Abstract

The IR spectral of a series of 6 phenylnitroethenes (PNE) and 6 phenylnitropropenes (PNP) were assigned, based on a normal coordinates calculation performed on styrene and styrene-d8. Some frequencies were sensitive to the electronic properties of the substituents, and others to the substitution on Cbeta. AMI minimum energy conformations and rotational barriers around the C1-Calpha bond were calculated. According to these calculations, PNE are planar and PNP display an angle of 45-degrees between the ethylenic and aromatic planes. AM1 underestimates the height of the electronic barriers, which is however modulated by the electron donor properties of the substituent on the ring. A correlation between the calculated electronic barrier and the C=C ethylenic stretching frequency was observed.