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手性固定相-高效液相色谱法在手性药物、手性农药等的分离分析中应用广泛。本文采用3种多糖衍生物的手性固定相(即EnantioPak AD、AS和OD)对20种手性化合物开展手性分离研究,进而探讨样品分子结构、多糖骨架和衍生基团对手性分离的影响。结果表明,除化合物13外,其余化合物在EnantioPak AD上均实现基线分离,分离度多在2.0以上,在正己烷-醇流动相中加入酸碱添加剂可改善和优化酸性或碱性化合物的分离效果;芳香醇(化合物13~16)随着侧链碳数增加在色谱柱上的保留减弱,其分离度呈现增加的趋势;对比8种化合物在3种手性固定相上的分离结果可知,EnantioPak AD表现出更优的分离性能。这为深入研究和了解多糖手性固定相、拓展其手性分离应用提供了参考。 相似文献
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CHIRALCEL OD手性柱直接拆分萘普生对映体 总被引:1,自引:0,他引:1
以CHIRALCELOD为固定相,建立了在正相条件下直接拆分萘普生对映体的HPLC方法。考察了流动相组成、流速、进样量和温度等因素对对映体分离的影响。优化后的色谱条件为:CHIRACELOD色谱柱(250mm×4.6mm,10μm);流动相:正己烷-异丙醇-冰醋酸(97∶3∶1,V/V);流速:1.0mL/min;紫外检测波长:254nm;柱温:35℃。在此条件下,萘普生对映体可得到基线分离。此方法可用于S-萘普生制备时酶膜反应器中萘普生甲酯动态拆分过程的跟踪分析。 相似文献
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Adiabatic (1A' or 1A' state) and non-adiabatic (2A'/1A' states) quantum dynamics calculations have been carried out for the title reaction (O((1)D) + D(2) → OD + D) to obtain the initial state-specified (v(i) = 0, j(i) = 0) integral cross section and rate constant using the potential energy surfaces of Dobbyn and Knowles. A total of 50 partial wave contributions have been calculated using the Chebyshev wave packet method with full Coriolis coupling to achieve convergence up to the collision energy of 0.28 eV. The total integral cross section and rate constant are in excellent agreement with experimental as well as quasi-classical trajectory results. Contributions from the adiabatic pathway of the 1A' state and the non-adiabatic pathway of the 2A'/1A' states, increase significantly with the collision energy. Compared to the O((1)D) + H(2) system, the kinetic isotope effect (k(D)/k(H)) is found to be nearly temperature independent above 100 K and its value of 0.77 ± 0.01 shows excellent agreement with the experimental result of 0.81. 相似文献
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Lehman JH Dempsey LP Lester MI Fu B Kamarchik E Bowman JM 《The Journal of chemical physics》2010,133(16):164307
We report joint experimental and theoretical studies of outcomes resulting from the nonreactive quenching of electronically excited OD?A (2)Σ(+) by H(2). The experiments utilize a pump-probe technique to detect the OD?X (2)Π product state distribution under single collision conditions. The OD?X (2)Π products are observed primarily in their lowest vibrational state (v(") = 0) with substantially less population in v(") = 1. The OD?X (2)Π products are generated with a high degree of rotational excitation, peaking at N(") = 21 with an average rotational energy of 4600 cm(-1), and a strong propensity for populating the Π(A(')) Λ-doublet component indicative of alignment of the half-filled pπ orbital in the plane of OD rotation. Branching fraction measurements show that the nonreactive channel accounts for less than 20% of quenching outcomes. Complementary classical trajectory calculations of the postquenching dynamics are initiated from representative points along seams of conical intersections between the ground and excited-state potentials of OD(A (2)Σ(+),X (2)Π) + H(2). Diabatic modeling of the initial momenta in the dynamical calculations captures the key experimental trends: OD?X (2)Π products released primarily in their ground vibrational state with extensive rotational excitation and a branching ratio that strongly favors reactive quenching. The OD?A (2)Σ(+) + H(2) results are also compared with previous studies on the quenching of OH?A (2)Σ(+) + H(2); the two experimental studies show remarkably similar rotational energy distributions for the OH and OD?X (2)Π radical products. 相似文献
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采用准经典轨线方法讨论了反应物分子的振动激发对O+DCl→OD+Cl反应动力学性质的影响.计算结果表明,反应物分子的振动激发对(2π/σ)(dσ00/dωt),(2π/σ)(dσ20/dωt)和(2π/σ)(dσ22+/dωt)3个极化微分反应截面和产物分子转动角动量取向程度的影响比较显著.变化规律反映出反应物分子的高振动激发使产物分子倾向于在平行于散射面的平面内转动. 相似文献
