Free-radical carbon-carbon bond formation in organic synthesis

Organic chemists have begun to use intra- and intermolecular free-radical addition reactions to develop useful synthetic transformations. Carboncentered radicals can form bonds with electron-rich or electron-deficient alkenes, allenes, and acetylenes. Radical addition reactions can also be used to construct hindered carbon-carbon bonds. These characteristics, as well as the large number of functional groups that tolerate free-radical conditions contribute to the importance of such reactions in organic synthesis.     

A molecular shift register based on electron transfer

An electronic shift-register memory at the molecular level is described. The memory elements are based on a chain of electron-transfer molecules and the information is shifted by photoinduced electron-transfer reactions. This device integrates designed electronic molecules onto a very large scale integrated (silicon microelectronic) substrate, providing an example of a "molecular electronic device" that could actually be made. The design requirements for such a device and possible synthetic strategies are discussed. Devices along these lines should have lower energy usage and enhanced storage density.     

干旱胁迫下红麻叶片的差异蛋白表达分析

【目的】研究耐旱性高的红麻品种在干旱胁迫条件下的蛋白质表达,揭示红麻耐旱性的生理机制。【方法】以鉴定出的耐旱性红麻品种GA42为材料,在苗期（五叶期）设置正常供水与控水比较试验,运用双向电泳分析红麻在干旱胁迫和正常供水条件下叶片蛋白质组的动态变化。【结果】对2-DE图谱分析后发现,在干旱胁迫下出现65个差异表达蛋白质点,选用表达量明显上调的9个蛋白质点,通过MALDI-TOF-TOF MS分析和数据库检索,鉴定出6个差异表达蛋白的功能,分别是2个核酮糖-1,5-二磷酸羧化酶（Rubisco）或其大亚基（所有植物进行光合碳同化的关键酶）、1个Rubisco活化酶（广泛存在于植物中调节Rubisco活性的酶）、1个二甲基萘醌甲基转移酶（一种参与甲基转移反应的辅酶）、1个推定的胞质型谷氨酰胺合成酶（参与高等植物氨同化过程的关键酶）、1个ATP合酶β亚基（在活性细胞中起着将其它能量合成为生物能量通货-ATP的能量转换作用）。【结论】揭示了红麻GA42表现出较强的耐旱性与上述6个差异表达蛋白质点明显上调有关。     

Soap bubbles: two years old and sixty centimeters in diameter

Soap bubbles of long life (over 2 years) and large size (over 60 centimeters in diameter, 100 liters volume) have been produced from bubble solutions improved by the addition of water-soluble synthetic organic polymers such as polyvinyl alcohol or polyoxyethylene. The natural life can be defined as the time it takes for the bubble, if left undisturbed, to contract from the original size to a flat film.     

Large odd-numbered carbon clusters from fullerene-ozone reactions

The odd-numbered carbon clusters C(119), C(129), and C(139) have been observed in the mass spectra of toluene extracts of fullerene soots and of the products of ozone-fullerene reactions. Specifically, ozone-C(60) reactions yield C(119), ozone-C(70) reactions yield C(139), and ozone-(C(60)/C(70)) reactions produce C(119), C(129), and C(139). These unexpected species correspond to dimers of C(60), C(60)/C(70), and C(70), respectively, less one carbon atom, and are stable gas-phase ions with behavior similar to that of fullerenes. The results suggest a new route to functionalization and derivatization of fullerenes through controlled ozone-catalyzed cage-opening reactions.     

Dynamics-driven reaction pathway in an intramolecular rearrangement

A critical role is traditionally assigned to transition states (TSs) and minimum energy pathways, or intrinsic reaction coordinates (IRCs), in interpreting organic reactivity. Such an interpretation, however, ignores vibrational and kinetic energy effects of finite temperature. Recently it has been shown that reactions do not necessarily follow the intermediates along the IRC. We report here molecular dynamics (MD) simulations that show that dynamics effects may alter chemical reactions even more. In the heterolysis rearrangement of protonated pinacolyl alcohol Me3C-CHMe-OH2+ (Me, methyl), the MD pathway involves a stepwise route with C-O bond cleavage followed by methyl group migration, whereas the IRC pathway suggests a concerted mechanism. Dynamics effects may lead to new interpretations of organic reactivity.     

