微波等离子体光谱技术的发展(二)

微波等离子体光源是一类重要的有较强激发能力的原子发射光谱光源,主要包括微波感生等离子体光源,电容耦合微波等离子体光源及微波等离子体炬光源。本文是微波等离子体光谱技术发展的第二部分,主要介绍了电容耦合微波等离子体光源及微波等离子体炬光源的结构原理和性能。并对它们的技术特点和进展进行评述。     

Synthesis and Transformations of Heterocyclic Compounds under the Influence of Microwave Radiation. (Review)

Published data on the synthesis and transformations of heterocyclic compounds with microwave treatment are analyzed and classified according to the types of products formed. The results of analogous reactions conducted with normal heating are given for comparison. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1123–1134, August, 2005.     

能源与环境应用中的微波催化研究进展

微波是一种能量传递方式。与传统电加热相比,微波加热具有加热速度快、热惯性小、选择性加热等特点,因而被视为一种优质的能量来源。微波催化是一种使用微波对反应系统供能,从而推动催化反应进行的化学过程。近年来,许多研究者致力于探索和发展微波催化技术,包括利用微波技术提升化学反应速率、开发具有出色微波吸收能力的催化剂、建立节能环保的微波催化系统等。本文首先介绍了微波的相关理论,讲述了材料对微波的吸收原理;然后从微波催化降解挥发性有机物（Volatile Organic Compounds, VOCs）、微波催化污水处理、微波催化生物质热解和微波催化碳氢化合物转化等方面综述了微波催化在能源环境中的应用;最后对微波催化过程的机理展开了讨论。     

微波等离子体光谱技术的发展(一)

微波等离子体光源是一类有较强激发能力的原子发射光谱光源,主要包括微波感生等离子体光源(MIP),微波电容耦合等离子体光源及微波等离子体炬光源。文章分两部分,第一部分介绍了微波感生等离子体光源的结构原理和性能,并对它们的技术特点和进展进行评述。低功率微波感生等离子体光源用于直接测定溶液中某些痕量金属元素是比较困难的,如Pb,Hg,Se等元素,但它已成功地与气相色谱联用用于测定C,H,O,N,S等难激发的非金属元素。高功率磁场激发的氮-微波感生等离子体光源(N2-MIP),允许使用通用玻璃同心雾化器产生湿试液气溶胶直接进入等离子体核心,等离子体能稳定运行,其分析性能近似于商用ICP光源,且运行费用低廉,是有发展前景的一种新型原子发射光谱光源。     

Microwave-Assisted Synthesis of Disulfides

Abstract

A new microwave-assisted synthesis methodology for the preparation of substituted disulfide derivatives is presented. 4-Substituted sulfenimides were reacted with 4-substituted thiols under neat (to right doughy consistency) conditions in chloroform, with both microwave heating and conventional methods. The resulting 4-substituted disulfide derivatives were obtained at higher yields and in shorter reaction times with microwave heating. Their chemistry was confirmed by ¹H-NMR, ¹³C-NMR, infrared (IR), and elemental analysis.

GRAPHICAL ABSTRACT     

微波有机合成反应的新进展

综述了近来微波辐射技术在有机合成应用中的新进展。着重介绍了微波有机合 成反应技术及其在重要有机合成反应中的应用。     

有机微波化学研究进展

本文综述了近几年来微波技术在有机合成方面的研究和应用进展。初步探讨了微波催化有机反应的作用机理, 并展望了有机微波化学的发展前景。     

微波对酶催化反应的影响及其微波效应的研究进展

综述了近年来微波对酶催化反应的影响,包括对酶催化反应速度与转化率或产率的影响,对酶促反应选择性与专一性的影响,对酶结构和活性的影响.总结了研究微波效应的几种技术方法及其在酶催化反应中的应用情况.     

一种通用的微波化学合成实验装置

自1986年以来,微波加热应用于化学领域已获得重要进展,与传统加热方法相比,微波加热有许多特点.首先,微波加热是内源性热源,是就地产热方式,与传统上热源均在反应物外 ,热量依靠传导、对流或辐射逐步由表及里传入反应物内部根本不同.微波加热的第二个特点是具有选择性,对各种非极性介质(如多种高分子材料,各种气体)微波很难对它们加热. 因而用这些材料制成的容器,对微波是"透明的",基本不发热,只是容器内的反应物才受微波作用而发热.     

