Kinetics and absorption spectra of transients in the radiolysis of hexafluorobenzene in aqueous solution: A pulse radiolysis study

Journal Article · Thu Jan 14 04:00:00 EST 1993 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100104a019· OSTI ID:6486063

Shoute, L C.T.; Mittal, J P ^[1]

---

1. Bhabha Atomic Research Centre, Bombay (India)

Hexafluorobenzene reacts with hydrated electrons with a rate constant of 8.5 [times] 10[sup 9] M[sub [minus]1]s[sup [minus]1]. In alkaline solution, the radical anion formed has absorption maxima at 280 and 390 nm. The radical anion decays with a rate constant 2k = 4.6 [times] 10[sup 9] M[sup [minus]1]s[sup [minus]1] to form a carbanion which has absorption maxima at 290, 345, and 410 nm. Below pH 11, C[sub 6]F[sub 6][sup [sm bullet][minus]], is rapidly protonated to form cyclohexadienyl radical which has bands at 260 and 350 nm. The pK[sub a] of the C[sub 6]F[sub 6]H[sm bullet][r equilibrium] was estimated to be 12.4. The radical anion derived from ethanol also reduces C[sub 6]F[sub 6] with a rate constant of 2.5 [times] 10[sup 6] M[sup [minus]1] s[sup [minus]1], and the radical anion formed has absorption bands at 300 and 400 nm. It decays by radical recombination to yield a carbanion which has absorption bands at 310 and 580 nm. Both the radical anion and the carbanion formed display considerable inertness and have long lifetimes. The product spectrum shows evidence for the formation of long-chain molecules, indicating the involvement of anionic polymerization. Hydroxyl radical adds to hexafluorobenzene with a rate constant of 1.4 [times] 10[sup 9] M[sup [minus]1] s[sup [minus]1] to form an adduct, hydroxycyclohexadienyl radical, which has absorption bands at 280 and 400 nm. O[sup [sm bullet][minus]] adds to hexafluorobenzene with a rate constant of 9.4 [times] 10[sup 7] M[sup [minus]1] s[sup [minus]1]. The adduct undergoes base-catalyzed fluoride elimination to yield phenoxide radical which has absorption maxima at 300 and 430 nm. The adduct also undergoes acid-catalyzed water elimination at lower pH to yield C[sub 6]F[sub 6][sup [sm bullet]+], and the radical cation is also formed by electron-transfer reaction with SO[sub 4][sup [sm bullet][minus]]. 36 refs., 8 figs., 1 tab.

• OSTI ID: 6486063
• Journal Information: Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 97:2; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400600* -- Radiation Chemistry
ABSORPTION SPECTROSCOPY
ALCOHOLS
ANIONS
AQUEOUS SOLUTIONS
AROMATICS
CHARGED PARTICLES
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
DECOMPOSITION
DISPERSIONS
ELECTRON TRANSFER
ELECTRONS
ELEMENTARY PARTICLES
EQUILIBRIUM
ETHANOL
FERMIONS
FLUORINATED AROMATIC HYDROCARBONS
HALOGENATED AROMATIC HYDROCARBONS
HYDROXY COMPOUNDS
HYDROXYL RADICALS
IONS
KINETICS
LEPTONS
MIXTURES
ORGANIC COMPOUNDS
ORGANIC FLUORINE COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
PH VALUE
POLYMERIZATION
RADIATION EFFECTS
RADICALS
RADIOLYSIS
REACTION KINETICS
RECOMBINATION
SOLUTIONS
SOLVATED ELECTRONS
SPECTROSCOPY
TRANSIENTS