Vibrational spectroscopy of 5-amino-3-methyl-4-isoxazolecarbohydrazide and its N-deuterated isotopologue

• The spectral characterization of 5-amino-3-methyl-4-isoxazolecarbohydrazide is presented.
• The conformational search has predicted six hypothetical structures of title compound which have been discussed.
• The detailed interpretation of vibrational spectra and assignments of fundamental frequencies (PED) is proposed on the basis of the calculated results.
• The N-deuterated isotopologue of 5-amino-3-methyl-4-isoxazolecarbohydrazide was synthesized to eliminate disturbing frequencies in carbonyl region of IR and Raman.
• The detailed NBO analysis has been done in order to explain the donors→acceptors interactions.

Both spectral and structural studies of 5-amino-3-methyl-4-isoxazolecarbohydrazide (HIX) were done and compared to calculated parameters using ab initio DFT methods. A detailed interpretation of the infrared and Raman spectra of title molecule is reported on the basis of the calculated potential energy distribution (PED). The conformational search for possible conformers and tautomers of title compound has been conducted and widely discussed. N-deuterated isotopologue of 5-amino-3-methyl-4-isoxazolecarbohydrazide (HIXD) was synthesized to eliminate disturbing frequencies in carbonyl region of IR and Raman. Besides, N-deutaration enabled the unambiguous assignment some bands to specific vibrations. Moreover, the stability of the 5-amino-3-methyl-4-isoxazolecarbohydrazide arising from hyper conjugative interactions has been studied using natural bond orbital (NBO) analysis.