Mcrowave-Assisted Rapid Solid-State Chemistry of Phosphate Materials

Abstract

The present work reports some applications of microwave processing in the synthesis of inorganic condensed phosphates.     

High-pressure microwave dissolution of ceramics prior to trace metal determinations by microwave induced plasma atomic emission spectrometry

A commercial laboratory microwave acid digestion system was evaluated for the acid dissolution of ceramic powders (Al₂O₃, AlN, BN and Si₃N₄) prior to the determination of their trace element content by microwave induced plasma atomic emission spectrometry. Newly designed vessels, capable of withstanding internal pressures of over 110 bar, provide rapid and satisfactory results for sample dissolution. Sample preparation time was approximately 30 min (including the subsequent cooling time and preparation of the final solution). Results from conventional stainless-steel acid digestion vessel (Teflon bomb) dissolution are compared with the microwave bomb results of microwave plasma atomic emission spectrometry.     

Changing Perspectives on the Strategic Use of Microwave Heating in Organic Synthesis

This Personal Account describes collaborative investigations into apocryphal microwave effects in organic chemistry. Focused research on microwave‐assisted organic synthesis has been fraught with confusion, controversy, and misinformation. Microwave heating is an undoubtedly useful tactic for organic synthesis, but whether or not it can offer strategic advantages remains an open question in the minds of many people. (Ironically, those who do not consider it an open question are split as to whether it has been resolved affirmatively or negatively.) Our research in this area is guided by the hypothesis that microwave heating can alter reaction kinetics in ways distinct from what is observable under conventional heating. Here we provide a succinct record of the origins of our interests, our initial queries and associated controversies, and recent efforts to identify, quantify, and begin to leverage selective microwave heating for strategic advantage in organic synthesis.     

Recent Progress in Iron-Based Microwave Absorbing Composites: A Review and Prospective

With the rapid development of communication technology in civil and military fields, the problem of electromagnetic radiation pollution caused by the electromagnetic wave becomes particularly prominent and brings great harm. It is urgent to explore efficient electromagnetic wave absorption materials to solve the problem of electromagnetic radiation pollution. Therefore, various absorbing materials have developed rapidly. Among them, iron (Fe) magnetic absorbent particle material with superior magnetic properties, high Snoek’s cut-off frequency, saturation magnetization and Curie temperature, which shows excellent electromagnetic wave loss ability, are kinds of promising absorbing material. However, ferromagnetic particles have the disadvantages of poor impedance matching, easy oxidation, high density, and strong skin effect. In general, the two strategies of morphological structure design and multi-component material composite are utilized to improve the microwave absorption performance of Fe-based magnetic absorbent. Therefore, Fe-based microwave absorbing materials have been widely studied in microwave absorption. In this review, through the summary of the reports on Fe-based electromagnetic absorbing materials in recent years, the research progress of Fe-based absorbing materials is reviewed, and the preparation methods, absorbing properties and absorbing mechanisms of iron-based absorbing materials are discussed in detail from the aspects of different morphologies of Fe and Fe-based composite absorbers. Meanwhile, the future development direction of Fe-based absorbing materials is also prospected, providing a reference for the research and development of efficient electromagnetic wave absorbing materials with strong absorption performance, frequency bandwidth, light weight and thin thickness.     

微波-超声复合场辅助水介质砜类化合物合成

发展了一种微波-超声复合场下绿色高效合成砜类化合物的简便方法。 以芳甲基氯和苯亚磺酸钠为原料,以水为反应介质,在微波-超声复合场辅助下合成了一系列芳甲基苯基砜。 通过考察微波功率、超声功率、原料投料比、溶剂体积和反应时间等因素的影响,得出了苄基氯与苯亚磺酸钠之间模型反应的最优反应条件:微波功率为40 W,超声功率为50 W,苄基氯与苯亚磺酸钠的摩尔配比为1:3,反应时间为5 min。 在此条件下合成的苄基苯基砜产率为83%。 相比常规油浴条件,在微波-超声复合场的强化下反应速率提升了约42倍。 该方法具有较好的底物适应性,成功合成了23种砜类化合物。     

