Finally, it is clear when looking at the relationship between C4H partial atomic charge and stability colored by R3 substituent (Figure ) that NCBs with an R3 methyl substituent have higher stability than those with only hydrogen at that position. While examining NCBs with similar C4H partial charges, those with b at R3 demonstrate greater stability. Furthermore, our eleven most stable NCBs have a methyl substituent at the R3 position. Tan et al. hypothesized that this improved stability is due to kinetic effects, and we are still able to replicate this trend even though our analysis is strictly thermodynamic. This observation could be caused by additional steric effects, such as lower flexibility in the 1,4-dihydropyridine ring with greater congestion at the C5 carbon with a methyl substituent rather than a hydrogen.