Experimental and theoretical spectroscopic and electronic properties enriched with NBO analysis for 1-methyl-3-nitropyrazole and 1-methyl-5-nitropyrazole

• Experiment: IR, Raman, 1H, 13C, 1H1H, 1H13C NMR and reduction potential measurements.
• The full anharmonic IR spectra for the fundamentals, overtones and combination bands are presented.
• Detailed PED assignment for 1-methyl-3-nitropyrazole and 1-methyl-5-nitropyrazole is reported.
• Detailed NBO analysis has been done in order to explain the donors → acceptors interaction.
• The stability arising from hyper conjugative interaction is demonstrated.

Both experimental and calculated spectral and electronic properties of two isomers 1-methyl-3-nitropyrazole and 1-methyl-5-nitropyrazole have been demonstrated and discussed in details based on normal mode analysis. The fully anharmonic infrared spectra with calculated anharmonic intensities for fundamental bands, overtones and combination bands were also reported. The stability of title molecules arising from hyper conjugative interaction have been demonstrated using natural bond orbital (NBO) analysis. Electron affinities clearly point that 1-methyl-5-nitropyrazole should be much more susceptible to reduction process than 1-methyl-3-nitropyrazole what has been experimentally confirmed by measurement of reduction potential. For 1-methyl-5-nitropyrazole, unambiguous assignment of values of proton and carbon chemical shifts to appropriate protons and carbons has been made thanks to full analysis of 1H and 13C NMR spectra and two dimensional (2D) 1H1H and 1H13C NMR COSY spectroscopy.

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