Figure 1. Optimized structures with atom numbering and relative energies (kcal mol-1in parenthesis, ZPE-corrected values) for the most important stationary points for the gas-phase reaction HN=CH2 + HCOOH¢ªH2N-CH2-COOH (1) computed at the B3LYP/6-31++G(d,p) level of theory.)