Fluid processes in subduction zones

Fluids play a critical role in subduction zones and arc magmatism. At shallow levels in subduction zones (<40 kilometers depth), expulsion of large volumes of pore waters and CH(4)-H(2)O fluids produced by diagenetic and low-grade metamorphic reactions affect the thermal and rheological evolution of the accretionary prism and provide nutrients for deep-sea biological communities. At greater depths, H(2)O and CO(2) released by metamorphic reactions in the subducting oceanic crust may alter the bulk composition in the overlying mantle wedge and trigger partial melting reactions. The location and conse-quences of fluid production in subduction zones can be constrained by consideration of phase diagrams for relevant bulk compositions in conjunction with fluid and rock pressure-temperature-time paths predicted by numerical heat-transfer models. Partial melting of subducting, amphibole-bearing oceanic crust is predicted only within several tens of million years of the initiation of subduction in young oceanic lithosphere. In cooler subduction zones, partial melting appears to occur primarily in the overlying mantle wedge as a result of fluid infiltration.     

Two-step synthesis of carbohydrates by selective aldol reactions

Studies of carbohydrates have been hampered by the lack of chemical strategies for the expeditious construction and coupling of differentially protected monosaccharides. Here, a synthetic route based on aldol coupling of three aldehydes is presented for the de novo production of polyol differentiated hexoses in only two chemical steps. The dimerization of alpha-oxyaldehydes, catalyzed by l-proline, is then followed by a tandem Mukaiyama aldol addition-cyclization step catalyzed by a Lewis acid. Differentially protected glucose, allose, and mannose stereoisomers can each be selected, in high yield and stereochemical purity, simply by changing the solvent and Lewis acid used. The reaction sequence also efficiently produces (13)C-labeled analogs, as well as structural variants such as 2-amino- and 2-thio-substituted derivatives.     

Molecular transformations on single crystal metal surfaces

One of the primary objectives of modern surface chemistry of transition metals is the synthesis of surface compounds and complexes and the understanding of their reactivity, structure, and bonding. Such considerations are paramount for advancing understanding of catalysis, adhesion, organic thin-film growth, and electrocatalysis. On selected metals, particularly copper, silver, and gold, selective scission of X-H bonds (where X is oxygen, carbon, nitrogen, or sulfur) by surface-bound atomic oxygen occurs to form moderately stable species that can be isolated for further study. Selective oxidation reactions may occur heterogeneously by means of this novel oxygen- activated route. Furthermore, this selective chemistry offers a paradigm for synthesis of a wide variety of surface organometallic complexes, whose formation can be predicted from acid-base principles. These subjects are discussed in this article with emphasis on their role in catalytic oxidation cycles.     

浅谈雪茄烟晾制过程中的颜色变化

雪茄烟叶的颜色在晾制过程会由绿色-黄色-棕色或者褐色转化,这可能是由于色素降解或者烟叶内部发生了某些化学反应而造成的。现在对于雪茄烟晾制过程中的颜色变化还没有系统的解释。但现有大量研究是关于果蔬、饮料、面包等褐变的机理,从中整理得出几条原因：（1）与色素的降解有关;（2）与棕色化反应有关;（3）与膜脂过氧化作用有关。因此,本文从这几点出发,探讨关于雪茄烟晾制过程中颜色变化的原因。     

Sensitivity of leaf chlorophyll empirical estimators obtained at Sentinel-2 spectral resolution for different canopy structures

