Theoretical survey of the potential energy surface of methyl nitrite + Cu+ reaction

The gas-phase reaction of methyl nitrite with Cu+ has been investigated using density functional theory. The geometries and energies of all the stationary points involved in the reaction have been investigated at the B3LYP/6-311+G(2df,2pd) level. Seven different structures of the encounter complexes could be formed when Cu+ attacking at different electronegative heteroatoms of trans and cis conformational isomers of methyl nitrite, in which the inner oxygen attacks account for the most stable complexes. Extensive conversions could take place for these complexes converting into each other. Various mechanisms leading to the loss of NO and HNO are analyzed in terms of the topology of the potential energy surface. The reaction proceeds exclusively from the inner oxygen attachments, followed by four different mechanisms, i.e., direct dissociation, direct H abstraction, N-O activation, and C-H activation, where the former two provide direct channels for the respective losses of NO and HNO, the third one accounts for both of the losses, and C-H activation is unlikely to be important due to the energetics.     

Theoretical analysis of the conversion mechanism of acetylene to ethylidyne on Pt(111)

The conversion of acetylene to ethylidyne on Pt(111) has been comprehensively investigated using self-consistent periodic density functional theory. Geometries and energies for all of the intermediates involved as well as the conversion mechanism were analyzed. On Pt(111), the carbon atoms in the majority of stable C(2)H(x) (x = 1-4) intermediates prefer saturated sp(3) configurations with the missing H atoms substituted by the adjacent metal atoms. The most favorable conversion pathway for acetylene to ethylidyne is via a three-step reaction mechanism, acetylene → vinyl → vinylidene → ethylidyne. The first step, acetylene → vinyl, depends on the availability of surface H atoms: without preadsorbed H the reaction occurs via the initial disproportionation of acetylene, which resulted in adsorbed vinyl; with an abundance of preadsorbed H, acetylene could transform to vinyl via both the disproportionation and hydrogenation reactions. Conversions through initial dehydrogenation of acetylene and isomerizations of acetylene and vinyl are unfavorable due to high energy barriers along the relevant pathways. The conversion rate involving vinylidene as an intermediate is at least 100 times larger than that involving ethylidene.     

中子数字成像FPGA抗辐照技术研究

中子数字成像试验中,现场可编程门阵列（FPGA）是重要的成像逻辑控制器件。然而,中子辐照易引起FPGA的单粒子效应,对中子成像引入本底噪声,因此必须采取措施,减少中子辐照对FPGA成像的影响。结合图像周期性的特点,采用三判二的技术方法替代三模冗余,裁决成像关键信号;采用硬件实现的中值滤波算法,平滑由于RAM区单粒子翻转等原因呈现在图像上的噪点。仿真结果表明,本文采用的两种技术方法不但降低资金成本,提高FPGA资源冗余度,而且在取得良好的抗辐照滤波效果的同时,保留图像细节。时序仿真和硬件平台验证了设计的正确性。     

Synthesis of Copolymers of Methacrylate BearingAminonitro┐StilbeneDyesandTheirNonlinearOpticalProper

报道了含ａｍｉｎｏｎｉｔｒｏ－ｓｔｉｌｂｅｎｅ基团的甲基丙烯酸酯类单体的合成、该单体与ＭＭＡ的共聚反应及对所得聚合物进行的非线性光学性能测定。结果表明，缩短ｓｔｉｌｂｅｎｅ片段与甲基丙烯酰基的连接链长有助于改善单体的聚合性能，增强聚合物在有机溶剂中的溶解能力。对所得聚合物的ＳＨＧ测定显ｄ３３值可达到５４ｐｍ／ｖ。     

Unimolecular dissociation of protonated trans-1,4-diphenyl-2-butene-1,4-dione in the gas phase: rearrangement versus simple cleavage

