Structure Determination of the 1,4-Cycloadduct Quenched after the High-pressure Reaction of Tetracyanoethylene with Styrene and Its Derivatives

The electronic, 13C NMR, 1H NMR, and IR spectra of the 1,4-cycloadducts of TCNE with styrene, styrene-α-d1, p-chlorostyrene, p-methylstyrene, α-methylstyrene, and 1,1-diphenylethylene were taken at low temperatures at 1 bar after the high-pressure reaction; the 13C NMR spectra were of decisive importance in determining the structure; the other kinds of spectra were consistent with the established structure. They have an electronic absorption band around 320 nm, which is assigned to the π-π* transition of the triene system in the adducts. Neither cis- nor trans-stilbene, which have a lower ionization potential, provides the 1,4-cycloadduct even at high pressure.