A comparison of the sensitivity of canopy scale estimators of leaf chlorophyll, obtainable with Sentinel-2 spectral resolution, to soil, canopy and leaf mesophyll factors, was addressed. The analysis of a synthetic dataset, generated simulating the reflectance in the 1–4 LAI range of canopies for the main general classes of leaf inclination (i.e. erectophile, plagiophile, spherical, planophile and extremophile) and for different soil types was used for such a purpose. The synthetic dataset was obtained using the PROSPECT5-4SAIL model in the direct mode with a large variety of soil backgrounds. Additionally an experimental dataset including airborne hyperspectral data gathered during ESA (European Space Agency) campaigns SPARC and AGRISAR, was employed to simulate Sentinel-2 spectral and spatial resolution, to confirm model results. Analysis of the synthetic and experimental datasets indicated that: (i) the CVI (Chlorophyll Vegetation Index), relying only on visible and NIR (Near Infra-Red) bands and obtainable at 10 m spatial resolution, can be used as leaf chlorophyll estimator, at growth stages suitable for nitrogen fertilizer topdressings, for all canopy structures except for erectophile canopies; (ii) better results can be obtained by using different indices for different leaf architectures, with TCI/OSAVI (Triangular Chlorophyll Index/Optimized Soil Adjusted Vegetation Index) performing better for erectophile canopies, whereas MTCI (MERIS Terrestrial Chlorophyll Index) provides better results for planophile canopies, despite the fact that these indices require bands obtainable at 20 m spatial resolution from Sentinel-2 data.     

2012-2014年某脑科医院药品不良反应分析及防治对策

目的 调查分析医院上报的药品不良反应（ADR）的特点与规律,探讨ADR的防治对策,为患者安全用药提供参考。方法 回顾性分析某脑科医院2012-2014年上报的ADR 579例,从患者的性别、年龄、药物品种、给药途径、不良反应累及器官、临床表现情况进行分析。结果 579例ADR中男性271例,女性308例。给药途径以静脉给药最多为313例（50.73%）,其次为口服254例（41.17%）。静脉给药与非静脉给药比较差异有统计学意义（P<0.01）。ADR药品种类中以精神障碍类药物最多为165例（28.25%）,其次是抗感染药物和中药制剂,分别为87例（14.89%）和77例（13.18%）。三者比较差异有统计学意义（P<0.01）。系统器官损害以皮肤及其附件最多为189例（32.6%）,其次为消化系统113例（19.5%）。结论 用药前应充分了解药物及患者的ADR情况,减少联合用药,谨慎使用静脉给药。选择合适的药物及给药方式,注意监测。     

2-羟基-4-甲基苯甲酸的合成

选择丙酮为起始原料,与甲酸乙酯进行缩合反应得到第一步反应产物甲酰丙酮;再与乙酰乙酸乙酯缩合合成目标化合物2-羟基-4-甲基苯甲酸.将终产物通过红外光谱、质谱、核磁共振进行检测,综合分析各波谱的检测结果,并与标准图谱进行比较,确定所合成产物为2-羟基-4-甲基苯甲酸.在产物的分离纯化上用pH梯度分离法,简化了合成工艺,得到了较高的产率.     

Catalytic hydration of terminal alkenes to primary alcohols

Direct catalytic hydration of terminal alkenes to primary alcohols would be an inexpensive route to industrially useful alcohols and a convenient synthetic route for the synthesis of terminal alcohols in general. The reaction between trans- PtHCl(PMe(3))(2) (where Me = CH(3)) and sodium hydroxide in a one-to-one mixture of water and 1-hexene yields a species that, at 60 degrees C and in the presence of the phasetransfer catalyst benzyltriethylammonium chloride, catalyzes selective hydration of 1-hexene to n-hexanol at a rate of 6.9 +/- 0.2 turnovers per hour. Hydration of 1-dodecene to n-dodecanol occurs at a rate of 8.3 +/- 0.4 turnovers per hour at 100 degrees C. Deuterium labeling experiments with trans-PtDCl(PMe(3))(2) show that hydration involves reductive elimination of a C-H bond. At low hydroxide concentrations (<8 equivalents), hydration of the water-soluble olefin 3-butene-1-ol to 1,4-butanediol exhibited a first-order dependence on hydroxide concentration for loss of catalytic activity. This suggests that hydroxide attacks the coordinated alkene slowly. At high hydroxide concentrations, the rate of catalysis was hydroxide-independent and first order in alkene. Substitution of coordinated water (k(1) = 9.3 +/- 0.5 x 10(-3) liters per mol per second) appears to be limitng under these conditions.     

