Vibrational assignment and structure of 4-amino-3-cyano-3-penten-2-one

Fourier transform infrared and Fourier transform Raman spectra of 4-amino-3-cyano-3-penten-2-one and its deuterated analogue have been obtained. Density functional theory (DFT) B3LYP and G96LYP calculations have been carried out with the purpose of understanding the vibrational spectra of this compound and its deuterated analogue. Vibrational wavenumbers calculated by B3LYP/6-31G* (with a p shell added on the amine protons) force field are closed with the experimental results. The percentage of deviation of the bond lengths and bond angles gives a good picture of the normal modes, and serves as a basis for the assignment of the wavenumbers. The calculated geometrical parameters show a strong intramolecular hydrogen bond with a N...O distance of 2.605-2.622 Angstrom. This bond length is about 0.04-0.06 Angstrom shorter than that in its parent, 4-amino-3-penten-2-one (with no cyano substitution in the alpha-position). Experimental evidences also indicate presence of an intermolecular hydrogen bond in the solid state, completely, and in solution, partially. (C) 2002 Elsevier Science B.V. All rights reserved.