Acetic acid monomer, dimer and its deuterated analogue have been studied using ab initio Car-Parrinello molecular dynamics (CPMD). Full geometry optimization has been carried out in the gas phase in order to obtain minimum structures and hydrogen bonding properties. The results show a good agreement with the available experimental data. Infrared spectrum has been calculated and comparative vibrational analysis has been performed. CPMD vibrational results appear to be in a qualitative agreement with the experimental ones. (C) 2009 Elsevier B. V. All rights reserved.