Electron spin resonance of free radicals and radical pairs in irradiated single crystal of 1-methyluracil

Journal Article · Sat Sep 01 04:00:00 EDT 1973 · Z. Naturforsch., c, v. 28c, no. 9/10, pp. 523-532

OSTI ID:4329762

Flossmann, W; Huettermann, J; Mueller, A; Westhof, E

Radical formation by irradiation with x rays in single crystals of 1- methyluracil was measured using E SR spectroscopy at 9.5 GHz and 35 GHz. When irradiating and measuring at 77 deg K, radicals characterized by hydrogen abstraction from the methyl group were found to predominate. For the hyperfine splittings values of 8.5, 18.2, and 30.5 G were found for both alpha -protons and 3.3, 2.4, and 1.7 G for the (N1)-splitting. Pairs of abstraction radicals were also found under these conditions, showing quintet splittings of about 10 G and anisotropic dipolar coupling. Average distances parallel to c of 6.3 and 6.5 A were found for two types of pairs, while those perpendicular to c were not analyzed in detail. On irradiating and measuring at room temperature, an additional sextet pattern was found in the spectrum and attributed to a radical formed by addition of hydrogen at C(5). For the hyperfine splittings values of 8.1, 17.5, and 30.0 G were found for the alpha -proton and 31.2, 34.4, and 34.1 G for the two equivalent BETA -protons. Radical concentrations were determined at 77 deg K yielding about 90% abstraction radical, 15% of these in pairs and 10% of additional radical. About half of the abstraction radicals are convented to additional radicals between 200 and 280 deg K. The latter disappear at about 460 deg K, leaving a fraction of abstraction radicals which is annealed at even higher temperatures. (GE)

• Research Organization: Regensburg Univ., Ger.
• NSA Number: NSA-29-026689
• OSTI ID: 4329762
• Journal Information: Z. Naturforsch., c, v. 28c, no. 9/10, pp. 523-532, Journal Name: Z. Naturforsch., c, v. 28c, no. 9/10, pp. 523-532; ISSN ZNFCA
• Country of Publication: Germany
• Language: English

Related Subjects

*RADICALS-- ELECTRON SPIN RESONANCE
*URACILS-- RADIATION CHEMISTRY
COUPLING CONSTANTS
LOW TEMPERATURE
MONOCRYSTALS
N40300* --Chemistry--Radiation Chemistry
PHOTON BEAMS
SPECTRA
TEMPERATURE DEPENDENCE
X RADIATION