“…This idea will be shown on the example of 3-aminopropenal (3-aminoacrolein), which has four conformers. The N-H⋯O hydrogen bond energy in the ZZ conformer of 3-aminoacrolein was quite often estimated [ 47 , 61 , 63 , 64 , 65 ], but the methods used did not take into account changes in the values of geometric parameters when switching from the bound system (ZZ-3-aminoacrolein) to reference forms (in particular, to ZE-3-aminoacrolein) [ 64 , 65 ]. The specific system of conjugated double bonds and, hence, the presence of four conformers (see Figure 9 ), allowed for proposing a method that was derived from the analysis of the mutual energy relations between the four conformers of 3-aminoacrolein ( Figure 9 ) [ 47 ].…”