Rapid Access of Some Chloro‐substituted Isocoumarins and Biological Activity Toward Some Pathogenic Systems

Sulphuric acid–catalyzed chloralhydrate condensation with different m‐substituted benzoic acids formed trichlorophthalides 1, from which Zn+AcOH reduction afforded various dichloro derivatives 2. These derivatives 2 on treatment with alkaline Hg(OAc)₂+I₂ furnished different substituted isocoumarins 4.     

甲醛在CeO2(111)表面吸附的密度泛函理论研究

采用基于第一性原理的密度泛函理论和周期平板模型, 研究了甲醛在以桥氧为端面的CeO2(111)稳定表面上的吸附行为. 通过对不同覆盖度, 不同吸附位的甲醛吸附构型、吸附能及电子态密度的分析发现, 甲醛在CeO2(111)表面存在化学吸附与物理吸附两种情况. 化学吸附结构中甲醛的碳、氧原子分别与表面的氧、铈原子发生相互作用, 形成CH2O2物种; 吸附能随着覆盖度的增加而减小. 与自由甲醛分子相比, 物理吸附的甲醛构型变化不大, 其吸附能较小. 利用CNEB(climbing nudged elastic band)方法计算了甲醛在CeO2(111)表面的初步解离反应活化能(约1.71 eV), 远高于甲醛脱附能垒, 这与甲醛在清洁CeO2(111)表面程序升温脱附实验中产物主要为甲醛的结果相一致.     

A fluorescent dosimeter for formaldehyde determination using the Nash reagent in silica gel beads

Based on the Nash reagent embedded in silica gel beads as a recognition element, a fluorescent dosimeter for formaldehyde determination is established. The system can act as a fluorescent off–on switch for the qualitative detection of formaldehyde. The fluorescence emission of the Nash reagent-loaded silica gel beads is “switches off” (or very low) before exposure to formaldehyde, while fluorescence can be switched on when the beads are contacted with formaldehyde. The slope of fluorescence time scan spectra changes with formaldehyde concentration, which constitutes the basis of quantitative determination of formaldehyde concentration. The formaldehyde can also be semi-quantitatively measured in a naked-eye-detectable fashion. No response of this dosimeter to primary alcohols, ketones and other common substances was observed. The dosimeter is sensitive, inexpensive, a disposable, and simple in operation.     

Differential-pulse voltammetric determination of trace formaldehyde using magnetic microspheres and magnetic electrode

A new type of magnetic polymer microsphere containing acylhydrazine groups on the surface was synthesized. They can be reacted with formaldehyde to produce an electroactive adduct. Reduction of these derivatives following aggregation on a magnetic electrode is possible and is effective in the indirect determination of formaldehyde. The experimental conditions and electrode structure are discussed. Under the optimum conditions, it was found that the peak potential (Ep) of formaldehyde is -1.01 V (vs. Ag/AgCl). Formaldehyde in the range 1-1000 micrograms l-1 can be determined. The detection limit for formaldehyde is 0.3 microgram l-1 and the relative standard deviation for the determination of 100 micrograms l-1 formaldehyde was 2.26%. The method was applied to the determination of formaldehyde in environmental samples with satisfactory results.     

Bioremediation Potential of Formaldehyde by the Marine Microalga <Emphasis Type="Italic">Nannochloropsis oculata</Emphasis> ST-3 Strain

The present work is intended to investigate biodegradation of formaldehyde by the marine microalga Nannochloropsis oculata ST-3 strain. Formaldehyde concentration in the medium decreased with the growth of the ST-3 strain. It is observed that the degradation of formaldehyde concentration depends on the increased cell number of the ST-3 strain. The ST-3 strain which was adapted to formaldehyde stepwise was able to tolerate to 19.9 ppm formaldehyde and degrade 99.3% of it in the medium for 22 days. Tolerance and degradation ability of formaldehyde by the ST-3 strain was improved by stepwise increasing of the formaldehyde concentration. Transformation of [¹³C]formaldehyde in the medium with the passage of incubation was monitored by using a nuclear magnetic resonance (NMR) spectrometer. Formaldehyde was transformed into formate, and these two substances degraded in the medium with the passage of incubation as clearly shown by the NMR spectrum.     

