Infrared spectra,vibrational assignment and ab initio calculations for 2,2,2-trifluoroethanimidamide

The infrared spectra of gaseous and solid 2,2,2-trifluoroethanimidamide, CF₃(NH₂)C=NH, have been recorded from 4000 to 80 cm^–1. A vibrational assignment for the normal modes is proposed based on group frequencies and normal coordinate calculations utilizing C₁ symmetry. The structures for both the cis hydrogen atom of the =NH group is cis to the NH₂ group] and trans geometric isomers have been determined from ab initio Hartree-Fock gradient calculations employing the GAUSSIAN-82 program with the 3–21G basis set. The most stable conformer at this level of calculation is found to be a C₁, structure with a partially rotated CF₃ group and the hydrogen atom of the imine group trans to the NH₂ group. The calculated structural parameters have only very small differences between the conformers. Barriers to internal rotation for the NH₂ and CF₃ groups and vibrational frequencies have been calculated for the C₁ form. The results of this investigation are compared with similar data on some corresponding molecules.Taken in part from the thesis of T. G. Sheehan which was submitted to the Department of Chemistry in partial fulfillment of the Ph.D. degree, May 1990.