A low-temperature scanning tunneling microscopy (LT-STM) study of four slightly different hydrocarbons based on hexaphenylbenzene (HPB) and hexa-peri-hexabenzocoronene (HBC) on the Cu(111) surface at submonolayer coverage is presented. All molecules show a commensurate monolayer structure, with significant differences in structure and growth mode. We find that the long range order and the size of defect free domains increase when the intermolecular interaction becomes stronger with respect to the molecule-substrate interaction. Moreover, we can assign adsorption and self-ordering properties to the different chemical groups within the molecules.