Origin of the Correlation of the Rate Constant of Substrate Hydroxylation by Nonheme Iron(IV)–oxo Complexes with the Bond‐Dissociation Energy of the C?H Bond of the Substrate

A series of hydrogen‐abstraction barriers of a nonheme iron(IV)–oxo oxidant mimicking the active species of taurine/α‐ketoglutarate dioxygenase (TauD) are rationalized by using a valence‐bond curve‐crossing diagram (see figure). It is shown that the barriers correlate with the strength of the C? H bond. Furthermore, electronic differences explain the differences between nonheme and heme iron(IV)–oxo hydrogen‐abstraction barriers.

     

Homogeneous methylation of wood pulp cellulose dissolved in LiOH/urea/H2O

Spruce sulphite cellulose (number average degree of polymerization 620) dissolved in an aqueous solution of 8% (w/w) LiOH*H₂O and 12% (w/w) urea was methylated with dimethyl sulphate (DMS). By varying the reaction temperature between 22 and 50 °C, the molar ratio between 9 and 15 mol DMS per mol anhydroglucose unit, and the reaction time from 4 to 24 h, methyl cellulose (MC) with degree of substitution (DS) values in the range of 1.07 and 1.59 was prepared. The chemical structure of MC was analysed by FTIR and ¹H NMR spectroscopy. The turbidity (given in nephelometric turbidity units, NTU) of the aqueous solution of MC reached an optimum of 10 NTU for a product obtained with 12 mol DMS/mol AGU at 50 °C. GPC measurements revealed polymer degradation to a certain extent. The intrinsic viscosity and the Huggins constant k of the MC samples increased with increasing DS value. The MC samples possess k values higher than 0.8, indicating association of the polymer chain. The zero-shear viscosity decreased with increase of both temperature and the amount of methylation agent due to the depolymerization. During the heating/cooling cycle (20-90 °C) of the aqueous solutions of MC, it was observed that samples synthesized at 22 °C with DS values lower than 1.3 did not undergo phase separation in aqueous solution. Phase separation hysteresis with a precipitation temperature up to 80 °C was obtained for aqueous solutions of MC with DS values between 1.07 and 1.66 synthesized at higher temperatures. The functionalization pattern determined by GLC of the corresponding partially methylated glucitol acetates is close to randomness and comparable with those of commercial MC samples.     

One-pot synthesis of sulfonamides from methyl sulfinates using ultrasound

Room temperature ultrasonic irradiation of neat mixtures of methyl sulfinates and primary or secondary amines (1.5 equiv) produced sulfinamides, which on m-CPBA oxidation (in dichloromethane) were converted into the corresponding sulfonamides. The two steps can be accomplished in one pot, in good overall yields, when using secondary amines, but primary amines give better sulfonamide yields when the peracid oxidation is effected on the purified sulfinamide. This constitutes a mild, efficient, and potentially scalable route to sulfonamides, which obviates the use of water sensitive, often lachrymatory sulfonyl chlorides and large reagent excesses.     

Synthesis of 2-arylacrylic esters from aryl methyl ketones via Wittig reaction/singlet oxygen ene reaction

An efficient synthetic method has been developed for the synthesis of 2-arylacrylic esters from the corresponding aryl methyl ketones via Wittig reaction and singlet oxygen ene reaction. Wittig reaction to aryl methyl ketones with (methoxymethyl)triphenylphosphonium chloride in basic condition afforded the methyl enol ethers, and then 2-arylacrylic esters were obtained by singlet oxygen ene reaction, followed by tosylation and elimination in one-pot to the methyl enol ethers in good yields.     

Stereoselective synthesis of erythro-β-chloroamines and their conversion into functionalized trans-oxazolidin-2-ones

New erythro-β-chloroamines were synthesized by a mild and efficient stereoselective chlorination of unprotected amino alcohol diesters. These products are shown to be excellent building blocks for the synthesis of new substituted trans-oxazolidin-2-ones.     

甲基橙亚硝化极谱法测定亚硝酸根

研究了甲基橙亚硝化产物的极谱波行为 ,提出了亚硝化极谱法测定亚硝酸根的灵敏极谱波新体系。在 0 .6mol/L 盐酸中 ,甲基橙与 NO-2 的亚硝化反应产物在极谱仪上于 - 0 .31 V( vs.SCE)可获得灵敏的极谱波。导数波高与亚硝酸根浓度在 1 .0 9× 1 0 -7～ 1 .0 9× 1 0 -5mol/L范围内成正比 ,检出限为 6.52× 1 0 -8mol/L。研究了极谱波行为及反应机理。并利用该法测定了水样中的亚硝酸根     

Kinetics of the Reaction of Abstracting Hydrogen from Ethylene by Hydrogen Atom

Hydrogen abstraction reaction, H C2H4 --H2 C2H2 was studied by using A initio SCF method. Ge-ometries were fully optimized at SCF level and energies were computed at STO-3G basis set for reactants and transition state. Vibrational analysis was performed thereupon. Finally, the rate constant calculations were carried out at different temperatures for all range of reaction temperature according to Eyring's sbwlute reaction rate theory. The calculated activation energy is 12. 68 kcal/mol, lower than observed value (H. S kcal/mol) by 1. 82 kcal/mol only. The agreement of the calculated rate constants with the experiments is satisfactory.     

新引发体系引发MMA活性自由基聚合

近年来 ,关于活性自由基聚合的研究极为活跃 ,已经发现了多种基于增长链自由基被可逆钝化形成休眠种的活性自由基聚合方法[1,2 ] .它们主要包括引发转移终止剂 ( Iniferter) ,稳定自由基聚合( SFRP) ,原子转移自由基聚合 ( ATRP) ,可逆加成 -断链链转移聚合 ( RAFT)等 .其中 ATRP因其具有可聚合单体多 ,反应条件相对缓和等优点而成为该领域的研究热点 [3～ 5] .ATRP活性自由基聚合的实现主要是在过渡金属催化剂的作用下 ,通过循环往复的碳 -卤键的活化、加成、碳 -卤键的再形成而得到最终活性的聚合物 ,引发体系由引发剂、过渡金属…     

1-甲基-1-乙氧基-1-烷硫基甲烷类化合物的合成研究

本文以乙缩醛和烷基硫醇为原料,在30－35℃于四氯化碳中反应20min左右,分别合成1－甲基－1－乙氧基－1－烷硫基甲烷,经红外光谱,质谱以及核磁共振谱检测,确证了产物结构。     

Fe3O4@HTlc的制备及其对甲基橙的吸附研究

采用液相非稳态共沉淀法制备了磁性镁铝类水滑石(Fe3O4@HTlc),采用透射电子显微镜、粉末X射线衍射仪、傅里叶变换红外光谱仪、振动样品磁强计、比表面分析仪、微电泳仪等对样品的形貌和结构进行了表征,并比较了 Fe3O4@HTlc和HTlc对甲基橙的吸附性能。结果表明,Fe3O4@HTlc为顺磁性、具有核-壳结构和较大比表面积、带有正电荷的近球状颗粒。甲基橙在Fe3O4@HTlc和HTlc上的吸附动力学曲线均符合准一级动力学方程;吸附等温线均符合Langmuir吸附等温式;298 K时Fe3O4@HTlc和HTlc对甲基橙的饱和吸附量分别为138.89和147.06 mg/g,但Fe3O4@HTlc对甲基橙有较强吸附推动力和较短的吸附平衡时间。二者对甲基橙的吸附量均随温度的升高和pH (5~11)的增加而降低。