Surface pressure-molecular area (pi-A) isotherms for monolayers of a new amphiphilic Schiff base, (octadecylamino)dihydroxysalicylaldehyde (ODADS), at an air/water interface were simulated by the molecular dynamics (MD) method for the first time. Potential energy, torsional angles, and hydration of the polar headgroups under periodic boundary conditions (PBC) have been used for this study. Hydration was done by a stacked array of water molecules relaxing under these boundary conditions. The simulations were carried out in a hexagonal lattice with the spatial PBC constraints in order to avoid clustering of the water molecules. The resulting isotherm with the transitions seen in the pi-A isotherm are explained from the potential energy plots for various surface densities.