Fragmentation mechanisms of trans-1,4-diphenyl-2-butene-1,4-dione were studied using a variety of mass spectrometric techniques. The major fragmentation pathways occur by various rearrangements by loss of H(2)O, CO, H(2)O and CO, and CO(2). The other fragmentation pathways via simple alpha cleavages were also observed but accounted for the minor dissociation channels in both a two-dimensional (2-D) linear ion trap and a quadrupole time-of-flight (Q-TOF) mass spectrometer. The elimination of CO(2) (rather than CH(3)CHO or C(3)H(8)), which was confirmed by an exact mass measurement using the Q-TOF instrument, represented a major fragmentation pathway in the 2-D linear ion trap mass spectrometer. However, the elimination of H(2)O and CO becomes more competitive in the beam-type Q-TOF instrument. The loss of CO is observed in both the MS(2) experiment of m/z 237 and the MS(3) experiment of m/z 219 but via the different transition states. The data suggest that the olefinic double bond in protonated trans-1,4-diphenyl-2-butene-1,4-dione plays a key role in stabilizing the rearrangement transition states and increasing the bond dissociation (cleavage) energy to give favorable rearrangement fragmentation pathways.     

Gas-phase Meerwein reaction of epoxides with protonated acetonitrile generated by atmospheric pressure ionizations

Ethylnitrilium ion can be generated by protonation of acetonitrile (when used as the LC-MS mobile phase) under the conditions of atmospheric pressure ionizations, including electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) as well as atmospheric pressure photoionization (APPI). Ethylnitrilium ion (CH₃ - C o mathop N⁺ HCH_3 - C equiv mathop Nlimits^ + H and its canonical form CH₃ - mathop C⁺ = NHCH_3 - mathop Climits^ + = NH) is shown to efficiently undergo the gas-phase Meerwein reaction with epoxides. This reaction proceeds by the initial formation of an oxonium ion followed by three-to-five-membered ring expansion via an intramolecular nucleophilic attack to yield the Meerwein reaction products. The density functional theory (DFT) calculations at the B3LYP/6-311 + G(d,p) level show that the gas-phase Meerwein reaction is thermodynamically favorable. Collision-induced dissociation (CID) of the Meerwein reaction products yields the net oxygen-by-nitrogen replacement of epoxides with a characteristic mass shift of 1 Da, providing evidence for the cyclic nature of the gas-phase Meerwein reaction products. The gas-phase Meerwein reaction offers a novel and fast LC-MS approach for the direct analysis of epoxides that might be of genotoxic concern during drug development. Understanding and utilizing this unique gas-phase ion/molecule reaction, the sensitivity and selectivity for quantitation of epoxides can be enhanced.     

Initial hydrogenations of pyridine on MoP(001): a density functional study

The initial hydrogenations of pyridine on MoP(001) with various hydrogen species are studied using self-consistent periodic density functional theory (DFT). The possible surface hydrogen species are examined by studying interaction of H(2) and H(2)S with the surface, and the results suggest that the rational hydrogen source for pyridine hydrogenations should be surface hydrogen atoms, followed by adsorbed H(2)S and SH. On MoP(001), pyridine has two types of adsorption modes, i.e., side-on and end-on; and the most stable η(5)(N,C(α),C(β),C(β),C(α)) configuration of the side-on mode facilitates the hydrogenation of pyridine. The optimal hydrogenation path of pyridine with surface hydrogen atoms in the Langmuir-Hinshelwood mechanism is the formation of 3-monohydropyridine, followed by producing 3,5-dihydropyridine, in which the two-step hydrogenations take place on the C(β) atoms. When adsorbed H(2)S is considered as the source of hydrogen, slightly higher hydrogenation barriers are always involved, while the energy barriers for hydrogenations involving adsorbed SH are much lower. However, the hydrogenation of pyridine should be suppressed by the adsorption of H(2)S, and the promotion effect of adsorbed SH is limited.     

应用腙作为配体的铜催化二芳醚合成反应

一种简单易得的腙,2-吡啶醛 1-苯基腙 （1）,能够作为有效配体,极大地促进碘化铜催化的芳基溴与酚的C–O偶联反应。该偶联反应条件温和（二氧六环为溶剂、磷酸钾为碱、90–100 0C 的反应温度）,适用于各种芳基溴（电中性、贫电子和富电子）和酚（电中性和富电子）的底物,能够相容一些碱敏感官能团如酯基、醛基和羰基等。     

Chiral quantification of D-, L-, and meso-tartaric acid mixtures using a mass spectrometric kinetic method

Accurate quantification of the optical isomers in a ternary mixture of D-, L-, and meso-tartaric acids is achieved using electrospray ionization tandem mass spectrometry for in-situ metal complex formation and a three-point calibration method to quantify the dissociation kinetics.