ChemInform Abstract: Formation of Radical Anions on the Reduction of Carbonyl-Containing Perfluoroaromatic Compounds in Aqueous Solution: A Pulse Radiolysis Study (original) (raw)
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The Journal of Physical Chemistry, 1996
Radical anions are formed on addition of hydrated electrons to pentafluoroacetophenone (PFA) and pentafluorobenzaldehyde (PFB) in aqueous solutions. On the other hand, addition of hydrated electrons to pentafluorobenzoic acid (PFBA) leads to rapid fluoride elimination. The spectrum of the radical anion of PFA has λ max at 300 and 440 nm with absorption coefficient at 440 nm 440 ) 2100 L mol -1 cm -1 . PFA •decays with a rate constant of (7 ( 3.0) × 10 3 s -1 . It has a pK a ) 7.5 and the spectrum of the conjugate acid has λ max at 270 and 460 nm with 460 ) 900 L mol -1 cm -1 . The spectrum of the radical anion of PFB has λ max at 285 and 430 nm with 430 ) 800 L mol -1 cm -1 . PFB •decays with a rate of (4 ( 2) × 10 3 s -1 . It has a pK a ) 7.2 and the spectrum of the conjugate acid has weak absorption at 330 nm. Evidence for the formation of the radical anion was obtained from intermolecular electron transfer from the radical anions of PFA and PFB to p-benzoquinone (Q), methyl viologen (MV 2+ ), and 9,10-anthraquinone-2-sulfonate (AQS -). Strong reductants derived from reduction of 2,2-bipyridine (BpyH • ) and 1,10-phenanthroline (PhenH • ) can reduce both PFA and PFB. From the kinetics of these electron transfer reactions the reduction potentials of PFA and PFB have been determined to be -0.86 ( 0.1 and -0.75 ( 0.1 V vs NHE at pH 9.4. Addition of OH • radical to the aromatic ring of these fluorinated compounds led to rapid HF elimination and the formation of phenoxyl radicals, and addition of H • atoms led to the formation of cyclohexadienyl radical. † Also affiliated with the Jawaharlal
Fluoride Elimination upon Reaction of Pentafluoroaniline with H, and OH Radicals in Aqueous Solution
The Journal of Physical Chemistry, 1996
Reduction of pentafluoroaniline (PFA) leads to rapid fluoride elimination to form the aminotetrafluorophenyl radical. This radical undergoes rapid intramolecular electron transfer from the amino group to the phenyl radical site and protonates at the latter site to form the tetrafluoroaniline radical cation or its deprotonated form (pK a ) 2.3). Oxidizing radicals such as SO 4
Journal of Fluorine Chemistry, 1999
The reactivity of persistent perfluoroalkyl radical, perfluoro-3-ethyl-2,4-dimethyl-3-pentyl (1), with various electron-donating reagents was investigated. It is revealed that 1 which is robust under oxidative conditions is rather vulnerable under reductive conditions. Thus, Lewis bases such as triethylamine and triphenylpnictogens (Ph3Pn, Pn=N, P, As, Sb, Bi) and some soft anions such as iodide or tetraphenyl borate reacted with 1 to give perfluoro-3-isopropyl-4-methylpent-2-ene (2) quantitatively. Even very weak Lewis bases such as diethyl ether and diethylsulfide also reacted with 1 to give 2 and additionally a hydrido product, perfluoro-3-ethyl-3-H-2,4-dimethylpentane (4). Hydrogen gas did not react with 1 at all without a catalyst, but in the presence of metal Pd adsorbed on charcoal, smoothly reacted to give 2 in quantitative yield. Metal hydrides such as LiAlH4, NaBH4, NaH, BH3 (THF complex), Bu3SnH, Me2PhSiH reacted with 1 to give 2 and 4. That an electron transfer mechanism is operating in the formation of 2 is obvious, but not conclusive in the formation of 4.
2006
"Perfluorodiacyl peroxides are an important class of perfluorinated peroxides. Thermal decompositions of selected perfluorinated peroxides have been analyzed in terms of stability of the radical products. In the temperature range of 0-90 °C, all these peroxides undergo first-order decomposition in diluted solutions. EPR analyses provide important information in order to prove the structure of the oncoming perfluorinated radicals. Correlations between thermal stability and radical structures have been supposed."
