Radiation-induced homolytic aromatic substitution. VI. The effect of metal ions on the hydroxylation of benzonitrile, anisole, and fluorobenzene

Journal Article · Thu Jun 02 00:00:00 EDT 1977 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100526a006· OSTI ID:7219929

Eberhardt, M K

The radiation-induced hydroxylation of benzonitrile, anisole, and fluorobenzene has been investigated. In absence of oxidizing agents (O/sub 2/, metal salts) only trace amounts of substituted phenols are formed. Some metal salts (Fe(CN)/sub 6//sup 3 -/, Fe/sup 3 +/, Cr/sub 2/O/sub 7//sup 2 -/) oxidize the intermediate hydroxycyclohexadienyl radicals and give a very high conversion of OH radicals to phenols, whose isomer distribution is dependent on the metal salts. With Cu/sup 2 +/ salts (Cu(ClO/sub 4/)/sub 2/, CuSO/sub 4/, CuCl/sub 2/) no oxidation of the hydroxycyanocyclohexadienyl radicals was observed. Oxidation with K/sub 3/Fe(CN)/sub 6/ leads in a quantitative way to the corresponding phenols. It was shown that in the hydroxylation of anisole, fluorobenzene, bromobenzene, toluene, benzonitrile, and nitrobenzene a linear relationship exists between log 2k/sub m//2k/sub 0/ + 2k/sub m/ + k/sub p/ and log k/sub p//k/sub m/ and sigma/sub M/ values. Electron-withdrawing substituents give a high percentage of meta hydroxylation, whereas electron-donating substituents give a low percentage of meta hydroxylation. As the difference in electron density between ortho and meta position increases the electrophilic OH radicals attack preferentially at the ortho and para positions. It was concluded that dehydration from the initially formed hydroxycyclohexadienyl radicals takes place only if the substituent is electron donating (+M effect), but not if the substituent is electron withdrawing (NO/sub 2/, CN).

• Research Organization: Puerto Rico Nuclear Center, San Juan
• OSTI ID: 7219929
• Journal Information: J. Phys. Chem.; (United States), Vol. 81:11
• Country of Publication: United States
• Language: English

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ANISOLE
CHEMICAL RADIATION EFFECTS
HYDROXYLATION
AROMATICS
FLUORINATED AROMATIC HYDROCARBONS
NITRILES
HYDROXYL RADICALS
CHEMISTRY
ETHERS
HALOGENATED AROMATIC HYDROCARBONS
ORGANIC COMPOUNDS
ORGANIC FLUORINE COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
RADIATION CHEMISTRY
RADIATION EFFECTS
RADICALS
400600* - Radiation Chemistry
400301 - Organic Chemistry- Chemical & Physicochemical Properties- (-1987)