For 5-isopropyl tetrazole, which resembles the structure of a vinyl polymer with tetrazole pendants attached directly to the backbone, the pKa was found to be slightly higher (4.19) than for 5-isopropyl-tetrazole, which results in a lower degree of ionization a certain KOH concentration. However, the LUMO level of 5-isopropyl tetrazole in the neutral and deprotonated was -1.19 and 0.01 eV, respectively, which is considerably higher than that of the phenyl substituted analogue. It is also higher than what has been reported for the oxindole motif, which is known to show remarkable stability. This could further govern alkali resilience, but could not be experimentally verified for small molecule model systems due to the explosivity at such high N/C ratios. The LUMO isosurfaces of 5-isopropyl tetrazole in the neutral and deprotonated are shown in Figure .