Thermal decomposition of diisopropyl peroxydicarbonate. CIDNP and product studies

The thermal decomposition of diisopropyl peroxydicarbonate (IPP) in two solvents (chlorobenzene and tetrachloroethylene) was studied by [¹H]NMR. In both solvents the major decomposition products, acetone and isopropanol, showed interesting CIDNP effects during the first few minutes of the decomposition at 60 and 75 respectively. For decomposition in the presence of excess di-t-butyl-p-cresol, no acetone was formed while the other CIDNP effects were completely suppressed. From these results and further analysis of the by-products, it is concluded that the observed CIDNP effects are closely connected with induced decomposition of IPP, starting by abstraction of the secondary H-atom of the isopropyl group.     

Nitrosation kinetics of phenolic components of foods and beverages

The kinetics of the reactions between sodium nitrite and phenol or m-, o-, or p-cresol in potassium hydrogen phthalate buffers of pH 2.5–5.7 were determined by integration of the monitored absorbance of the C-nitroso reaction products. At pH > 3, the dominant reaction was C-nitrosation through a mechanism that appears to consist of a diffusion-controlled attack on the nitrosatable substrate by NO⁺/NO₂H₂⁺ ions followed by a slow proton transfer step; the latter step is supported by the observation of basic catalysis by the buffer which does not form alternative nitrosating agents as nitrosyl compounds. The catalytic coefficients of both anionic forms of the buffer have been determined. The observed order of substrate reactivities (o-cresol ≈ m-cresol > phenol ≫ p-cresol) is explained by the hyperconjugative effect of the methyl group in o- and m-cresol, and by its blocking the para position in p-cresol. Analysis of a plot of ΔH^# against ΔS^# shows that the reaction with p-cresol differs from those with o- and m-cresol as regards the formation and decomposition of the transition state. The genotoxicity of nitrosatable phenols is compared with their reactivity with NO⁺/NO₂H₂⁺. © 1997 John Wiley & Sons, Inc.     

Pyrolytic hydrolysis of polycarbonate in the presence of earth-alkali oxides and hydroxides

The rise in the use of polycarbonate (PC) calls for the development of after-use treatments. In this work, we describe a process for obtaining bisphenol A (BPA), phenol and isopropenyl phenol (IPP) from PC by hydrolysis at temperatures between 300 and 500 °C. The experiments were carried out in a steam atmosphere in the presence of MgO, CaO, Mg(OH)₂ or Ca(OH)₂ as catalysts, respectively. The results were compared with the hydrolysis of PC in the absence of any catalysts. All of these catalysts accelerated the hydrolysis of PC drastically, with MgO and Mg(OH)₂ being more effective than their Ca counterparts. The differences between oxides and hydroxides were negligible indicating the same mechanism for both, oxides and hydroxides. BPA was the main product at 300 °C, with a yield of 78% obtained in the presence of MgO. At 500 °C, BPA was mainly degraded to phenol and isopropenyl phenol (IPP). It can be shown that a combined process involving PC hydrolysis at 300 °C and BPA fission at 500 °C leads to high yields of phenol and IPP and the drastic decrease of residue.     

活性酯固化邻甲酚环氧树脂反应机理的研究

采用交叉反应研究在促进剂2-甲基咪唑存在下活性酯固化邻甲酚环氧树脂的反 应机理，用傅立叶转换红外（FTIR）原位测量技术，NMR，气-质联用（GC-MS）等 手段研究了模型化合物的反应动力学，并提出了其反应机理。结果表明，在促进剂 2-甲基咪唑存在下活性酯固化邻甲酚环氧树脂的反应是通过分子内机理进行的。     

Kinetics and mechanism of p-isopropenylphenol synthesis via hydrothermal cleavage of bisphenol A

Although bishydroxyarylalkanes are known to be reactive in high-temperature (T > 200 degrees C) liquid water (HTW), no mechanistic insight has been given to explain the reactivity of methylene bridge-containing diaryls under hydrothermal conditions. We examined the kinetics and mechanism of p-isopropenylphenol (IPP) synthesis via bisphenol A (BPA) cleavage in HTW. The cleavage reaction is first order in BPA. Cleavage of BPA in HTW occurs by specific acid catalysis, by specific base catalysis, and by general water catalysis. Under neutral conditions, the dominant mechanism is general base catalysis with water serving as the proton acceptor. We generated a detailed chemical kinetics model for the decomposition reaction based on a base-catalyzed mechanism in the literature. This three-parameter model fit the experimental data for BPA disappearance and formation of IPP and phenol and accurately predicted the yield of the IPP hydrolysis product acetone. Using acid- and base-catalyzed mechanisms, we explain the reactivity in HTW reported for other diaryl groups linked by methylene bridges and propose criteria for assessing the reactivity of methylene bridges under hydrothermal conditions.     

