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The structural stability of monolayers formed by the self-assembly of mercaptoethanol (HOCH2CHr SH) at annealed, mica-supported gold (ME/Au) has been characterized using electrochemical, infrared spectroscopic, and X-ray photoelectron spectroscopic techniques. The study was motivated by the observation that the one-electron reductive desorption of long-chain n-alkanethiolatee by linear sweep voltammetry generally exhibits asingle well-defined wave,' while that of ME/Au produces two waves. The relative magnitudes of the waves for ME/Au are dependent on the extent of exposure to the laboratory ambient. Electrochemical oxidation of ME/Au shows that three oxidative processes occur sequentially. In the fmt process, MEVAu is catalytically oxidized by a four-electron process to a eulfidoacetic acid monolayer (adsorbed mercaptoacetic acid, MAA/Au). In the second process, the electrogenerated MAA/Au undergoes C-S bond cleavage, which gives rise to the second reductive desorption wave. In this case, as the extent of oxidation increases, a third desorption wave is also produced as a result of gradual formation of adsorbed polysulfur species. In the third oxidative process, the remaining sulfur monolayer is oxidatively desorbed from the surface. Our results, coupled with earlier literature reporta,*G2 s that electrochemical oxidation of thiolatea on gold is a multipath process with the favored path d e p e y z i on the reaction conditione and the chemical composition of the thiolate. The spontaneous oxidation of MEVAu may proceed via the same path as the electrochemical oxidation

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