A quantum-chemical study of nitroguanidine and tetramethyl nitroguanidine: Stable structures, force fields, and the interpretation of the vibrational spectrum

Stable structures of nitroguanidine and tetramethyl nitroguanidine were searched by the MP2 and B3LYP methods with the use of the 6–31G(d,p) and 6–311G(d,p) basis sets. For nitroguanidine, the force fields calculated by these methods were scaled using the experimental spectra for seven isotopomers. The obtained scaling factors made it possible to theoretically evaluate and assign the frequencies in the spectrum of tetramethyl nitroguanidine.