Gaussian free-energy dependence of electron-transfer rates in iridium complexes

The kinetics of photoinduced electron-transfer (ET) reactions have been measured in a series of synthetic donor-acceptor complexes. The electron donors are singlet or triplet excited iridium(I) dimers (Ir(2)), and the acceptors are N-alkylpyridinium groups covalently bound to phosphinite ligands on the Ir(2) core. Rate constants for excited-state ET range from 3.5 x 10(6) to 1.1 x 10(11) per second, and thermal back ET (pyridinium radical to Ir(2)(+)) rates vary from 2.0 x 10(10) to 6.7 x 10(7) per second. The variation of these rates with driving force is in remarkably good agreement with the Marcus theory prediction of a Gaussian free-energy dependence.     

家兔A型魏氏梭菌病病因及防治报告

本文通过对河北省A、B两兔场暴发家兔A型魏氏梭菌病病因的调查分析和治疗试验,得出如下结论:(1)该病诱因是饲料营养失调,高能量、高蛋白、低纤维,速成后肠碳水化合物过度负荷所致。长途运输、饲料更换、冷潮刺激等也是该病的诱因。(2)该病死因主要是由于魏氏梭菌外毒素导致神经系统中毒、肠道粘膜严重损伤和极度脱水所致。(3)该病主要症状是急性水样腹泻,体温正常或偏低。病变主要是肓肠出血和胃粘膜溃疡。(4)采取大剂量口服青、链霉素、补液、解毒和收敛等综合措施,可控制病情发展,并使轻症群治愈率76.67%,重症群52.63%,病危群9.38%。     

人工合成小麦对白粉病的抗性评价

本研究利用我国不同地区的20个小麦白粉菌菌株对28份合成小麦材料进行抗病性评价,并利用与基因连锁的分子标记检测这些合成小麦中Pm2抗白粉病基因。在供试的合成小麦材料中,C7、C14和C2分别抗14～16个菌株,另有6份材料能抗10个以上菌株,C16和C20不抗任何菌株。来自相同杂交组合的材料抗病性表现有很大不同。根据分子检测的结果,C9和C19的扩增片段与Pm2基因相同,但是抗谱分析表明这两个合成小麦对白粉菌的反应型与Pm2基因不同。     

Ion cyclotron resonance spectroscopy. Cyclotron double resonance provides a new technique for the study of ion-molecule reaction mechanisms