Environmental Science & Technology, 2006
Photochemical decomposition of persistent perfluorocarboxylic acids (PFCAs) in water by use of persulfate ion (S 2 O 8 2-) was examined to develop a technique to neutralize stationary sources of PFCAs. Photolysis of S 2 O 8 2produced highly oxidative sulfate radical anions (SO 4 •-), which efficiently decomposed perfluorooctanoic acid (PFOA) and other PFCAs bearing C 4-C 8 perfluoroalkyl groups. The major products were Fand CO 2 ; also, small amounts of PFCAs with shorter than initial chain lengths were detected in the reaction solution. PFOA at a concentration of 1.35 mM (typical of that in untreated wastewater after an emulsifying process in fluoropolymer manufacture) was completely decomposed by a photochemical system with 50 mM S 2 O 8 2and 4 h of irradiation from a 200-W xenonmercury lamp. The initial PFOA decomposition rate was 11 times higher than with photolysis alone. All sulfur-containing species in the reaction solution were eventually transformed to sulfate ions by this method. This method was successfully applied to the decomposition of perfluorononanoic acid contained in a floor wax solution.
Journal of Fluorine Chemistry, 1989
Electrochemical fluorination of N-cyclopentylpyrrolidine gave the corresponding Famine together with a ring-opened compound N-(F-pentyl)-Fpyrrolidine in the ratio of 1 to 1, in 55:; yield. N-cyclohexylpyrrolidine, N-cyclopentylpiperidine, and N-cyclohexylpiperidine were also electrochemically fluorinated in the same manner to give the corresponding Famines , their isomers with rearranged structures, and ring-opened ones, in the ratio of ca_ 4:2:1, 2:1:1, and 2:1:1, respectively in 51 to 53:; yields. Supporting spectral data are presented. substrates [6-91. This paper describes the synthesis of N-(F-cycloalkyl)-F-pyrrolidines and N-(F-cycloalkyl)-F-piperidines by electrochemical fluorination. 68 RESULTS AND DISCUSSION The substrates N-cyclopentylpyrrolidine (L), N-cyclohexylpyrrolidine (ZJ), N-cyclopentylpiperidine (J), and N-cyclohexylpiperidine (4) were synthesized from the corresponding cyclic amines (pyrrolidine and piperidine) and cyclic ketones (cyclopentanone and cyclohexanone) through a well-known enamine formation reaction followed by reduction with formic acid [lo]. Electrocheminal fluorinations of l-4 were conducted by the conventional way described elsewhere [5]. The electrochemical fluorination of these substrates proceeded smoothly and gave the crude fluorinated products in 74-78% yields when calculated assuming the products obtained were all desired. Since our concern is the preparation of perfluorochemicals useful as oxygen carriers, the fragmented products which have less carbon atoms than those of the starting substrates and the polyfluorinated or N-F bondcontaining products which often have a fatal toxicity were omitted from our study on the products. For our restricted purpose, the crude fluorination products were at first treated with a mixture of 8N aqueous sodium hydroxide and diisobutylamine to remove not-fully-fluorinated by-products and then with a potassium iodide-acetone solution to remove any contaminating nitrogen fluorides. After the treatment the yields of the perfluorinated products decreased to 51-55%. The perfluorinated product thus obtained was usually a mixture of the structural isomers so that the isolation of each component was difficult even by careful distillation using a spinning band included in Table V. Other minor components were not identified completely, but mass spectral and gas chromatographic data suggested the structures of N-(F-n-hexyl)-(F-methyl)-F-pyrrolidine (2.8%) and N-(F-methylpentyl)-(Fmethyl)-F-pyrrolidine (4.9%). The yields were all calculated from the peak areas.
Perfluoroorganoelement chemistry anticipating the 21st century
Journal of Fluorine Chemistry, 1999
On the basis of the de®nition of per¯uoroorganoelement compounds, their preparation and chemical reactions are described. The element displacement principle is developed and a periodic system of functional groups is provided. On this base R f E-and functional groups are de®ned as paraelements. Evidence for this new concepts are provided.