Iodine atoms and iodomethane radical cations: Their formation in the pulse radiolysis of iodomethane in organic solvents, their complexes, and their reactivity with organic reductants. [Accelerated electrons]

Journal Article · Thu May 30 04:00:00 EDT 1991 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100164a045· OSTI ID:6011740

Shoute, L C.T.; Neta, P ^[1]

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1. National Inst. of Standards and Tech., Gaithersburg, MD (United States)

Pulse radiolysis of iodomethane in various organic solvents leads to formation of iodine atoms or iodomethane radical cations, which in turn form complexes with iodomethane or with the solvent. Radiolysis in cyclohexane gives CH{sub 3}I{center dot}I, which exhibits an absorption peak at 390 nm, whereas radiolysis in benzene forms the solvent complex, C{sub 6}H{sub 6}{center dot}I, which exhibits an intense broad absorption centered at 490 nm. Radiolysis of iodomethane in acetone, benzonitrile, and halogenated hydrocarbons results in formation of the radical cation CH{sub 3}I{sup +}. In the former two solvents, this species forms a complex with another molecule of iodomethane to give (CH{sub 3}I){sub 2}{sup +}, which absorbs at 420 nm, in agreement with previous results in aqueous solutions, but in halogenated hydrocarbons it forms complexes with the solvents, absorbing at 320-360 nm, i.e., near the absorption of monomeric CH{sub 3}I{sup {sm bullet}+} in water. Complexes of I atoms oxidize phenol and triphenylamine relatively slowly whereas complexes of CH{sub 3}I{sup {sm bullet}+} react more rapidly. The reactivity of the CH{sub 3}I{sup {sm bullet}+}{center dot}RX complexes increases in the order of RX = CH{sub 2}Cl{sub 2}, CHCl{sub 3}, CH{sub 2}Br{sub 2}, CCl{sub 4}, CH{sub 3}I, and for each complex the reactivity with phenol increases with increase in electron donating power of substituents. Replacing the methyl group of iodomethane radical cation with ethyl or isopropyl decreases the reactivity, whereas trifluoromethyl increases the reactivity. These oxidation reactions proceed via an intermediate complex between the iodine species and the organic reductant.

• OSTI ID: 6011740
• Journal Information: Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 95:11; ISSN 0022-3654; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400600* -- Radiation Chemistry
ABSORPTION SPECTROSCOPY
ACETONE
ALKANES
AMINES
AROMATICS
BENZENE
CATIONS
CHARGED PARTICLES
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
COMPLEXES
CYCLOALKANES
CYCLOHEXANE
DATA
DECOMPOSITION
ELEMENTS
EXPERIMENTAL DATA
HALOGENS
HYDROCARBONS
HYDROXY COMPOUNDS
INFORMATION
IODINE
IONS
KETONES
KINETICS
NONMETALS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC IODINE COMPOUNDS
ORGANIC SOLVENTS
OXIDATION
PHENOL
PHENOLS
RADIATION EFFECTS
RADICALS
RADIOLYSIS
REACTION INTERMEDIATES
REACTION KINETICS
SOLVENTS
SPECTRA
SPECTROSCOPY
VISIBLE SPECTRA