This paper investigates the reaction steps involved in tribochemical wear of SiO2 surfaces ill humid ambient conditions and the mechanism of wear prevention due to alcohol adsorption. The friction and wear behaviors of SiO2 were tested in three distinct gaeseous environments at room temperature: dry argon, argon with 50% relative humididy (RH), and argon with n-pentanol vapor pressure 50% relative to the saturation pressure (P/P-sat). Adsorbed gas molecules have significant chemical influences oil the wear of the surface. The SiO2 surface wears more readily in humid ambient compared to the dry case; however, it does not show any measurable wear in 50% P/P-sat n-pentanol vapor at the same nominal contact load tested in the dry and humid environments. The tribochemical wear of the SiO2 surface can be considered the Si-O-Si bond cleavage upon reactions with the impinging vapor molecules under tribological stress. DFT calculations were used to estimate the apparent activation energy needed to cleave the Si-O-Si bond at beta-cristobalite (111) and alpha-quartz (001) surfaces by reactions with impinging water and alcohol vapor molecules. The alkoxide termination of the SiO2 surfaces increases the energy barrier required to cleave the Si-O-Si bonds when compared to hydroxyl-terminated SiO2 surfaces.