Applications of ENDOR Spectroscopy to Radical Cations in Freon Matrices. Part 1. The radical cation of s‐trans‐buta‐1,3‐diene

Precise values of the proton coupling constants have been determined from the ENDOR spectra of the radical cation of s‐trans‐buta‐1,3‐diene generated from the neutral compound by γ irradiation in a CFCl3 matrix at 77 K. These values are 1.119 and 1.050 mT for the pairs of exo‐ and endo‐protons in the 1,4‐positions, respectively, and 0.283 mT for the pair of protons in the 2,3‐positions. A general TRIPLE resonance spectrum proves that all coupling constants have the same sign which should be negative by theory, Evidence by experiment and theory indicate that the s‐trans‐configuration of the neutral compound is retained upon ionization.