Development of an Advanced Process for Manufacturing Polyacetal Resin

Abstract

An advanced process for manufacturing polyacetal resin has been developed. First, a new technology for the production of highly concentrated aqueous formaldehyde was developed by oxidizing methylal. Whereas the oxidation of methanol yields 1 mol water per mole formaldehyde, methylal oxidation produces only 1 mol water for every 3 mol formaldehyde. Thus, the output from methylal oxidation is more than 70% formaldehyde, compared with 55% from methanol oxidation. Second, a new extraction distillation process for formaldehyde purification was developed in order to get highly purified formaldehyde directly from formalin. By using highly purified formaldehyde, an end-capped polymer was obtained in the presence of acetic anhydride as a chain transfer or end-capping agent during polymerization. Third, the relatively high formaldehyde concentration enhances the formation of trioxane. Purified trioxane is copolymerized with ethylene oxide in the presence of an end-capping agent to get an end-capped polymer with high thermal stability. Two new intermediates from the initiation reaction of the copolymerization, 1,3,5,7-tetraoxacyclononane (TOCN) and 1,3,5,7,10-pentaoxacyclododecane (POCD), were isolated, and a new initiation mechanism was proposed. Fourth, the world's first acetal block copolymer was commercialized by the polymerization of formaldehyde in the presence of a lubricant functional polymer having an active hydrogen atom. This acetal block copolymer exhibits super lubrication properties.     

柱前衍生-萃取阻断反应-高效液相色谱法测定化妆品中游离甲醛

建立了柱前衍生化-萃取阻断反应-高效液相色谱(HPLC)测定化妆品中甲醛的方法。化妆品中甲醛检测的难点是: 甲醛缓释剂类防腐剂在衍生过程中释放甲醛,影响游离甲醛的准确测定。以2,4-二硝基苯肼(DNPH)乙腈溶液-磷酸盐缓冲液(pH 2)(1:1, v/v)为提取溶液,于室温下快速衍生2 min后,立即加入二氯甲烷萃取,阻断衍生反应,经乙腈稀释后进行HPLC测定。以Agilent C18柱(250 mm×4.6 mm, 5 μm)为分离柱,乙腈-水(60:40, v/v)为流动相,流速为1.0 mL/min,于355 nm波长下检测。在洗发水、乳液、膏霜、洗手液、牙膏、指甲油、粉饼中分别添加50、100、500、1000 μg/g 4个浓度水平的甲醛,其回收率为81%～106%,相对标准偏差(n=6)＜5.0%。方法的定量限(以信噪比(S/N)＞10计)为50 μg/g。该方法快速、简便、重现性好,且可以有效避免甲醛缓释剂类防腐剂分解释放甲醛,适用于化妆品中游离甲醛的测定。     

Quantitative Analysis of Formaldehyde Using UV‐VIS Spectrophotometer Pattern Recognition and Artificial Neural Networks

Abstract

This study is focused on the quantitative analysis of formaldehyde in aqueous solution using a Fluoral‐P reagent and describes the characterization of the reaction, including the effect of reagent concentrations, pH, response time, dynamic range, reproducibility, photostability, and selectivity by using an ultraviolet‐visible (UV‐VIS) spectrophotometer. The relative standard deviation value was 1.79 to 2.12%. The dynamic range of the complex gives a linear stimulation of 0.00 to 3.60 ppm for the concentration of formaldehyde. The reproducibility of this study is high, with 1.79 and 2.12% for 20 and 40 ppm of formaldehyde, respectively. The interference from acetaldehyde (formaldehyde: acetaldehyde=1:100) was lower than 2.10%. In addition, the application of artificial neural networks to quantitative analysis for formaldehyde has also been done in this study to optimize the dynamic range of formaldehyde involved in the formation of Fluoral‐P–formaldehyde complex. A three‐layer feed‐forward network and the back propagation algorithm‐operated training process were used in this study. For quantitative analysis of formaldehyde, artificial neural networks, networking with 23 hidden neurons and 40,000 cycle numbers with 0.001% learning rate, produce the best training results, with sum‐squared error value 0.5847.     

Spectrophotometric determination of formaldehyde by using formaldehyde dehydrogenase

A new method for the determination of formaldehyde by using formaldehyde dehydrogenase is described. The method is based on the quantitative oxidation of formaldehyde with oxidized nicotinamide adenine dinucleotide (NAD⁺), in the presence of formaldehyde dehydrogenase, to form the reduced dinucleotide (NADH). This enzyme does not require glutathione as a co-factor and the NADH produced, which is directly proportional to the concentration of formaldehyde in the assay solution, is then measured spectrophotometrically at 340 nm. Formaldehyde can be determined in the range 0.3–8.0 μg ml^?1 (1.0×10^?5–2.7× 10^?4 M) with a sensitivity of 0.216 absorbance/ μg ml^?1 (0.0065 absorbance/μM). Optimal conditions and the selectivity of this enzyme toward formaldehyde are described.     

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.     

