Reaction kinetics and thermochemistry of the chemically activated and stabilized primary ethyl radical of methyl ethyl sulfide,CH3SCH2CH2•, with O2 to CH3SCH2CH2OO•

Oxidation of methyl ethyl sulfide (CH₃SCH₂CH₃, methylthioethane, MES) under atmospheric and combustion conditions is initiated by hydroxyl radicals, MES radicals, generated after loss of a H atom via OH abstraction, will further react with O₂ to form chemically activated and stabilized peroxyl radical adducts. The kinetics of the chemically activated reaction between the CH₃SCH₂CH₂• radical and molecular oxygen are analyzed using quantum Rice-Ramsperger-Kassel theory for k(E) with master equation analysis and a modified strong-collision approach to account for further reactions and collisional deactivation. Thermodynamic properties of reactants, products, and transition states are determined by the B3LYP/6-31+G(2d,p), M062X/6-311+G(2d,p), ωB97XD/6-311+G(2d,p) density functional theory, and CBS-QB3, G3MP2B3, and G4 composite methods. The reaction of CH₃SCH₂CH₂• with O₂ forms an energized peroxy adduct CH₃SCH₂CH₂OO• with a calculated well depth of 34.1 kcal mol⁻¹ at the CBS-QB3 level of theory. Thermochemical properties of reactants, transition states, and products obtained under CBS-QB3 level are used for calculation of kinetic parameters. Reaction enthalpies are compared between the methods. The temperature and pressure-dependent rate coefficients for both the chemically activated reactions of the energized adduct and the thermally activated reactions of the stabilized adducts are presented. Stabilization and isomerization of the CH₃SCH₂CH₂OO• adduct are important under high pressure and low temperature. At higher temperatures and atmospheric pressure, the chemically activated peroxy adduct reacts to new products before stabilization. Addition of the peroxyl oxygen radical to the sulfur atom followed by sulfur-oxygen double bond formation and elimination of the methyl radical to form S(= O)CCO• + CH₃ (branching) is a potentially important new pathway for other alkyl-sulfide peroxy radical systems under thermal or combustion conditions.     

手性炔丙醇的不对称催化合成研究进展

手性炔丙醇是一种重要中间体化合物,作为合成多种光学活性化合物的重要合成前体受到学者们广泛关注。目前通过酮的不对称催化反应合成手性炔丙醇的研究开发具有极大发展前景,因此本文围绕酮类化合物的不对称催化反应来进行综述,结合相关反应最新研究进展,全面总结并分类了不对称催化还原、催化不对称加成等反应类型,介绍了合成不同结构手性炔丙醇的新思路,并对酮的不对称催化反应在未来能成为工业化重要生产途径作出展望。     

缩醛/缩酮的合成研究进展

醛/酮与醇或原甲酸酯进行亲核加成反应生成的产物缩醛/缩酮,是一类重要的有机化合物。在有机合成中,该反应也广泛用于醛/酮羰基的保护或者乙二醇的保护,因此,缩醛/缩酮的合成研究引起广泛的关注。本文根据反应体系的不同,从酸催化、电催化和光催化三个方面对近年来缩醛/缩酮的合成研究进展进行详细综述。期望该综述作为学生基础有机化学课程的课后拓展阅读内容,能加深学生对基础反应的理解,培养学生的科研创新思维。     

Visible light-driven acridone catalysis for atom transfer radical polymerization

Acridone as a new kind of visible light photocatalyst has been developed to catalyze metal free atom transfer radical polymerization (ATRP). The photocatalyst possess low excited state potential as can undergo an oxidative quenching pathway to initiate ATRP of vinyl monomers. Kinetic study and light on/off reaction demonstrate the “living”/controlled nature of the polymerization by light. Block copolymers can be achieved by using PMMA as macroinitiator to reinitiate polymerization of other vinyl monomers, which shows highly preserved Br chain-end functionality in the synthesized polymers. Moreover, the polymerization can be conducted under air atmosphere as most photocatalysts need anaerobic condition, which may give inspiration of further application of this kind of photocatalyst.     

