Figure 3: Relationship between the energy of pyrrol-2-yl carbaldehyde (2) and rotation angle ϕ (pyrrole ring – carbonyl group). The most stable syn and anti conformers differ in the spatial arrangement of the carbonyl group about the inverting single bond (C-C). The calculations were performed at the B3LYP/6- 311++G(d,p) level of theory. 360° scanning of the dihedral angle N-C-C=O was performed with an increment of 5°.