31 P Hyperfine interaction in a new type of phosphorus‐containing iminoxy free radicals. An ESR study

Iminoxy radicals of a new type, having the general formula RC(NO ˙ )P(O)(OEt) 2 , were synthesized and characterized by means of ESR spectroscopy. The presence of two isomers due to the different position of the CNO˙ fragment with respect to the R substituent and the P atom, and the relative stability of the isomers, was established. The influence of the R substituent on the relative population of the isomers was found. The nitrogen hyperfine constants for the isomers differ by about 10%, while the phosphorus hyperfine constant for the less populated isomer is about six time greater, reaching a value of 60 G. A linear correlation was found between the values of this hyperfine constant and Dimroth–Reichardt E T (30)solvent parameters. The solvent dependence of the 31 P hyperfine constant was shown to be stronger than the dependence found for the 14 N hyperfine constant of nitroxides and iminoxyls.