Electronic structure and vibration spectrum of protonated semicarbazide

Abstract

Quantum chemical optimization of the geometrical parameters of the protonated form of semicarbazide [H₂NCONHNH₃]⁺ is performed in the MNDO/H approximation. Effective charges on atoms are calculated as well as bond orders, formation enthalpy, and the ionization potential. An inverse spectral problem is solved for the protonated form of semicarbazide and its deutero analog. Frequencies, potential energy distribution over vibrational degrees of freedom, and force constants are calculated. Assignments of frequencies to vibrations of atomic groups are given. It is shown that protonation of the semicarbazide molecule at the nitrogen atom of the hydrazine fragment leads to weakening of all bonds except for CO and CN bonds of the carbamide group.