To an NMR tube, the 4-nitrobenzaldehyde solution (0.572 mL), the DABCO solution (28.3 µL) and methyl acrylate (29.5 µL) were mixed, which gave a ratio of 1:0.94:0.3 (4-nitrobenzaldehyde/methyl acrylate/DABCO) and concentrations of 0.578 M, 0.543 M, and 0.173 M, respectively. The NMR tube was given a quick shake and measured at regular intervals. The internal standard (cyclohexane) could be used as a reference integral in each measurement, and the concentration of each species could be calculated.