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本文用红外光谱法考察了CD_3OD 在改性前后的HZSM-5催化剂上的吸附作用,提出了其吸附态模型及吸附机理。发现当CD_3OD 吸附在HZSM-5与Al 改性的HZSM-5(简称AlHZSM-5)后,于180—200℃下抽空20分钟,均有甲氧基生成,而在300℃左右抽空20分钟,则甲氧基脱除,B 酸中心的吸收峰再现。在Mg 改性的HZSM-5催化剂(简称Mg HZSM-5)上则大不相同,所吸附的CD_3OD 在各种温度下脱附时均未发现有甲氧基生成;在200—550℃范围内,这些催化剂的红外谱图上在2000—2300cm~(-1)区间还出现强弱不等的CD 伸缩振动吸收峰,这可能是由于吸附在强的L 酸中心上的CD_3OD 或CD_3OCD_3引起的。 相似文献
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The rovibrational state distributions and state-resolved scattering distributions of CD(3) radicals produced by the reaction O((1)D) + CD(4) were investigated by crossed molecular beam ion imaging. The rotational structure of the resonance-enhanced multiphoton ionization spectrum of CD(3) in the ground vibrational state indicates that the low K rotational states of CD(3) radicals are preferentially populated. The state-resolved scattering distributions of CD(3) (v = 0) and those of the excited states of the out-of-plane bending (v(2)) mode exhibit a structureless forward-scattering component due to an insertion pathway and a structured backward-scattering component due to an abstraction path. The scattering distributions of CD(3) in the excited state of the C-D symmetric stretch (v(1)) do not exhibit the abstraction component. The scattering distribution of the abstraction component gradually extends in the forward direction with increasing intensity as the v(2) vibration becomes more strongly excited. This suggests that abstraction with a larger impact parameter results in stronger excitation of v(2). 相似文献
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The quasi-classical trajectory calculation for the reaction O(1D)+HD is carried out based on the Dobbyn and Knowles potential energy surface. In this work, the reaction cross section and product branching ratio are obtained. The product branching ratio OD/OH was discussed. The calculated results show that the cross-section decreases thoroughly with the increasing of the collision energy from 4.6 kJ/mol to 46.0 kJ/mol. The average branching ratio decrease with the increase of rotational quantum number of reactant HD. 相似文献
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Cheng L Yuan K Cheng Y Guo Q Wang T Dai D Yang X Dixon RN 《The journal of physical chemistry. A》2011,115(9):1500-1507
The dissociation dynamics of HOD via two-photon excitation to the C? state have been investigated using the H-atom Rydberg tagging time-of-flight (TOF) technique. The H-atom action spectrum for the C? ← X? transition shows resolved rotational structure. Product translational energy distributions and angular distributions have also been recorded for the H + OD channel for three excited levels each with k(a)′ = 2. From these distributions, quantum state distributions and angular anisotropy parameters (β2 and β4) for the OD product were determined. These results are consistent with the nonadiabatic predissociation picture illustrated in the one-photon dissociation process for H2O. The heterogeneous dissociation pathway via Coriolis coupling is the dominant dissociation process in the present study. A high proportion of the total available energy is deposited into the rotational energy of the OD product. The anisotropic recoil distributions reveal the distinctive contributions from the alignment of the excited states and the dissociation process. Comparisons are also made between the results for HOD and H2O via the equivalent rotational transitions. The OH bond energy, D(o)(H?OD), of the HOD molecule is also determined to be 41283.0 ± 5 cm(-1). 相似文献
