The thermal chemistry of 1-chloro-3-iodopropane (ClC3H6I) adsorbed on Pt(III)

HREELS and XPS indicate negligible dissociation of ClC3H6I during adsorptio n at 100 K. During TPD, no ClC3H6I desorbs for coverages below 0.4 ML. For higher, but not multilayer coverages, parent ClC3H6I desorption occurs in t wo peaks, 200 and 230 K. After even larger doses, unsaturable multilayer de sorption occurs at 170 K. HREELS indicates that most C-I bonds dissociate b y 205 K. The following reaction paths are proposed on the basis of TPD and HREELS results. When the C-I bond breaks, 3-chloropropyl fragments, C(a)H2C H2CH2Cl, are formed and these either lose HCl to form eta(3)- or eta(1)-all yl or lose a beta-hydrogen to form 3-chloro-di-sigma-propylene. Some eta(3) -allyl groups hydrogenate to either propylene, some of which desorbs at 240 K, or n-propyl, some of which hydrogenates to release propane at 250 K. Ot her eta(3)-allyl groups isomerize to eta(1)-allyl. At 250 K, 3-chloro-di-si gma-propylene eliminates chlorine as HCl and also releases H atoms that hyd rogenate neighboring C-3 fragments. The eta(1)-allyl fragment either hydrog enates and desorbs as propylene at 325 K or isomerizes to propylidyne. Prop yl and di-sigma-propylene moieties rearrange to form propylidyne or release propylene at 325 K. Interestingly, there is some benzene desorbing at 375 K. To account for it, a diene metallacycle is suggested. Atomic iodine deso rbs at 825 K. Comparisons of the thermal chemistry of ClC3H6I on Ag(111) an d Ni(100) are made as are comparisons of ClC3H6I with other C-3 adsorbates on Pt(111).