Role of defects in radiation chemistry of crystalline organic materials. 2. Effective and selective formation of solute radicals and its dependence on the carbon-chain difference in the radiolysis products of C sub m H sub 2m+2 /C sub 10 D sub 22 normal hydrocarbon mixed crystals as studied by ESR spectroscopy

Journal Article · Thu Jan 11 04:00:00 EST 1990 · Journal of Physical Chemistry; (USA)

DOI:https://doi.org/10.1021/j100364a070· OSTI ID:6946464

Muto, Hachizo; Nunome, Keichi; Fukaya, Mitsuharu ^[1]

---

1. Government Industrial Research Institute, Nagoya (Japan)

Radiolysis of the mixed crystals of binary n-alkanes has been studied by ESR spectroscopy to understand the role of defects in the radical formation in crystalline organic compounds. Highly efficient (10-25%) and selective formation of solute radicals depending on the carbon-chain difference between solute and matrix molecules was found in the C{sub m}H{sub 2m+2} (1 mol %)/C{sub 10}D{sub 22} mixed crystals (m = 7-12) irradiated at 77 K. The terminal type of radical C{sup {center dot}}H{sub 2}CH{sub 2}CH{sub 2}- (I) is formed only in the mixed crystals with shorter solute molecules than the matrix (m < 10) and is the only solute radical in the case of m {le} 8. Penultimate type, CH{sub 3}C{sup {center dot}}HCH{sub 2}- (II), and interior type, -CH{sub 2}C{sup {center dot}}HCH{sub 2}- (III), of radicals are formed selectively in the case of m {ge} 10. These efficient and selective formations were observed neither in the mixed crystals irradiated at 4 K nor in the protiated-alkane matrix (C{sub 10}H{sub 22}) irradiated at 77 or 4 K. These results suggest that the D-atom reaction in the molecular layer boundary regions plays an important role in the solute radical formation. The details of this process are as follows. Deuterium atoms radiolytically produced from the matrix molecules can diffuse at 77 K, and some of them escape to the boundary regions. The escaped D atoms can migrate for some distance in the boundary regions (with looser molecular packings than those in the bulk regions) and efficiently abstract a H atom from a protiated solute molecule via a tunneling reaction with a large isotope effect. In the case of m {le} 8, the escaped D atoms can react with only the terminal CH{sub 3} groups of the solute molecule in the boundary regions, forming selectively radical I.

• OSTI ID: 6946464
• Journal Information: Journal of Physical Chemistry; (USA), Journal Name: Journal of Physical Chemistry; (USA) Vol. 94:1; ISSN 0022-3654; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400201 -- Chemical &amp; Physicochemical Properties
400600* -- Radiation Chemistry
ALKANES
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTIONS
CHEMISTRY
CRYSTALS
DATA
DATA ANALYSIS
DECOMPOSITION
ELECTRON SPIN RESONANCE
EXPERIMENTAL DATA
HYDROCARBONS
INFORMATION
ISOTOPE EFFECTS
MAGNETIC RESONANCE
MEASURING INSTRUMENTS
MEASURING METHODS
NUMERICAL DATA
ORGANIC COMPOUNDS
PRODUCTION
RADIATION CHEMISTRY
RADIATION EFFECTS
RADICALS
RADIOLYSIS
RESONANCE