ELECTRONIC-STRUCTURE AND VIBRATION SPECTRUM OF PROTONATED SEMICARBAZIDE

Quantum chemical optimization of the geometrical parameters of the pro tonated 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 inve rse spectral problem is solved for the protonated form of semicarbazid e and its deutero analog. Frequencies, potential energy distribution o ver 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 nit rogen atom of the hydrazine fragment leads to weakening of all bonds e xcept for CO and CN bonds of the carbamide group.