An ESR study of the CH2ClCȮ radical at 77 K in x-irradiated chloroacetamide crystals

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Abstract
X‐irradiation of chloroacetamide crystals at 77 K yields at least two radicals which are not stable near 300 K. One of these give rise to a four line ESR spectrum due to two nonequivalent protons with the principal hyperfine tensor components for H (1) equal to 268.4, 260.3, and 256.1 MHz and for H (2) equal to 129.9, 109.7, and 109.9 MHz. The principal g values are gmax=2.0674, gint=2.0144, and gmin=1.9909. Comparing the corresponding direction cosines to selected molecular directions obtained from an x‐ray crystal structure as well as deuteration studies suggests the species to be the π‐radical CH2ClCȮ. The unpaired electron is largely distributed between the oxygen and carbon 2p orbitals whose symmetry axis lies perpendicular to the CCO plane. Crystallographically, the chlorine atom lies nearly in the CCO plane and does not give rise to any resolvable ESR hyperfine couplings. The second radical gives rise to a complex ESR spectrum which has been tentatively assigned as due to ⋅CH2Cl. This radical decays upon warming above 100 K with the resultant formation of ĊHClCONH2.

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