The properties of self assembled monolayers (SAMs) of 3-hexylthiophene, 2-mercapto 3-hexylthiophene and 2-mercapto 4-hexylthiophene on gold substrates have been evaluated by electrochemical techniques. It was observed that the 2-mercapto 4-hexylthiophene formed better packed films than the other molecules. As SAMs find potential applications in molecular electronics, the study, using tailored molecules, provides a better understanding of the film properties and the relation to the molecular structures.