The adsorption and thermal reactions of 2-iodoethanol on clean Ni(100) single-crystal surfaces were studied by temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). 2-Iodoethanol was chosen as a precursor for the preparation of 2-hydroxyethyl and oxametallacycle surface species, potential intermediates in hydrocarbon catalytic oxidations. It was found that 2-iodoethanol adsorbs molecularly at 100 K, in two configurations involving either just the iodine atom or both iodine and hydroxyl ends of the molecule. A complex chemical behavior starts around 140 K with the production of small amounts of ethylene and water, most likely via the concerted decomposition or disproportionation of the adsorbed molecular species. The bulk of the 2-iodoethanol decomposes at about 150 K via an initial carbon-iodine scission to form -O(H)CH2CH2- (similar to80%) and 2-hydroxyethyl (similar to20%) intermediates. Two competing reactions are involved with the subsequent conversion of the 2-hydroxyethyl species around 160 K, a reductive elimination with surface hydrogen to yield ethanol, and a beta-H elimination to surface vinyl alcohol. The -O(H)CH2CH2-, on the other hand, dehydrogenates to a -OCH2CH2- oxametallacycle species about the same temperature. Both 2-hydroxyethyl and the oxametallacycle species tautomerize to acetaldehyde, around 210 K and above 250 K, respectively, and some of that acetaldehyde desorbs, whereas the rest decomposes to hydrogen and carbon monoxide. The implications of this chemistry to catalysis are discussed.