Photoinduced Decomposition of Formaldehyde on Rutile TiO2(100)-(1×1)?

We have investigated the photoinduced decomposition of formaldehyde (CH₂O) on a rutile TiO₂(100)-(1×1) surface at 355 nm using temperature-programmed desorption. Products, formate (HCOO^-), methyl radical (CH₃·), ethylene (C₂H₄), and methanol (CH₃OH) have been detected. The initial step in the decomposition of CH₂O on the rutile TiO₂(100)-(1×1) surface is the formation of a dioxymethylene intermediate in which the carbonyl O atom of CH₂O is bound to a Ti atom at the five-fold-coordinated Ti⁴⁺ (Ti_5c) site and its carbonyl C atom bound to a nearby bridge-bonded oxygen (O_b) atom, respectively. During 355 nm irradiation, the dioxymethylene intermediate can transfer an H atom to the O_b atom, thus forming HCOO^- directly, which is considered as the main reaction channel. In addition, the dioxymethylene intermediate can also transfer methylene to the O_b row and break the C-O bond, thus leaving the original carbonyl O atom at the Ti_5c site. After the transfer of methylene, several pathways to products are available. Thus, we have found that O_b atoms are intimately involved in the photoinduced decomposition of CH₂O on the rutile TiO₂(100)-(1×1) surface.     

草酸盐对甲醛光催化氧化降解过程促进作用的研究

采用漫反射红外光谱（DRIFTS）技术和循环伏安法对TiO2光催化剂上甲醛光催化氧化过程中催化剂表面吸附、降解行为进行了考察．研究了草酸盐对甲醛光催化氧化降解行为的影响,结果表明低浓度草酸钠的加入提高了甲醛的降解效率,这个结果归因于草酸根离子的存在能够清除吸附位上积聚的甲酸及类似中间产物．光电化学实验进一步证实了草酸钠对甲醛光催化氧化中间产物的清除作用．     

乙酰乙酸乙酯分光光度法测定甲醛的研究

乙酰乙酸乙酯在弱酸性溶液中与甲醛及铵离子反应,生成2,6-二甲基-1,4-二氢-3,5-吡啶二乙酸乙酯,该化合物在375nm处有最大吸收,以甲醛计的摩尔吸光系数为5.533×103mol·cm-1·L-1;利用该反应建立了测定食品中微量甲醛的新方法,甲醛质量浓度在0.08～4.0mg/L成线性关系。并用质谱分析了产物,证实在水溶液中该反应遵循汉秋希吡啶合成法的原理。     

溴甲酚绿动力学光度法测定甲醛

在磷酸介质中 ,甲醛对溴酸钾氧化溴甲酚绿有催化作用 ,建立了测定微量甲醛的催化动力学光度法。在适宜实验条件下 ,方法的线性范围为 1— 15 mg/L;检出限为 0 .4 1mg/L。用于检测废水中甲醛含量 ,结果满意。     

l-Threonine-catalysed asymmetric α-hydroxymethylation of cyclohexanone: application to the synthesis of pharmaceutical compounds and natural products

l-Threonine has been found to be an efficient catalyst for the asymmetric α-hydroxymethylation of cyclohexanone with formalin. Reducing the amount of water in the reaction by the addition of magnesium sulfate as a dehydrating additive significantly improves the yield. Applications of (S)-2-hydroxymethyl cyclohexanone and the chiral building blocks derived therefrom for the synthesis of pharmaceutical compounds and natural products have been explored.     

Formaldehyde around 3.5 and 5.7-μm: Measurement and calculation of broadening coefficients

Self- and N₂-broadening coefficients of H₂CO have been retrieved in both the 3.5 and 5.7-μm spectral regions. These coefficients have been measured in FT spectra for transitions with various J (from 0 to 25) and K values (from 0 to 10), showing a clear dependence with both rotational quantum numbers J and K. First, an empirical model is presented to reproduce the rotational dependence of the measured self- and N₂-broadening coefficients. Then, calculations of N₂-broadening of H₂CO were made for some for 3296 ν₂ transitions using the semi-classical Robert-Bonamy formalism. These calculations have been done for various temperatures in order to obtain the temperature dependence of the line widths. Finally, self- and N₂-broadening coefficients, as well as temperature dependence of the N₂-widths has been generated to complete the whole HITRAN 2008 version of formaldehyde (available as supplementary materials).     

The Stabilization of Small Concentrations of Formaldehyde in A queous Solutions

Abstract

Based on the Hantzsch-reaction, a stabilization (fixation) of small concentrations of formaldehyde in aqueous solutions (<0.4μg CH₂0/ml) can be performed, allowing a storage of these solutions for 1 week at room temperature, in darkness. Using the fluorescent nature of 3,5-diacetyl-1,4-dihydrolutidine (λ_ex = 410 nm, λ_em = 510 nm), formed as a result of the Hantzsch-reaction, CH₂0-concentrations down to 0.02 μ/ml can be determined fluorimetrically up to 7 days after preparation (sampling).     

甲醛与甲酰胺相互作用的从头算研究

在MP2 /6 3 1G(d)和MP2 (FC) /6 3 11+ +G(d ,p)水平上 ,对H2 CO和HCONH2 以及设计的 3种构型H2 CO…HCONH2 复合物等进行几何全优化计算 ,经振动频率分析 ,确认它们为势能超曲面上的稳定驻点 .然后在MP2 /6 3 11+ +G(2df,3p)水平上进行单点能计算和基组重叠误差 (BSSE)校正以获得相互作用能 .并利用自然键轨道理论和分子中的原子理论探讨H2 CO和HCONH2 相互作用的本质 .分子间相互作用的能量分解分析显示 ,静电能在H2 CO…HCONH2 相互作用能中占主导地位