THE MOLECULAR ZEEMAN EFFECT IN 2-CYCLOPENTANE-1-ONE, 2-PYRONE, AND 4-PYRONE

Abstract

The molecular Zeeman effect in several similar ring compounds has been studied. In 2-cyclopentene-1-one this yielded the Zeeman parameters of $g_{aa} = -0.088\pm 0.002, {g}_{bb} = -0.050\pm 0.001, {g}_{cc} = -0.006\pm 0.001$; and $2\chi_{aa}-\chi_{bb}-\chi_{cc} = 27.50\pm 1.70, -\chi_{aa}+2\chi_{bb} = 9.96\pm 1.70$. The magnetic susceptibility values given here and below are in units of $10^{-6}$ erg/G$^{2}$. mole. It was necessary to assign the microwave spectra of 2-pyrone before the Zeeman work could be undertaken. This resulted in rotational constants of A = 5677.64$\pm$0.02 MHz, B = 2882.24$\pm$0.01 MHz, and C = 1912.13$\pm$0.01MHz. The magnetic susceptibility anisotropies for a 2-pyrone are $2\chi_{aa}-\chi_{bb}-\chi_{cc} = 20.93\pm 1.97, -\chi_{aa}+2\chi_{bb}-\chi_{cc} = 28.15\pm 2.02$; and for 4-pyrone are $2\chi_{aa}-\chi_{bb}-\chi_{cc} = 16.15 \pm 2.80, \chi_{aa}+2\chi_{bb}-\chi_{cc} = 27.29\pm 3.99$. The magnetic susceptibility anisotropies in these and other molecules are considered in light of the relative stabilities of isomers as determined by other methods.