GeX2(X=F,Cl)与甲醛环加成反应机理的理论研究

The mechanisms of the cycloaddition reaction of singlet GeX2(X=F,Cl) with formaldehyde was studied employing the HF/6-311+G theory. The electron-correlation corrections have been further considered by the fourth-order Muller-Plesset perturbation theory (MP4SDTQ/6-311+G). The results show that this reaction proceeds in two steps: ① Difluorogemylene and formaldehyde form an intermediate complex, which is a barrierless exothermal reaction; ② the intermediate complex isomerizes to form the product, which is a rate-control step in the whole reaction. In the second step, the calculated barrier heights are 216.7 and 196.4 kJ/mol before and after considering electron-correlation effects. Compared with that of the cycloaddition reaction of difluorosilylene with formaldehyde, the cycloaddition reaction of difluorogemylene with formaldehyde is relatively slow, whereas the cycloaddition reaction of dichlorogemylene with formaldehyde can be comparable in speed.     

The Electro‐Oxidation of Formaldehyde at a Boron‐Doped Diamond Electrode

Abstract

The characteristics of the boron‐doped diamond (BDD) electrode in this work were studied by atomic force microscope (AFM), scanning electron microscopy, and Raman spectroscopy. The electro‐oxidation of formaldehyde at the BDD electrode in 0.5 M K₂SO₄ with different pH was studied by cyclic voltammetry and amperometry. There is no significant oxidation peak of formaldehyde in acidic solution because the oxidation of formaldehyde is at the potential range of water discharge. However, in neutral solution, there is a well‐defined oxidation peak at about +2.2 V vs. Ag/AgCl. The relation between the response current and formaldehyde concentration is linear behavior at the concentration range from 50 to 600 µM. Besides, in neutral solution, the oxidation of formaldehyde is dominated by indirect oxidation at lower formaldehyde concentration, and it is dominated by direct oxidation at higher concentration. Finally, in alkaline solution, the oxidation of formaldehyde is dominated by indirect oxidation caused by a powerful oxidant and is related to the ratio of the amounts of formaldehyde and OH molecules at the BDD electrode surface.     

The analysis of combustion products : The estimation of traces of methanol in the presence of formaldehyde

In the analysis of combustion products, the estimation of traces of methanol can be rendered difficult by the presence of excess formaldehyde. A method is described for separating the formaldehyde from methanol by treating the solution with sodium bisulphite, and then carrying out a Chromatographie separation on filter paper. Ether carries the methanol to the end of the strip, leaving behind formaldehyde and hydrogen peroxide. The paper is cut into pieces, which are separately extracted with water, and the solution oxidised. The formaldehyde so formed ib estimated in the usual way with chromotropic acid.     

Assembled Organoruthenium(II) for Formaldehyde Decomposition and Hydrogen Production

Formaldehyde decomposition is not only an attractive method for hydrogen production, but also a potential approach for gaseous formaldehyde removal. In this research, we prepare some assembled organoruthenium through coordination reaction between Ru(p-Cymene)Cl₂ and bridge-linking ligands. It is a creative approach for Ru(p-Cymene)Cl₂ conversion into heterogeneous particles. The rigidity of bridge-linking ligand enables assembled organoruthenium to have highly ordered crystalline structure, even show clear crystal lattice with spacing of 0.19 nm. XPS shows the N−Ru bond are formed between bridge-linking ligand and Ru(p-Cymene)Cl₂. The assembled organoruthenium has high abundant active sites for formaldehyde decomposition at low temperature. The reaction rate could increase linearly with temperature and formaldehyde concentration, with a TOF of 2420 h⁻¹ at 90 °C. It is promising for gaseous formaldehyde decomposition in wet air or nitrogen. Formaldehyde conversion is up to 95 % over Ru-DAPM is 4,4′-diaminodiphenylmethane at 90 °C in air. Gaseous formaldehyde decomposition is a two-steps process under oxygen-free condition. Firstly, formaldehyde dissolve in water, and be converted into hydrogen and formic acid through formaldehyde-water shift reaction. Then intermediate formic acid will further decompose into hydrogen and carbon dioxide. We also find formaldehyde decomposition is a synergetic catalysis process of oxygen and water in moist air. Oxygen is conducive to formic acid desorption and decomposition on the active sites, so assembled organoruthenium exhibit slightly higher conversion for formaldehyde decomposition in moist air. This work proposes a distinctive method for gaseous formaldehyde decomposition in the air, which is entirely different from formaldehyde photocatalysis or thermocatalysis oxidation.     

Titrimetrische Bestimmung von Zink mit Äthylendiamintetraessigsäure in Gegenwart von Palladium(II)

Zusammenfassung Komplexometrische Methoden zur Bestimmung von Zink in Gegenwart von Palladium(II) wurden ausgearbeitet. Dabei wird Palladium(II) mit Kaliumcyanid getarnt und der Zinkgehalt entweder bei p_H 5,8 oder nach Demaskierung mit Chloralhydrat bei p_H 10 mit ÄDTA gegen Methylthymolblau titriert. Diese Zinkbestimmung läßt sich auch in Anwesenheit einer Mischung von Palladium(II), Kupfer(II), Nickel und Kobalt(II) durchführen.

