adsorbed precursors, respectively. It was determined that the subsequent thermal activation of those propyl groups results in a competition between reductive elimination to propane, beta-hydride elimination to propene, and complete decomposition to propylidyne (and eventually to hydrogen and surface carbon). It was found that while the 2-propyl intermediate favors propene production, 1-propyl also yields significant amounts of propane. The formation of propene via beta-hydride elimination was identified by isotopic labeling TPD experiments, and directly about 200 K by RAIRS. Coadsorption experiments with hydrogen and deuterium were used to characterize hydrogenation and H-D reactions. All possible propene and propane isotopomers are formed from both 1- or 2-iodopropane on the D/Pt(111) surface, indicating that exchange is likely to occur via a cyclic propyl-propene-propyl mechanism involving the formation of both 1- and 2-propyl intermediates. Relative rates for 1-versus 2-propyl conversion were estimated.