Electron spin resonance of γ-irradiated malonic acid

Journal Article · Sat Jul 01 04:00:00 EDT 1961 · Molecular Physics

DOI:https://doi.org/10.1080/00268976100100481· OSTI ID:4833939

Horsfield, A.; Morton, J. R.; Whiffen, D. H.

The electron spin resonance spectrum of a gamma -irradiated single crystal of malonic acid indicated the presence of at least two chemically distinct radicals. The most stable radical is CH(CO/sub 2/H)/sub 2/, but the structure and orientation of the radical CH/sub 2/(CO/sub 2/H) was studied more extensively. The anisotropy of the spectra of this radical with respect to the direction of the main magnetic field H shows that the free radical carbon atom has gone over to planar sp/sup 2/ hybridization, the HCH angle being 116 deg plus or minus 5 deg . Since the two ends of the undamaged malonic acid molecule are distinguishable in the crystal, two sites were expected for the radical CH/ sub 2/(CO/sub 2/H). It appeared, however, that approximately 80% of the radicals occupy one site, and only about 20% the other. Comparison of the orientation of the main CH/sub 2/(CO/sub 2/H) radical with that of the undamaged molecule indicated that in the radical the plane of the CH/sub 2/ group is approximately perpendicular to the plane of the (CO/sub 2/H) group. The spectra of the less predominant CH/sub 2/(CO/sub 2/H) radicals were too weak and too overlapped for detailed analysis. Present information about the principal processes in the radiolysis of polyphenyl hydrocarbons is summarized and interpreted. The processes are considered to be: the dissociation of energized aromatic molecules into radicals and molecular products; the interaction of aryl radicals with aromatic hydrocarbons and themselves; the interaction of hydrogen atoms with aromatic hydrocarbons; and product formation by processes not involving hydrogen atoms or other radicals. The processes leading to the formation of polymer'' and the composition of this polymer'' are described. The effects on hydrogen yield and polymer'' yield of temperature change, phase. change, and change of radiation type, the linear energy transfer effect, are interpreted.

• Research Organization: National Physical Lab., Teddington, Middx., Eng.
• Sponsoring Organization: USDOE
• NSA Number: NSA-16-000232
• OSTI ID: 4833939
• Journal Information: Molecular Physics, Journal Name: Molecular Physics Journal Issue: 4 Vol. 4; ISSN 0026-8976
• Publisher: Taylor & Francis
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

ANISOTROPY
ATOMS
CARBON
CHEMISTRY
CRYSTALS
ELECTRONS
FREE RADICALS
GAMMA RADIATION
HYDRIDES
HYDROGEN
MAGNETIC FIELDS
MALONIC ACID
MOLECULES
ORGANIC ACIDS
RESONANCE
SPECTRA
SPIN
STABILITY