Isomerizational and conformational study of 3-fluorophenylamino-2-acetyl propenenitrile (FPAAPN)

Abstract

The isomers and conformers of push–pull 3-fluorophenylamino-2-acetyl propenenitrile (FH4C6)NHCHC(CN)(COCH3) (FPAAPN) have been studied experimentally by NMR and vibrational spectroscopy and theoretically by ab initio calculations at MP2 and DFT B3LYP levels in various basis sets. The IR and Raman spectra of FPAAPN as a solid and as a solute in various solvents have been recorded. The NMR spectra were obtained in chloroform, acetone, acetonitrile and dimethylsulfoxide at room temperature.FPAAPN was prepared as a pure Z-isomer with an intramolecular hydrogen bond. According to the NMR spectra in chloroform the studied compound exists as a single ZZa entity. On the other hand, in more polar solvents the isomerization process occured and an additional EZa confomer was detected. The influence of the environment polarity on this conformational equilibrium is discussed with respect to the SCRF solvent effect calculations using IEFPCM model.The observed IR and Raman bands were compared with calculated MP2/6-311G∗∗ harmonic vibrational frequencies and assigned on the basis of potential energy distribution.