19 F NMR spectra of compounds were collected on a Nanalysis NMReady 60PRO 60 MHz benchtop spectrometer. A stock solution of 0.1 M 5-fluorouracil with 0.02 M sodium trifluoromethanesulfonate was prepared with anhydrous N-methylpyrrolidinone (NMP), and was added to a NMR tube. Sodium trifluoromethanesulfonate was chosen as an internal standard due to its non-volatility and distinct chemical shift. Hexyl isocyanate (29.1 μL, 0.105 mmol) was added, and the NMR tube was placed in a heated water bath with periodic reaction monitoring every 30 minutes until 180 minutes. All NMR tubes were sealed using teflon tape and parafilm.