Two different organic surfaces were created by self-assembly (SA) of bifunctionalized monomers using OH-and COOH-terminated alkanethiols. X-ray photoelectron (XP) and soft X-ray absorption (NEXAFS) spectroscopy have been used to determine the chemical composition of and the molecular orientation in the SA monolayers adsorbed on Au substrates. Subsequently the two OH-and COOK-terminated organic surfaces were exposed to phenyl isocyanate (C6H5NCO,PIG) in order to investigate their chemical reactivity. In both cases the reactivity to gas-phase PIC was very low for the sample at room temperature. Reaction yields of more than 80% could, however, be achieved by depositing multilayers on a sample cooled down to 120 K which was subsequently warmed to 290 K.