The thermal and oxidative degradation behavior and the corrosiveness of imidazole (Im), 2-methylimidazole (2MIm), 2-ethyl-4-methylimidazole (2E4MIm), 2,4,5-trimethylimidazole (2,4,5MIm), and 1,2,4,5-tetramethylimidazole (1,2,4,5MIm) were investigated in a CO2 rich environment. The imidazoles demonstrated high thermal stability in all solutions; however, Im and 2MIm were corrosive. Polyalkylated imidazoles were less stable toward oxidation compared to Im. Rat cell (PC-12) toxicology screening of Im and 45 alkylated imidazoles showed reduced toxicity for polyalkylated imidazoles compared to Im. Cell viability correlated negatively with cLogP predictions when cLogP > 3. The high rate of oxidative degradation and formation of potentially carcinogenic degradation products will prevent the use of polyalkylated imidazoles in industrial processes directed toward CO2.