Hydrogen bonding interaction between HO2 radical and selected organic acids, RCOOH (R = CH3, H, Cl and F)

A systematic study on the H-bonding interaction of hydroperoxyl radical with formic, acetic, chloroformic and fluoroformic acids has been carried out using B3LYP/6-311++G(2df,2p) and MP2/aug-cc-pVTZ methods. Several possible geometries have been considered, and the calculated global minima of RCOOH–HO2 have been found to be planar cyclic structure with two hydrogen bonds. A definite trend has been found between the electron donating character of the R group with calculated bond lengths, binding energies and vibrational frequencies. The most stable complex of RCOOH–HO2 with H2O has been found to be associated with a planar cyclic structure involving three hydrogen bonds.