Studies on the hyperfine interactions in the 1-ethyl-, 1-isopropyl-, and 1-tert-butyl-4-methoxycarbonylpyridinyl radicals

Hyperfine splitting contants for the 1-ethyl-, 1-isopropyl-, and 1-tert-butyl-4-methoxycarbonylpyridinyl radicals have been completely assigned and the substituent effects on the electron spin distribution have been discussed. Rotational barriers for the ethyl and isopropyl groups bonded to the ring nitrogen atom were determined from the temperature dependence of the splitting constants for the β protons, demonstrating the equilibrium conformations of the alkyl groups. These conformations are supported by theoretical calculations.