Ab initio and DFT investigation of fluorinated methyl hydroperoxides: Structures, rotational barriers, and thermochemical properties

Ab initio and density functional theory (DFT) calculations have been performed on CH2FOOH, CHF2OOH, CF3OOH, CF2ClOOH, and CFCl2OOH. Geometries of stable conformers are optimized at the MP2(FULL)/6-31G(d,p) and B3LYP/6-31G(d,p) levels of theory. The enthalpies of formation (ΔHf,298°) and the ROOH, ROOH, and ROOH bond dissociation enthalpies (BDEs) are estimated for each of the studied hydroperoxides using the calculated reaction enthalpies (ΔHrxn,298°) of the adopted isodesmic reactions. The results show that the progressive fluorine substitution of hydrogen atoms in methyl group results in an increase in each of BDE(OH), BDE(OO), and BDE(CO). This has been explained in terms of the stabilizing influence of fluorine-substituted methyl groups. However, the replacement of F by Cl when going from CF3OOH to CFCl2OOH leads to a decrease in both BDE(OO) and BDE(CO). Potential energy barriers for internal rotation about CO and OO are calculated at the B3LYP/6-31G(d,p) level for each of the studied hydroperoxides.