We report on the reactions of 2-iodo-1,1,1-trifluoroethane (CF3CH2I) on gallium-rich GaAs(100)-(4 x 1), studied using the techniques of temperature programmed desorption and x-ray photoelectron spectroscopy. The study is to provide evidence for the formation of a higher fluorinated alkene, 1,1,4,4,4-pentafluoro-1-butene (CF2 = CHCH2CF3) and alkane, 1,1,1,4,4,4-hexafluorobutane (CF3CH2CH2CF3) from the coupling reactions of covalently bonded surface alkyl (CF3CH2.) moieties. CF3CH2I adsorbs nondissociatively at 150 K. Thermal dissociation of this weakly chemisorbed state occurs below room temperature to form adsorbed CF3CH. and I-. species. The surface CF3CH. species undergoes beta-fluoride elimination to form gaseous CF2 = CH2 and this represents the major pathway for the removal of CF3H2. species from the surface. In competition with the beta-fluoride elimination process the adsorbed CF3CH2. species also undergoes, recombination with surface iodine atoms to form recombinative molecular CF3CH2I, olefin insertion reaction with CF2=CH2 to form gaseous CF2=CHCH2CF3, and last self-coupling reaction to form CF3CH2CH2CF3. The adsorbed surface iodine atoms, formed by the dissociation of the molecularly chemisorbed CF3CH2I, and fluorine atoms formed during the beta-fluoride elimination reaction, both form etch products (GaI, GaF, AsI, AsF, and As-2) by their reactions with the surface layer Ga atoms, subsurface As atoms, and GaAs substrate. In this article we discuss the mechanisms by which these products form from the adsorbed CF3CH2. and I-. species, and the role that the GaAs surface plays in the proposed reaction pathways. We compare the reactivity of the GaAs surface with transition metals in its ability to facilitate dehydrogenation and coupling reactions in adsorbed alkyl species. (C) 2004 American Vacuum Society.