Photoaccelerated oxidation of chlorinated phenols

Exposure to visible light increases the rate of oxidation of chlorinated phenols by hydrogen peroxide in aqueous solution in either the presence or the absence of iron-based catalysts, which may be explained by the aqueous photoreactions of chloroquinone intermediates.     

Raman spectral analysis of phenoxyacetic acid and some chloro substituted phenoxyacetic acids

Raman spectra of phenoxyacetic acid and chlorine substituted phenoxyacetic acids viz., o-chlorophenoxyacetic acid, p-chlorophenoxyacetic acid and 2,6-dichlorophenoxyacetic acid have been analysed with the aid of abinitio theoretical calculations. The effect of chlorine substituents on the Raman spectra of phenoxyacetic acid have also been analysed by considering some important vibrational modes.     

Gas-phase radiation-chemical formation of dioxins from chlorinated phenols

The gas-phase radiation-chemical formation of dioxins from chlorinated phenols in the electron-beam removal of toxic impurities from industrial gases is considered. A kinetic model of the process is proposed. Conditions under which the efficiency of removal of the above compounds from gases significantly decreases were determined with the use of this model. The results of a numerical simulation are compared with currently available experimental data.     

Characteristics of phenol and chlorinated phenols sorption onto surfactant-modified bentonite

Surfactant-modified bentonite was synthesized by replacing adsorbed Na+ with long-chain alkyl quaternary ammonium cation, hexadecyltrimethylammonium bromide (HDTMAB). The sorption isotherms of phenol, p-chlorophenol, and 2,4-dichlorophenol were modeled according to the Langmuir and Freundlich equations. The Langmuir isotherm was found to describe the equilibrium adsorption data well. The mechanisms and characteristics of sorption of these ionizable organic contaminants onto surfactant-modified bentonite from water were investigated systematically and described quantitatively. The sorption properties are affected by the treatment conditions, such as amount of organobentonite, and the properties of organic compounds. Results indicated that adsorption of phenols from water was in proportion to their hydrophobicities, which increased with chlorine addition (phenol相似文献   

Determination of chlorinated phenols in surface-treated lumber by HPLC

A solution of internal standard in acetonitrile is used to extract samples of wood from lumber which had been commercially treated with chlorinated phenols. The tetrachlorophenol(TCP) and pentachlorophenol( PCP) were analytically separated from each other and from the other wood extractive compounds using a high performance liquid chromatograph (HPLC). The ultraviolet (UV) absorptions of the TCP, PCP, and internal standard were automatically measured as they eluted. The UV absorption peaks were integrated, and the amounts of TCP and PCP present were calculated with a dedicated microcomputer. Compared with the method previously used, this method is faster (up to 144 samples per 48 hours), has the same accuracy and precision, and it is linear over the concentration range used.     

Facile O-arylation of phenols and carboxylic acids

[reaction: see text] A facile, transition-metal-free O-arylation procedure for phenols and aromatic carboxylic acids has been developed that affords good to excellent yields of arylated products under very mild reaction conditions. A methoxy-substituted aryl triflate affords O-arylated products in high yields with excellent regioselectivity. This chemistry tolerates a variety of functional groups.     

Electroanalytical chemistry of chlorinated phenols at a glassy carbon electrode

The electroanalytical chemistry of chlorinated phenols at a glassy carbon electrode in various solvent—electrolyte media is described. Differential pulse voltammetry may be used to determine chlorinated phenols in a methanol—0.07 M sulfuric acid medium. The determination of pentachlorophenol in liquid formulations is described. Cyclic voltammetric Studies are used to investigate the electrochemical reaction mechanisms of chlorinated phenols. The electrochemical oxidation products of these compounds are quite reactive, and follow-up chemical reactions result in electrode filming under the conditions studied.     

Substituent and solvent effects on electronic spectra of some substituted phenoxyacetic acids

The effects of substituents and solvents have been studied through the absorption spectra of nearly 19 para- and ortho-substituted phenoxyacetic acids in the range of 200-400 nm. The effects of substituent on the absorption spectra of compounds under present investigation are interpreted by correlation of absorption frequencies with simple and extended Hammett equations. Effect of solvent polarity and hydrogen bonding on the absorption spectra are interpreted by means of Kamlet equation and the results are discussed.     

