Vapor liquid equilibrium (VLE) data were measured for the five binary systems comprising each of the unbranched constitutional isomers of a C-6 ester with n-octane at 60.0 kPa. All five systems exhibited strong positive deviations from ideality and minimum boiling azeotropes due to the fundamental differences in the intermolecular forces of each component in the pair, as well as the closeness of the pure component boiling points at the system pressure. Thermodynamic consistency of all data was shown using the Wisniak L/W and McDermott Ellis consistency tests, and the data were correlated and predicted with the NRTL and UNIFAC activity coefficient models, respectively. The data illustrated the role of the location of the polar ester functional group on the phase behavior of respective ester structural isomers with a common second component.