Differential scanning calorimetry and neutron diffraction have been used to characterize the mixing behavior of monolayers of binary linear alcohols adsorbed on a graphite surface from solution. Here we have investigated pairs of alcohols with alkyl chain lengths of C5-C11 and which differ in length by a single methylene group. If the shorter of the two alcohols is "odd", then the monolayers show essentially good or ideal mixing. In contrast, if the shorter of the two alcohols is "even", then a molecular compound is formed in the adsorbed layer.