Formation of radical cations of methoxylated benzenes by reaction with OH radicals, Ti$sup 2+$, Ag$sup 2+$, and SO$sub 4$$.$$sup -$ in aqueous solution. An optical and conductometric pulse radiolysis and in situ radiolysis electron spin resonance study

Journal Article · Mon Dec 01 00:00:00 EST 1975 · J. Phys. Chem., v. 79, no. 25, pp. 2773-2779

OSTI ID:4097062

O'Neill, P; Steenken, S; Schulte-Frohlinde, D

The reactions of anisole, 1,2-, 1.3-, and 1,4-dimethoxybenzene and 1,2,3- , 1,2,4-, and 1,3,5-trimethoxybenzene with Tl$sup 2+$, Ag$sup 2+$, SO$sub 4$$.$$sup -$, and OH, respectively, were investigated in aqueous solution using optical and conductometric pulse radiolysis and in situ radiolysis ESR for detection. Tl$sup 2+$ and Ag$sup 2+$ were produced by reaction of OH with Tl$sup +$ and Ag$sup +$, respectively. SO$sub 4$$.$$sup -$ was generated by reaction of e$sup -$/sub aq/ with persulfate. Tl$sup 2+$, Ag$sup 2+$, and SO$sub 4$$.$$sup -$ react with the methoxylated benzenes by electron transfer to yield radical cations and Tl$sup +$, Ag$sup +$, and SO$sub 4$$sup 2-$, respectively. In the absence of cyclohexadienyl radicals the radical cations decay by second-order kinetics with rate constants ranging from less than 4 x 10$sup 3$ to 1 x 10$sup 9$ M$sup -1$ sec$sup -1$ depending on the positions of the methoxy groups relative to each other. OH radicals react with the methoxylated benzenes by addition to the aromatic ring with diffusion-controlled rates. Depending on conditions, the hydroxycyclohexadienyl radicals thus formed subsequently undergo three different types of reaction: (a) bimolecular decay (k values ranging from 8 x 10$sup 8$ to 2 x 10$sup 9$ M$sup -1$ sec $sup 1$); (b) reaction with protons to yield radical cations (k values from 2 x 10$sup 8$ to 1.4 x 10$sup 9$ M$sup -1$ sec$sup -1$); and (c) reaction with radical cations (k values from 8.6 x 10$sup 8$ to 3.5 x 10$sup 9$ M$sup -1$ sec$sup -1$). The assignment of the optical absorption spectra of the radical cations and the determination of the respective extinction coefficients is based on a combination of optical and conductivity data. The radical cation yield obtained at pH 1 by reaction of protons with the OH adducts of the substrates amounts to greater than 90 percent in the case of anisole, 1,3- dimethoxybenzene, and 1,3,5-trimethoxybenzene. (auth)

• Research Organization: Max-Planck-Institut fuer Kohlenforschung, Muelheim, Ger.
• NSA Number: NSA-33-014320
• OSTI ID: 4097062
• Journal Information: J. Phys. Chem., v. 79, no. 25, pp. 2773-2779, Other Information: Orig. Receipt Date: 30-JUN-76
• Country of Publication: United States
• Language: English

Related Subjects

N40300* -Chemistry-Radiation Chemistry
400600* -Chemistry-Radiation Chemistry
*ANISOLE- CHEMICAL REACTIONS
*ETHERS- CHEMICAL REACTIONS
*HYDROXYL RADICALS- CHEMICAL REACTIONS
ANIONS
AQUEOUS SOLUTIONS
CATIONS
ELECTRON BEAMS
ELECTRON SPIN RESONANCE
MEV RANGE 01-10
PULSED IRRADIATION
RADIOLYSIS
SILVER COMPOUNDS
SOLVATED ELECTRONS
SULFATES
THALLIUM COMPOUNDS