An in situ infrared spectroelectrochemical technique based upon the thin layer ATR optical configuration was used to examine the potential induced reorientation of ethylene carbonate (EC) at a Au(110) electrode. The behavior of EC was studied in aqueous solutions containing HClO4, NaClO4 and tetramethylammonium perchlorate electrolytes. Intense absorption bands due to the carbonyl and ring vibrational modes of EC were observed in the 1900-925 cm(-1) region. The carbonyl and ring vibrational modes are clearly influenced by the An electrode and subsequently were frequency shifted; however, they did not show any potential dependent frequency behavior. Other bands did exhibit potential dependency. In addition, the magnitudes of some EC bands shift depending on the nature of the electrolyte cation. The spectral bands associated with the electrolyte provided evidence of ion migration in the diffuse double layer under the applied electric field.