Glass transition and miscibility in blends of two semicrystalline polymers: Poly(aryl ether ketone) and poly(ether ether ketone)

Binary melt‐blended mixtures of two aryl ether ketone polymers (i.e., a new poly(aryl ether ketone) (code name PK99) and poly(ether ether ketone) (PEEK), have been studied. Polymer miscibility in glassy amorphous (or melt) domains has been demonstrated for the binary blend comprising of two aryl‐ether‐ketone‐type semicrystalline polymers. Composition‐dependent, single T_g was observed within full composition range in the PK99/PEEK blends, and the narrow T_g breadth also suggests that the scale of mixing was fine and uniform. To better resolve any possible overlapping T_g's, physical aging was imposed on a comparison set of blend samples for the purpose of improving detectability of overlapped multiple transitions if existing. The result still showed one single T_g. The relative sharp T_g and lack of cloud point transition suggest that the scale of molecular intermixing is good. Phase homogeneity was further confirmed using optical and scanning electron microscopy. The X‐ray diffractograms suggest that isomorphism does not exist in the PK99/PEEK blends and that the crystal forms of the respective polymers remain distinct and unchanged by the miscibility in the amorphous region. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1485–1494, 1999     

纳米复合固体超强酸SO42-/CoFe2O4的制备和表征

采用纳米化学制备技术合成了新型的纳米复合团体超强酸催化剂ＳＯ４２－／ＣｏＦｅ２Ｏ４。用ＸＲＤ、ＴＥＭ、ＸＰＳ、红 外光谱和比表面测定等技术研究了该催化剂的结构形态,结果表明：所研制的ＳＯ４２－／ＣｏＦｅ２Ｏ４催化剂为晶态纳 米粒子（＜ ５０ｎｍ）,比表面积很大（１５７ｍ２· ｇ－１）,ＳＯ４２－与氧化物的金属离子呈无机双齿螯合状配位化合物的结 合形式。以乙酸乙酯合成为模型反应考察了该催化剂的催化活性,比较了酸性和酸强度,推断出该催化剂的酸 强度Ｈ０＜－１４．５。     

(Liquid + liquid) equilibria of (water + propionic acid + methyl isoamyl ketone or diisobutyl ketone or ethyl isoamyl keton) at T = 298.2 K

(Liquid + liquid) equilibrium (LLE) data for (water + propionic acid + solvent) were measured at T = 298.2 K and atmospheric pressure. The solvents were methyl isoamyl ketone (5-methyl-2-hexanone), ethyl isoamyl ketone (5-methyl-3-heptanone) and diisobutyl ketone. The tie-line data were correlated by means of the NRTL and UNIQUAC equation, and compared with results predicted by the UNIFAC method. A comparison of the extracting capabilities of the solvents was made with respect to distribution coefficients, separation factors, and solvent free selectivity bases.     

A novel vapor phase process for aromatic ketone synthesis

The vapor phase catalytic reaction between aromatic carboxylic acid and acetic acid was investigated. Many metal oxides catalyzed the reaction between 2methylbenzoic acid (OTA) and acetic acid (AA) to produce 2methylacetophenone (OMA), and weakly acidic oxides such as Th, U, Ce, and La oxide exhibited higher yield of OMA. The OMA yield depended on the catalyst support. SiO₂, Al₂O₃, TiO₂, and ZrO₂ with a surface area of less than 200 m² g^–1 appeared to be suitable as industrial catalyst supports. CeO₂ on Al₂O₃was chosen as an industrial catalyst for the synthesis of OMA because of higher productivity, longer catalyst life, and lifting of legal restrictions on catalyst handling. This catalyst system can also be applied to the syntheses of acetophenone, nitroacetophenone, and chloroacetophenone.     

含间苯基聚醚酮醚酮酮的合成和性能研究

自英国ＩＣＩ公司开发聚醚醚酮（ＰＥＥＫ）并于八十年代初期商品化以来［１］,聚芳醚酮作为一类新型结构的高性能特种工程塑料得到了惊人的发展,不同结构的聚芳醚酮相继出现．Ｊａｎｓｏｎ［２］等以对苯二甲酰氯（ＴＰＣ）和４,４′ 二苯氧基二苯酮（ＤＰＢＰ）为单...     

联苯聚醚醚酮酮的结晶动力学的研究

通过ｄｓｃ 方法对新型聚芳醚酮联苯聚醚醚酮酮（ＰＥＥＫＤＫ） 的等温及非等温熔融结晶动力学进行了研究,运用Ａｖｒａｍｉ 方程分析了其等温结晶行为,求得了等温结晶活化能,平衡熔点,成核参数,并与其它聚芳醚酮类聚合物进行了比较。同时,对ＰＥＥＫＤＫ的非等温结晶动力学也进行了研究。