Ion cyclotron resonance spectroscopy yields information on many aspects of ion-molecule chemistry. The method is ideally suited for experiments involving ion energies below several electron volts, and hence provides a valuable complement to other techniques (27). eyclotron double resonance is uniquely suitable for establishing relationships between reactant ions and their product ions in complex ion-molecule reaction sequences. The double-resonance experiments with isotopic species yield information on reaction mechanisms and the nature of intermediate species. Ion-molecule reactions which occur at low energies are quite sensitive to the nature of functional groups and the details of molecular structure (28). Reactions of ions or neutral molecules with specific reagents in the cyclotron spectrometer can thus be used to characterize unknown species. Once the systematic ion-molecule chemistry of useful reagents has been worked out, it should be possible to proceed in a manner directly analogous to classical chemical methods. Suppose, for example, that reagents A(+), B(+), C(+), and D(+) each have characteristic reactions with different functional groups. Then these reagents can all be mixed with an unknown neutral species, X, and each of the reactions, X + A(+) --> ?, X + B(+) --> ?, . . . . can be examined. In contrast to solution chemistry, all the reagents can be added simultaneously to the unknown, since each of the specific reactions can be examined by cyclotron double resonance. The reactions which occur, the species synthesized , and the products of degradation then characterize X. The same methodology can be applied to characterize an unknown ionic epecies X(+), through use of neutral reagents A, B, C, and D. For example, proton transfer reactions to neuteal species have been applied in studying ions of mass 45 produced from various sources (29). The order of the proton affinities of the neutral reagent molecules are as follows: NH(3) isobutylene propene. Ions of mass 45 can be produced by the protonation of ethylene oxide (see structure III), the protonation of acetaldehyde (see structure IV), and the fragmentation of dimethyl ether (see structure V). Those ions might be expected to have, respectively, the three structures: Proton transfer from the mass-45 ions from sources III and IV to NH(3) and to isobutylene occurs readily, but not proton transfer to propene. For the ion from source V, proton transfer to NH3 occurs, but not proton transfer to isobutylene or propene. Thus the proton transfer reactions to various neutral reagents demonstrate that the mass-45 ions from the various sources are different. This example is only a rudimentary version of an approach to the characterization of unusual ionic species; niore sophisticated applications can follow when the systematic chemistry of more reagents is available. This approach should be ideal for comparing nonclassical carbonium ions produced by different routes. Some very interesting ionic species are produced by rearrangements in the fragmentation of molecules, following electron impact. Such molecular rearrangements frequently result in the fragmentation of an ion radical to another ion radical with the elimination of a small neutral species (30). It should be possible to run these reactions in reverse to check the postulated mechanisms. An interesting result of the systematic study of proton transfer to various functional groups is the finding that the proton affinity of various amines and pyridine is extremely high (31). Species such as VI and VII: might be expected to be very stable; they are in fact so stable that they are unreactive with respect to subsequent chemistry at the charge center. Thus, if there are other functional groups on the ion, the important reactions should occur at these functional groups. It should be possible to design species for which the presence of the charge has little influence on the reactivity of a neutral functional group. In this case the charge functions simply as an inert label which makes the study of neutral-neutral reactions accessible by cyclotron resonance: Various routes for development of the basic technique also appear to be very promising. Echo phenomena following sequences of pulsed excitation have been observed in electron cyclotron resonance (32). Analogous transient phenomena should also occur in ion cvclotron resonances (33). Pulsed-cyclotron-resonance techniques of course have intriguing analogies to nuclear-magnetic-resonance spin-echo experiments (34) and may be the technique of choice for making accurate measurements of ion-molecule-reaction cross sections as a function of energy for low ion energies. Finally, many ion-molecule reactions yield products in excited electronic states (35). For example, the reaction N(2)- + CO --> N(2) + CO- (46) has been studied by beam techniques (36). A straightforward procedure is to observe optical emission from the cyclotron spectrometer by placing a window at the end of the cyclotron cell (37). The emission can be analyzed with a crude set of optical filters, or with a high-speed spectrograph. Optical emission from the cyclotron cell can of course originate from many sources. The radiation from a specific excited product ion can be selected by a radio-frequency-optical double-resonance experiment. If, in the generai reaction A+ + B --> *C+ + D, (47) ion A+ is irradiated at its cyclotron resonance frequency, the number density of optical emitters *C+ is changed. If the irradiating frequency is modulated, then the number of optical emitters will be modulated, so that the intensity of emission from *C+ will also be modulated. When the optical emission from *C+ is analyzed in a spectrograph with a photoelectric cell, the output of the photoelectric cell can be detected with a phase sensitive detector referenced to the modulation frequency. This highly specific modulation-detection scheme should discriminate against other sources of light in the cyclotron cell.     

Postseismic mantle relaxation in the Central Nevada Seismic Belt

Holocene acceleration of deformation and postseismic relaxation are two hypotheses to explain the present-day deformation in the Central Nevada Seismic Belt (CNSB). Discriminating between these two mechanisms is critical for understanding the dynamics and seismic potential of the Basin and Range province. Interferometric synthetic aperture radar detected a broad area of uplift (2 to 3 millimeters per year) that can be explained by postseismic mantle relaxation after a sequence of large crustal earthquakes from 1915 to 1954. The results lead to a broad agreement between geologic and geodetic strain indicators and support a model of a rigid Basin and Range between the CNSB and the Wasatch fault.