Mechanisms for hydroxide radicals reacting with 2,3-epoxy-1,4-butanediol (BEPOX) and 2-methyl-2,3-epoxy-1,4-butanediol (β-IEPOX) in the gas phase are investigated using quantum chemistry computations. Geometries of all the structures are optimized at the X3LYP/6-31+g(d,p) level. The ground-state energy for each structure is then refined at the CCSD(T)/6-31+g(d,p) level. All possible reaction paths for BEPOX and β-IEPOX are analyzed. The results show that during BEPOX and β-IEPOX gas phase reactions, hydrogen abstractions on CchainH are the most energetically favorable reaction paths (S3, S7) while the addition reactions (S6, S9) are not likely to occur. The present theoretical study is consistent with previous experimental results. © 2013 Wiley Periodicals, Inc.