The mechanistic details on formation of HEGly and HEPO in MEA degradation are studied using the ab initio and density functional theory methods. The energetics of various pathways leading to formation of HEGly and HEPO are investigated. The addition of glyoxalic acid to MEA and simultaneous proton transfer results in a carbinolamine intermediate. This intermediate undergoes dehydration to generate zwitterion or imine. The hydrogenation of the resulting imine or zwitterion to form HEGly is found to be the rate determining step of the reaction.