Dipole moment characterization of phenol–, o-cresol–, and p-cresol–formaldehyde resins

Dipole moments and their temperature dependence have been measured in p-dioxane for fractionated novolac phenol–, o-cresol–, and p-cresol–formaldehyde polymers. The phenol–formaldehyde fractions covered a molecular weight range of 200 to 6100, and the limiting dipole moment ratio 〈μ²〉/xm² is 1.48. The p-cresol–formaldehyde dipole-moment ratio at a DP of 4 is 2.47, whereas the phenol–formaldehyde dipole-moment ratio is 1.40. That for o-cresol–formaldehyde is intermediate in value. The dipole-moment temperature coefficients are positive for p-cresol chains and negative for the phenol–formaldehyde chains. These results indicate that the hydroxyl groups along the p-cresol–formaldehyde polymer are highly ordered, with the aromatic rings closer to the sterically hindered planar position than in the phenol–formaldehyde polymers.     

Conversion of anisole in the presence of methanol over AlPO4?Al2O3 catalysts modified with fluoride and sulfate anions

The gas-phase microcatalytic conversion of anisole in the presence of methanol (methanol/anisole molar ratio=4) was studied at temperatures ranging from 523 to 673 K over anion treated (1–3 wt.% F or SO ₄ ^2– ) AlPO₄–Al₂O₃ (25 wt.% Al₂O₃) catalysts. Anisole conversion gave a mixture of dealkylated and C-alkylated products (C-alkylation preferentially in ortho-position) where dealkylation always predominates. The influences of the reaction temperature and both anion type and anion loading upon the conversion of anisole and the selectivities of the products were investigated. The higher increase in surface acidity by fluoride loading increases both the C-alkylation selectivity (mainly to 2-methylanisole) and dealkylation to phenol; so that a lower anisole conversion (smaller pseudokinetic constant) and higher methylanisoles selectivity is found for APAI-P-F catalysts related to unmodified one.     

Kinetics of reaction of methyl α-eleostearate with phenol

The kinetics of addition reactions between methyl α-eleostearate which forms the main chain of tung oil and phenol when catalyzed by an acid, p-toluene sulfonic acid, have been studied. The addition reactions, carried out with phenol was shown to be second order with regard to methyl α-eleostearate concentration and first order with regard to phenol concentration. The reactions were additions of two phenol molecules to one methyl α-eleostearate molecule, and it was presumed that they proceed in the two steps given below in which the first step is rate determining: ((1)) ((2)) The apparent reaction rate constant (l/mol min) was found to be 0.036 and its value was nearly equal to that in the case of m-cresol. The apparent activation energie (kcal/mol) was found to be 4.76 and its value was larger than that in the case of m-cresol.     

Amperometric Phenol Biosensor Based on Horseradish Peroxidase Entrapped PVF and PPy Composite Film Coated GC Electrode

Polyvinylferrocene (PVF) was used as a mediator for the fabrication of a horseradish peroxidase (HRP)-modified electrode to detect phenol derivatives via a composite polymeric matrix of conducting polypyrrole (PPy). Through an electropolymerization process, enzyme HRP was entrapped with PPy in a three-electrode system onto a glassy carbon electrode previously covered with PVF, resulting in a composite polymeric matrix. Steady-state amperometric measurements were performed at ?200 mV vs. Ag/AgCl in aqueous phosphate buffer containing NaCl 0.1 M (pH 6.8) in the presence of hydrogen peroxide. The response of the HRP-modified PVF electrode was investigated for various phenol derivatives, which were 4-chlorophenol, phenol, catechol, hydroquinone, 2-aminophenol, pyrogallol, m-cresol, and 4-methoxyphenol. Analytical parameters for the fabricated PVF electrode were obtained from the calibration curves. The highest sensitivity was obtained from the calibration of 4-chlorophenol as 29.91 nA/μM. The lowest detection limit was found to be 0.22 μM (S/N?=?3) for catechol, and the highest detection limit was found to be 0.79 μM (S/N?=?3) for 4-methoxyphenol among the tested derivatives. The biosensor can reach 95% of steady-state current in about 5 min. The electrode is stable for 2 months at 4 °C.     

Alkylation of phenol with dimethyl carbonate over AlPO4, Al2O3 and AlPO4-Al2O3 catalysts

The vapor-phase catalytic alkylation of phenol with dimethyl carbonate over different AlPO₄ (Al/P=1), Al₂O₃ and AlPO₄-Al₂O₃ (5–25 wt.% Al₂O₃) catalysts produces anisole (O-alkylation) as the major reaction product althougho-cresol (C-alkylation) and methylanisoles were also found. The reaction is first order in phenol while O-and C-alkylation follow parallel processes. As compared with methanol, DMC is far more effective as a methylating agent, and the methylation proceeds at a lower temperature and with higher O-alkylation selectivity.     