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Summary Complexometric methods have been developed for determining zinc in the presence of palladium(II). In these procedures, Pa(II) is masked with potassium cyanide and the zinc content is titrated either at p_H 5.8 or after demasking with chloralhydrate is titrated with EDTA at p_H 10 in the presence of methylthymol blue. This zinc determination may also be conducted in the presence of a mixture of palladium(II), copper(II), nickel(II),and cobalt(II).

     

基于银纳米粒子的生成测定痕量甲醛

在碱性溶液中甲醛能还原Ag~+得到黄色银纳米粒子,使体系的共振光散射(RLS)强度增强,从而建立起测量环境中痕量甲醛的RLS新方法. 结果表明,新建方法测定甲醛的浓度线性范围为1.0×10~(-6)～2.0×10~(-5) mol/L,检出限为1.0×10~(-7) mol/L,样品加标测定的回收率为96.26%～103.32%. 并且不同浓度的甲醛还原Ag~+得到黄色银纳米粒子的颜色明显不同,基于此建立了一种可视化半定量测定痕量甲醛的新方法,此方法简便快速、灵敏度高. 用于环境水样、室内空气中甲醛的测定,结果满意.     

可视化测定痕量甲醛的研究

摘 要：共振光散射(RLS)法是近年发展起来的新的分析测试技术,它具有简便快速,灵敏度高的特点,已用于痕量元素或物质的分析。本文基于一定条件下,在碱性溶液中甲醛能还原Ag+ 得到黄色银胶,使体系的RLS增强,从而建立起测量环境中痕量甲醛的RLS新方法。结果表明,新建方法测定甲醛的浓度线性范围为1.0?10-6?2.0?10-5 mol/L,检出限为1.0?10-7 mol/L,样品加标测定的回收率为96.26%? 103.32%。并且不同浓度的甲醛还原Ag+ 得到黄色银纳米粒子的颜色明显不同,基于此建立了一种可视化半定量测定痕量甲醛的新方法,新建方法简便快速,灵敏度高。用于环境水样、室内空气中甲醛的测定,结果满意。     

Simultaneous determination of formaldehyde and methanol by flow-injection catalytic spectrophotometry

A flow-injection method is proposed for the simultaneous catalytic determination of formaldehyde and methanol on the basis of the catalytic action of formaldehyde upon the redox reaction between crystal violet and potassium bromate in a phosphoric acid medium and on-line oxidization of methanol into formaldehyde using a lead dioxide solid-phase reactor. The indicator reaction is monitored spectrophotometrically by measuring the decrease in the absorbance of crystal violet at the maximum absorption wavelength of 610 nm. A technique based on three sampling loops with a single injection valve is developed. The flow-injection system produces a signal of main peak with two shoulders of the same height. The height of the shoulders corresponds to the formaldehyde concentration, and the height difference between the shoulders and the main peak corresponds to the methanol concentration. The detection limit is 0.1 μg/mL for formaldehyde and 1.0 μg/mL for methanol with the sampling rate of 10 samples per hour. The relative standard deviations for 11 replicate determinations of formaldehyde (1.0 μg/mL) and methanol (10 μg/mL) are 1.1 and 2.1%, respectively. The method has been successfully applied to the simultaneous determination of formaldehyde and methanol in some gas samples. The text was submitted by the authors in English.     

Kinetic determination of formaldehyde and hexamethylenetetramine with a cyanide-selective electrode

An automatic potentiometric reaction-rate method is described for the determination of formaldehyde and hexamethylenetetramine. The formaldehyde reacts with cyanide, and the reaction rate is followed with a cyanide-selective electrode. The time required for the reaction to consume a fixed amount of cyanide, and therefore for the potential to increase by a preselected amount (8.0 mV), is measured automatically and related directly to the formaldehyde concentration. The average error for the determination of 60–300 μg of formaldehyde in a sample volume of 1.00 ml was about 1.3%. Amounts of hexamethyl-enetetramine in the range 50–250 μg in a sample volume of 0–050 ml were determined after acid hydrolysis to formaldehyde with an average error of about 1.6%. Measurement times were in the range 18–80 s for both determinations. The method has been applied to the determination of hexamethylenetetramine in pharmaceutical preparations.     

甲醛催化制氢的研究进展

氢有较高的能量密度,其能量转换过程可循环、零污染,是未来替代传统化石燃料的理想能源载体.甲醛相较于其它的氢载体,具有可规模制备、来源广泛、安全性高、易于输运、储存和转化的特点,已逐渐成为一种新的制氢原料.此外甲醛制氢技术还可以应用于其它对环境有一定毒性的有机化合物转变为清洁的氢的过程.我们较全面的总结了甲醛的工业化制备、催化转化制氢和催化剂的研究发展历程,详细介绍了近年来在相关领域的研究成果,分析对比了各种甲醛催化制氢技术的特点,并对未来甲醛制氢的发展前景进行了展望.