Reaction of the carbonate radical with substituted anilines

Rate constants for the reaction of carbonate radical with aniline and some parasubstituted anilines have been determined by the flash photolysis technique. Using σ⁺ para values the rate constants at pH 8.5 correlate very well with the Hammett equation yielding ρ= − 1. The carbonate radical oxidises aniline giving the anilino radical. The products so formed have been identified through studies under conditions of continuous irradiation.     

2,5‐Dihydro‐1H‐imidazole‐Based Nitroxides as Prospective Mediators in Living Radical Polymerization

A number of spectroscopic methods were applied to obtain kinetic parameters of reactions modelling the 2,5‐dihydro‐1H‐imidazole 1‐oxide mediated living polymerization of acrylates. The homolysis rate constants of alkoxyamines based on five nitroxides were measured by EPR spectroscopy at different temperatures. The recombination rate constants k_c between the corresponding alkyl radicals and the nitroxides were measured by means of laser flash photolysis. The time‐resolved chemically induced dynamic nuclear polarization (TR‐CIDNP) experiments revealed the negligible contribution of disproportionation in the recombination reaction. In addition, the thermodecomposition of alkoxyamines in the NMR probe showed the absence of intramolecular elimination of hydroxylamines from the corresponding alkoxyamines. Analysis of the kinetic parameters showed that the 2,5‐dihydro‐1H‐imidazole 1‐oxide type radicals are promising mediators for the living polymerization of acrylates and methacrylates.     

CCl4的光解微观机制研究

利用激光光解瞬态吸收光谱技术,研究有氧和无氧条件下CCl4的激光光解.结果表明,在248 nm激光作用下, CCl4发生了单光子吸收,反应生成{CCl4－Cl}σ电荷转移复合物、(CCl3＋…Cl－)离子对、CCl3O2过氧自由基等瞬态物种,它们的衰减过程是表观一级反应. {CCl4－Cl}σ电荷转移复合物在有氧/无氧条件下的拟合衰减速率常数分别是3.38×106 s－1和3.65×106 s－1,它的形成不受氧气含量影响. (CCl3＋…Cl－)离子对在有氧/无氧条件下的拟合衰减速率分别为3.73×107 s－1和3.02×107 s－1,它的形成也不受氧气含量影响, CCl3O2过氧自由基需在有氧条件下形成,拟合衰减速率是2.32×104 s－1.     

Reactivity of the M-(η-alkyne) bond [M = Cr, W]: A kinetic and DFT study

The displacement of η²-coordinated 1-hexyne and 3-hexyne by 2-picoline from the Cr(CO)₅, BzCr(CO)₂ and W(CO)₅ fragments was studied. For the Cr systems, the data is consistent with a dissociative mechanism of alkyne displacement from the metal center. For W(CO)₅(η²-1-hexyne), the alkyne displacement follows a largely associative mechanism. The bond dissociation enthalpies obtained from the kinetic analysis are in good agreement with the values obtained by detailed DFT calculations. The calculations indicate that the energy required for the steric reorganization of the alkyne ligand prior to binding with the metal is an important factor in the determination of the overall metal-(η²-alkyne) bond strength.     

Oxidative Catalysis by TAMLs: Obtaining Rate Constants for Non-Absorbing Targets by UV-Vis Spectroscopy

Understanding the catalysis of oxidative reactions by TAML activators of peroxides, i. e. iron(III) complexes of tetraamide macrocyclic ligands, advocated a spectrophotometric procedure for quantifying the catalytic activity of TAMLs for colorless targets (k_II′, M⁻¹ s⁻¹), which is incomparably more advantageous in terms of time, cost, energy, and ecology than NMR, HPLC, UPLC, GC-MS and other similar techniques. Dyes Orange II or Safranin O (S) are catalytically bleached by non-excessive amount of H₂O₂ in the presence of colorless substrates (S₁) according to the rate law: −d[S]/dt=k_Ik_II[H₂O₂][S][TAML]/(k_I[H₂O₂]+k_II[S]+k_II′[S₁]). The bleaching rate is thus a descending hyperbolic function of S₁ : v=ab/(b+[S₁]). Values of k_II′ found from a and b for phenol and propranolol with commonly used TAML [Fe^III{o,o′-C₆H₄(NCONMe₂CO)₂CMe₂}₂(OH₂)]⁺ are consistent with those for S₁ (phenol, propranolol) obtained directly by UPLC. The study sends vital messages to enzymologists and environmentalists.     

Theoretical study on the gas phase reaction of propargyl alcohol with hydroxyl radical

The reaction of propargyl alcohol with hydroxyl radical has been studied extensively at CCSD(T)/aug‐cc‐pVTZ//MP2/cc‐pVTZ level. This is the first time to gain a conclusive insight into the reaction mechanism and kinetics for this important reaction in detail. Two reaction mechanisms were revealed, namely addition/elimination and hydrogen abstraction mechanism. The reaction mechanism confirms that OH addition to C?C triple bond forms the chemically activated adducts, IM1 (·CHCOHCH₂OH) and IM2 (CHOH·CCH₂OH), and the hydrogen abstraction pathways (? CH₂OH bonded to the carbon atom and alcohol hydrogen) may occur via low barriers. Harmonic model of Rice–Ramsperger–Kassel–Marcus theory and variational transition state theory are used to calculate the overall and individual rate constants over a wide range of temperatures and pressures. The calculated rate constants are in good agreement with the experimental data. At atmospheric pressure with Ar as bath gas, IM1 (·CHCOHCH₂OH) and IM2 (CHOH·CCH₂OH) formed by collisional stabilization are dominant in the low temperature range. The production of CHCCHOH + H₂O via hydrogen abstraction becomes dominate at higher temperature. The fraction of IM3 (CH₂COHCH₂·O) is very significant over the moderate temperature range. © 2014 Wiley Periodicals, Inc.     

卤代有机污染物的光化学降解

包括全氟或部分氟代化合物（PFCs）、氯代有机物（COCs）以及溴代有机物（BOCs）等的卤代有机污染物（halogenated organic contaminants,HOCs）排放到环境中会表现出持久性有机污染物的特征,因此涉及HOCs性质、光吸收与量子效应、材料与界面特性、环境条件等方面优化的光化学清除方法成为一个重要的研究方向。基于此,本文归纳分析了光激发催化剂产生活性物种如h_VB⁺、e_CB^-、 ·OH、e_aq^-等氧化或还原全氟辛酸、多氯联苯、多溴联苯醚的反应机理及直接光解机理,指出HOCs的光化学降解主要是通过其与活性物种之间电子转移或其激发态光致还原脱卤来实现,认为光催化材料和反应过程优化设计是影响光催化降解HOCs的重要因素。基于目前已经取得的研究发现与成果,从界面电子转移、材料能带信息、反应与分离集成化等方面提出本领域未来学术与技术层面值得深入探索的关键问题。     

UVphotolysis of the binary mixtures of VOCs in dry nitrogen stream

Summary The effect of H/Cl atomic ratio on the relative contribution of direct photolysis and reactions based on •Cl radical to the photodecomposition of chlorinated methanes was investigated in their binary mixtures.</o:p>