微波辐射破乳研究进展

综述了微波辐射破乳的有关研究进展。微波辐射是一种有效的破乳手段，与重力沉降、化学、加热等破乳方法相比，能显著地加速稠油体系，含天然表面活性物质、无机盐、固体粒子、三元复合驱剂等乳状液的破乳，提高破乳效果，并且能够提高破乳脱出水的透光率。无机盐与微波辐射两种破乳方式存在加和作用，在极少量的NaCl，MgCl2，caCl2，KCl存在时，用微波辐射120～150s，破乳率可达100％。微波辐射破乳作为一种很有吸引力的破乳方法已在实验室和油田现场取得成功。     

Rapid Microwave‐Promoted Synthesis of Polyurethanes from a Fluorene Unit‐Containing Diol and Diisocyanates

A fluorene diol derivative, 9,9‐bis[4‐(2‐hydroxyethoxy)phenyl]fluorene ( 1 ), reacted with diisocyanates such as 1,3‐bis(isocyanatomethyl)cyclohexane ( 2a ), 1,6‐diisocyanatohexane ( 2b ), and 1,3‐bis(isocyanatomethyl)benzene ( 2c ) under temperature‐controlled microwave irradiation to form the corresponding polyurethanes with being 30 000 to 60 000, measured by GPC with reference to polystyrene standards within 5 to 10 min at 160 to 200 °C. In the reactions of 2a and b , the molecular weights were 15 to 20 times higher than those obtained by conventional oil bath heating. For a solvent of the microwave‐promoted reaction, a hydrocarbon compound, decalin, is preferably used to undergo the polymerization cleanly without unfavorable coloration and/or gelation.

     

One-pot synthesis of N-substituted pantolactams from pantolactone

Rac-N-substituted pantolactams (5) are readily obtained in medium to good yields by reaction of rac-pantolactone (1) with primary amines under acid catalysis, whether at 250°C in a pressure reactor or under microwave irradiation. It appears that the amine can react with pantolactone at the carbonyl carbon atom to give a hydroxyamide (3) in a reversible way and at the methylene carbon atom to give a γ-amino acid (4). The last one on dehydration would give the corresponding pantolactam (5).     

Practical and Scalable Organic Reactions with Flow Microwave Apparatus

Microwave irradiation has been used for accelerating organic reactions as a heating method and has been proven to be useful in laboratory scale organic synthesis. The major drawback of microwave chemistry is the difficulty in scaling up, mainly because of the low penetration depth of microwaves. The combination of microwave chemistry and flow chemistry is considered to overcome the problem in scaling up of microwave‐assisted organic reactions, and some flow microwave systems have been developed in both academic and industrial communities. In this context, we have demonstrated the scale‐up of fundamental organic reactions using a novel flow microwave system developed by the academic‐industrial alliance between the University of Shizuoka, Advanced Industrial Science and Technology, and SAIDA FDS. In this Personal Account, we summarize the recent progress of our scalable microwave‐assisted continuous synthesis using the SAIDA flow microwave apparatus.     

Microwave-assisted synthesis of corroles

The recently developed Gross's method for the synthesis of corroles has been modified and successfully applied to the preparation of new free base tris-aryl- and tris-pyrimidyl-corroles using solvent-free conditions and microwave irradiation. Compared to conventional heating, the microwave technique afforded an increase in corrole yields of ca. 30% and led to noticeably cleaner reaction mixtures. It is demonstrated that short reaction times and high temperatures are required to afford optimum yields.     

The Microwave-Assisted Dehydrative Cyclization of Thiosemicarbazides Forming Substituted 1,2,4-Triazoles

Different types of 4,5-disubstituted 1,2,4-triazole-3-thiones were prepared by microwave irradiation as well as by a classical method. The beneficial effect of microwave irradiation on the dehydrative cyclization of thiosemicarbazides in different reaction media is described. Our results show that the effect of microwave irradiation on the reaction studied was the shortening of reaction times (from 2–9 h to 2–4 min) and a minor decrease (1–4%) in yields. The structure of the new compounds was established by FTIR, MS, and ¹H NMR spectral data.