Transalkylation of phenols over heteropoly acids

Transalkylation of 2,6-di-tert-butyl-4-R-phenols over solid heteropoly acids (H₃PW₁₂O₄₀, H₄SiW₁₂O₄₀, H₃PW₁₂O₄₀/SiO₂, H₄SiW₁₂O₄₀/SiO₂) in the presence of toluene or o-xylene as acceptors of a tert-butyl group at 100–140 °C produces 4-R-phenols with 92–98% yield (R = H, alkyl, aryl, etc.). HPAs are effective catalysts for the transalkylation of p-cresol and 2, 6-ditert-butyl-4-methylphenol.

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2,6----4-R- (H₃PW₁₂O₄₀, H₄SiW₁₂O₄₀, H₃PW₁₂O₄₀/SiO₂, H₄SiW₁₂O₄₀/SiO₂) 0- - 100–140°C 4-R- 92–98% (R = H, , ..). - 2,6----4-.

     

The surprisingly facile thermal dehalogenation of chlorinated aromatics by a hydroaromatic donor solvent. Tautomerization of chlorinated phenols and anilines

Up to 600 K, chlorinated benzenes and naphthalenes are inert in a hydrogen atom donating solvent such as 9,10-dihydroanthracene. However, when a hydroxyl or amine group is attached to the 2 or 4 position relative to chlorine, a surprisingly facile and selective hydrodehalogenation occurs at temperatures between 530 and 630 K. These features are the result of the onset of tautomeric equilibria for the chlorophenols or -anilines, creating the corresponding enones or imines, respectively, as reactive intermediates. The mechanism of dehalogenation involves the rate-determining transfer of a hydrogen atom from the solvent to the reactive intermediate according to a reverse radical disproportionation (RRD), followed by elimination of chlorine. The reactivity of mono- and dichlorophenols, chloroanilines, 4-chloro-1-naphthol, and 4-chloro-1-naphthylamine dissolved in 9,10-dihydroanthracene has been investigated. By means of density functional theory (DFT) calculations, the energies for the tautomers and their hydrogen affinities have been established. The experimental selectivities could be adequately reproduced by the computed data.     

S-benzylthiouronium salts of some carboxylic acids,sulfonic acids,and phenols

116 S-Benzylthiouronium suits have been prepared and were, if possible, checked by titration with perchloric acid in glacial acetic acid on a semi-micro scale. Out of these, 110 are salts of carboxylic acids, 2 of snlfonic acids, and 4 of nitrophenols. The melting points determined according to a standard procedure are given.     

Synthesis and transformations of unsaturated carboxylic acids

Summary A new method was developed for synthesizing diene -keto acids and their esters based on available furylacetylenic -glycols.For Communication 1 of this series see Izv. AN SSSR, Otd. Khim. Nauk, 1512 (1960).     

Flow-injection chemiluminescence determination of chlorinated isocyanuric acids

A rapid and sensitive flow-injection chemiluminescence method is described for the determination of dichloro- and trichloroisocyanuric acids based on the chemiluminescence produced during their reaction with luminol in alkaline medium. The effects of analytical and flow-injection variables on these chemiluminescence systems and determination of both oxidants are discussed. The optimized method yielded 3sigma detection limits of 8x10(-8) and 5x10(-8) mol L(-1) for the sodium dichloroisocyanurate and trichloroisocyanuric acid, respectively. The optimum conditions were found to be as follows: NaOH, 1x10(-1) mol L(-1); luminol, 5x10(-3) mol L(-1); KI, 2x10(-3) mol L(-1) and flow rate, 3.5 mL min(-1).     

Gas chromatographic determination of chlorinated phenols in the form of various derivatives

Derivatization of chlorophenols prior to gas chromatographic analysis resulted in a significant improvement of their chromatographic behaviour. Chlorophenols in the form of anisoles, acetates, and pentafluorobenzyl ethers were separated either on a HP-1 wide-bore capillary column or on a capillary column coated with a film of SE-54. Due to an enhancement of the poor electron-capture detection response of mono- and dichlorophenols, pentafluorobenzylation made it possible to determine trace amounts in spiked water. Moreover, simultaneous analysis of phenoxyalkanoic acids was accomplished under the same conditions.     

Alkylation of p-substituted phenols by heteropoly acids

Liquid-phase alkylation of p-tert-butylphenol (TBP) and p-cresol by olefins and benzyl chloride in the presence of solid heteropoly acids (HPA) H₃PW₁₂O₄₀ and 25% H₃PW₁₂O₄₀/SiO₂ at 100–150°C provides high yields of mono- and disubstituted products. HPAs are more active than H₂SO₄, easily separated from the reaction mixture and can be used repeatedly. -- () - () H₃PW₁₂O₄₀ 25% H₃PW₁₂O₄₀/SiO₂ 100–150°C - - . , H₂SO₄, - - .