Long-chain double SO3H-functionalized Brønsted acidic ionic liquids catalyzed selective alkylation of phenol and p-cresol with tert-butanol

A simple, efficient, and selective approach for the tert-butylation of phenol and p-cresol using two double SO₃H-functionalized long-chain Brønsted acidic ionic liquids as recyclable catalysts is reported. Under optimum reaction conditions, 89.4% conversion of the phenol and 73.7% selectivity of 2,4-tert-butyl-phenol and 93.2% conversion of the p-cresol and 89.2% selectivity of 2-tert-butyl-p-cresol were obtained. Two ionic liquids could be recovered readily and their catalytic activity almost completely retained after five recycles.     

A green and sensitive method to determine phenols in water and wastewater samples using an aqueous two-phase system

A greener and more sensitive spectrophotometric procedure has been developed for the determination of phenol and o-cresol that exploits an aqueous two-phase system (ATPS) using a liquid-liquid extraction technique. An ATPS is formed mostly by water and does not require organic solvent. Other ATPS components used in this study were the polymer, polyethylene oxide, and some salts (i.e., Li₂SO₄, Na₂SO₄ or K₂HPO₄ + KOH). The method is based on the reaction between phenol, sodium nitroprusside (NPS) and hydroxylamine hydrochloride (HL) in an alkaline medium (pH 12.0), producing the complex anion [Fe₂(CN)₁₀]¹⁰⁻ that spontaneously concentrates in the top phase of the system. The linear range was 1.50-500 μg kg⁻¹ (R ≥ 0.9997; n = 8) with coefficients of variation equal to 0.38% for phenol and 0.30% for o-cresol (n = 5). The method yielded limits of detection (LODs) of 1.27 and 1.88 μg kg⁻¹ and limits of quantification (LOQs) of 4.22 and 6.28 μg kg⁻¹ for phenol and o-cresol, respectively. Recoveries between 95.7% and 107% were obtained for the determination of phenol in natural water and wastewater samples. In addition, excellent agreement was observed between this new ATPS method and the standard 4-aminoantipyrine (4-AAP) method.     

Synthesis,characterization and epoxidation of hexakis-4-(2-(4-((β-methallyl)oxy)phenyl)propan-2-yl)phenoxycyclotriphosphazene

4-(2-(4-((β-Methallyl)oxy)phenyl)propan-2-yl)phenol was prepared via the reaction of methallyl chloride with bisphenol A and used for the synthesis of hexakis-4-(2-(4-((β-methallyl)oxy)phenyl)propan-2-yl)phenoxycyclotriphosphazene. It was revealed that the latter undergoes the Claisen rearrangement and can be also epoxidized by 3-chloroperbenzoic acid. The obtained epoxide was cured by a treatment with isophorone diamine. The decomposition and glass transition temperatures of cured resin were also estimated (275 and 130?°C, respectively) by DSC and TGA methods.     

Ultrasound-assisted derivatization of phenolic compounds in spiked water samples before pervaporation, gas chromatographic separation, and flame lonization detection

Summary A fully automated method, based on continuous ultrasound-assisted derivatization coupled with pervaporation before gas chromatographic separation and flame ionization detection, has been developed for the determination of phenol and cresols in water. Spiked water samples were doped with acetic anhydride and dipotassium hydrogen phosphate, before introduction into the flow system, to achieve catalytic acetylation of the target compounds. A multivariate study was performed to optimize the main factors affecting the derivatization process. The correlation coefficients, r, of the calibration plots obtained were better than 0.999 for cresols and better than 0.99 for phenol. Detection limits were 0.02 μg mL¹ for phenol, o-cresol, andp-cresol, and 0.05 μg mL¹ form-cresol. Reproducibility and repeatability, expressed as relative standard deviation, ranged from 2.0–3.9% and from 1.0–3.5% respectively.     

