Criegee Intermediates Significantly Reduce Atmospheric (CF₃)₂CFCN

Sulfur hexafluoride (SF₆) is widely used for many industrial purposes due to its superior insulating properties; however, it is also a potent greenhouse gas with a high global warming potential (GWP) and an atmospheric lifetime of approximately 3,200 years. Here, we investigate heptafluoroisobutyronitrile ((CF₃)₂CFCN, also called C4-fluoronitrile or C4-FN) to help determine if it is a sustainable alternative to SF₆. We present experimental measurements and high-level quantum chemical calculations with a new computational strategy to elucidate the reaction kinetics between C4-FN and Criegee intermediates (CIs), specifically CH₂OO and syn-CH₃CHOO. By employing a new strategy to obtain CCSDT(Q)/CBS-level accuracy for a larger system than has previously been possible, combined with state-of-the-art kinetics methods, we obtain good agreement between theoretical and experimental rate constants. We find that the reactions between C4-FN and CIs are substantially faster than previously known degradation pathways, particularly the OH radical reaction. This shows the importance of incorporating additional reactive species into atmospheric chemistry models and climate impact assessments, paving the way for more effective climate change mitigation. Including the CI reactions in two possible scenarios gives a predicted atmospheric lifetime of C4-FN of 2-34.5 years, with a significant reduction in its global warming potential.