Intramolecular hydrogen bonding in 2-nitromalonaldehyde: Infrared spectrum and quantum chemical calculations

To investigate the effect of NO2 group on the hydrogen bond strength, the charge distributions, steric effects, and electron delocalization in NO2MA and MA were studied by the Natural Bond Orbital (NBO) method for optimized model compounds at B3LYP/6-311++G** level of theory. The results of NBO analysis indicate that the electron-withdrawing effect of NO2 group decreases the hydrogen bond strength, but the steric and resonance effects increase the strength of the bond.