The theoretical enthalpies of formation (Delta(f)H degrees(298.15)) of methyl vinyl ketone (MVK, CH2=CHC(O)CH3) methacrolein (MACR, CH2=C(CH3)CHO), and the radical products formed in their corresponding OH radical oxidations have been calculated with DFT (MPW1K/6-31+G(d,p)) and multilevel (MCCM-UT-CCSD(T)//MPW1K/6-31+G(d,p)) methods. The bond dissociation energies (BDE, DH298.150) of the H-atoms that can be abstracted from the MVK and MACR molecules, and the C-0 forming bonds of the OH addition products are also calculated. The regioselectivity of the global reaction is discussed in terms of bond strength. (c) 2005 Elsevier B.V. All rights reserved.