Human urine certified reference material CZ 6010: creatinine and toluene metabolites (hippuric acid and o-cresol) and a benzene metabolite (phenol)

A reference material for the biological monitoring of occupational exposure to toluene, benzene and phenol was prepared. O-cresol and hippuric acid (metabolites of toluene) are used for the biological monitoring of occupational exposure to toluene. Phenol, a metabolite of benzene, is used for the biological monitoring of exposure to benzene, but phenol can of course also be used as an indicator of exposure to phenol as well. The reference material (RM) used for the determination of these metabolites was prepared by freeze-drying pooled urine samples obtained from healthy persons occupationally exposed to toluene and those taking part in an inhalation experiment. Tests for homogeneity and stability were performed by determining urine concentrations of o-cresol, hippuric acid, creatinine and phenol. To investigate the stability of the RM, the urinary concentrations of o-cresol and phenol were monitored for eighteen months using GC and HPLC, while those of hippuric acid and creatinine were followed for five and six years, respectively, using HPLC. Analysis of variance showed that the concentrations did not change. The certified concentration values (and their uncertainties) of the substances in this reference material (phenol concentration c=6.46±0.58 mg l⁻¹; o-cresol concentration c=1.17±0.15 mg l⁻¹; hippuric acid concentration c=1328±30 mg l⁻¹; creatinine concentration c=0.82±0.10 g l⁻¹) were evaluated via the interactive statistical programme IPECA.     

Determination of Phenol in Surface Waters by High-Performance Liquid Chromatography with Sorption Preconcentration

The retention of phenol and its derivatives on Silasorb C₈ and PepRPC ^TMHR 5/5 was studied. Both columns are suitable for the separation of pyrocatechol–phenol–o-cresol(p-cresol)–2,6-xylenol mixtures using mobile phases containing 10–20 vol % of isopropanol and 1% glacial acetic acid in water. A procedure was developed for determining phenol with a detection limit of 4 mg/L (acetonitrile; signal-to-noise ratio, 2; loop volume, 25 L). With preconcentration from 1-L samples in a Diapak-phenol/P cartridge, the procedure allows phenol to be determined in water samples with a detection limit of 4 g/L. The procedure was used in analyses of samples of river and tap water.     

P-HZSM-5催化剂上合成对异丙基苯酚的研究

研究了在Ｐ－ＨＺＳＭ－５ 上苯酚与异丙醇烷基化合成对异丙基苯酚（ｐ－ＩＰＰ）的反应, 考察了磷含量对催化反应性能的影响, 用ＮＨ３－ＴＰＤ和Ｐｙｒ－ＩＲ表征了Ｐ－ＨＺＳＭ－５ 的表面酸性质． 结果表明, 磷改性ＨＺＳＭ－５ 可提高ｐ－ＩＰＰ选择性（达９５％ ）, 而降低了苯酚的转化率, 并导致酸量减少和酸强度减弱． 磷与分子筛的相互作用引起了分子筛脱铝． 焙烧温度对活性和选择性均有影响． 分子筛在９７３ Ｋ、Ｐ－ＨＺＳＭ－５ 在８２３ Ｋ焙烧时, ｐ－ＩＰＰ选择性最高     

Physico-Chemical Studies on the Interaction of Surface Active Substances at the Dropping Mercury Electrode in Pulsating Field

The tensammetric measurements indicated an appreciable interaction of o-cresol with piperidine as well as with triethanolamine in aqueous media. The sharp discontinuities in the mixtures of o-cresol + piperidine and o-cresol + triethanolamine at the mole ratio 3:1 for o-cresol to amine are observed by tensammetric, conductommetric and high frequency measurements. The shift of peak potential as well as increase in the magnitude of peak of the mixture have been utilized in determining the composition of the complexes by tensammetric measurements. The nature of formation of such complexes has been predicted. The nature of such interactions have been investigated by infra-red studies. The molar ratio of phenol to amine (piperidine and triethanolamine) are also estimated to be 3:1.     

Generation and synthetic uses of stable 4-[2-isopropylidene]-phenol carbocation from bisphenol A

[reaction: see text] Stable 4-[2-isopropylidene]-phenol carbocation, IPP cation 1, was generated readily by addition of bisphenol A in concentrated sulfuric acid at ambient temperature, and the cation could be used for facile syntheses of 4-isopropenyl phenol (IPP), IPP dimers, and spiro-bisphenol derivatives.     

On the compatibility of the IPP/PA6/EPDM blends with and without functionalized IPP I. Thermo-oxidative behaviour

Binary isotactic polypropylene (IPP)/polyamide 6 (PA6) and ternary IPP/PA6/ethylene–propylene diene terpolymer (EPDM) blends in various ratios were obtained in a Haake Rheocord mixer. Processing behaviour was changed in the presence of IPP functionalized with bismaleimide (BMI), maleic anhydride (MA) and acrylic acid (AA) as reactive compatibilizing agents. The thermal and thermo-oxidative behaviour of blends was studied by differential scanning calorimetry and thermogravimetry. The functionalized IPPs modify the crystallinity degree and the decomposition behaviour of both IPP and PA6 as a result of chemical reactions of functional groups with those of the PA6. The changes depend on the IPP/PA6 or IPP/PA6/EPDM ratio, the chemical nature and amount of the functionalized IPP. On the basis of the processing and thermal data one can conclude that the compatibilizing agent effect increases in the following order: IPP-AA 相似文献