The formation and isomerization of 3-amino-2-butenenitrile (diacetonitrile) and its anion, followed by IR spectra, ab initio and DFT force field calculations

Abstract

The synthesis of 3-amino-2-butenenitrile (diacetonitrile) by base-catalyzed dimerization of acetonitrile was followed by IR spectra, ab initio HF, MP2 and DFT BLYP, B3LYP force field calculations, and correlation analysis. The conversion of diacetonitrile into the anion causes a 67 cm −1 decrease in the cyano stretching frequency, a threefold increase in the corresponding integrated intensity and other strong spectral changes. In agreement between theory and experiment, the isomerization takes place in the intermediate −NC(CH 3)CH 2CN→[HNC(CH 3)CHCN] − rather than in the end (protonation) product HNC(CH 3)CH 2CN→H 2NC(CH 3)CHCN, due to the essential energy difference between the charge-localized and delocalized anionic intermediates.