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The H- and D-atom products from collisional quenching of OD A (2)Σ(+) by H(2) are characterized through Doppler spectroscopy using two-photon (2 (2)S ←← 1 (2)S) laser-induced fluorescence. Partial deuteration enables separation of the channel forming H + HOD products, which accounts for 75% of reactive quenching events, from the D + H(2)O product channel. The Doppler profiles, along with those reported previously for other isotopic variants, are transformed into product translational energy distributions using a robust fitting procedure based on discrete velocity basis functions. The product translational energy distribution for the H-atom channel is strongly peaked at low energy (below 0.5 eV) with a long tail extending to the energetic limit. By contrast, the D-atom channel exhibits a small peak at low translational energy with a distinctive secondary peak at higher translational energy (approximately 1.8 eV) before falling off to higher energy. In both cases, most of the available energy flows into internal excitation of the water products. Similar distributions are obtained upon reanalysis of D- and H-atom Doppler profiles, respectively, from reactive quenching of OH A (2)Σ(+) by D(2). The sum of the translational energy distributions for H- and D-atom channels is remarkably similar to that obtained for OH A (2)Σ(+) + H(2), where the two channels cannot be distinguished from one another. The product translational energy distributions from reactive quenching are compared with those obtained from a previous experiment performed at higher collision energy, quasiclassical trajectory calculations of the post-quenching dynamics, and a statistical model. 相似文献
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用从头算方法, 获得了H2O + Cl→HCl + OH(R1), HOD +Cl→DCl + OH(R2), HOD + Cl→HCl + OD(R3)反应的内禀反应坐标(IRC)。根据传统过渡态、变分过渡态理论及相应的隧道效应校正, 计算了反应的速率常数。对已有实验速率常数值的R1反应, 我们计算的结果和实验一致。根据Truhlar的振动选态公式, 分别讨论了激发HOD中OH, OD振动模式对反应速率的影响,得到激发HOD中的OH振动模式将有利于产物OD + HCl生成, 和实验的结论相一致。 相似文献
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Differential Cross Sections for the H+D2O→HD+OD Reaction: a Full Dimensional State-to-State Quantum Dynamics Study 下载免费PDF全文
The time-dependent wave-packet method was employed to calculate the first full-dimensional state-to-state differential cross sections (DCS) for the title reaction with D2O in the ground and the first symmetric (100) and asymmetric stretching (001) excited states. The calculated DCSs for these three initial states are strongly backward peaked at low collision energies. With the increase of collision energy, these DCSs become increasingly broader with the peak position shifting gradually to a smaller angle, consistent with the fact that the title reaction is a direct reaction via an abstraction mechanism. It is found that the (100) and (001) states not only have roughly the same integral cross sections, but also have essentially identical DCS, which are very close to that for the ground state at the same total energy of reaction. The reaction produces a small fraction of OD in the v=1 state, with the population close to the relative reactivity between the ground and vibrationally excited states, therefore confirming the experimental result of Zare et al. and the local mode picture[J. Phys. Chem. 97 , 2204 (1993)]. Unexpectedly, the stretching excitation reduces the rotation excitation of product HD at the same total energy. 相似文献
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Theoretical investigations on the stereodynamics of the O(3P)+D2 reaction have been calcu-lated by means of the quasi-classical trajectory to study the product rotational polarization at collision energy of 104.5 kJ/mol on the potential energy surface of the ground 3A" triplet state. The vector properties including angular momentum alignment distributions and four polarization dependent generalized differential cross-sections of product have been presented. Furthermore, the influence of reagent vibrational excitation on the product vector properties has also been studied. The results indicate that the vector properties are sensitively affected by reagent vibrational excitation. 相似文献
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研究了s1p1组态能级位置及能级劈裂同基质的关系. 结果表明, Sn2+的A、B、C带能级和In+、Tl+的A、B带能级位置同基质的环境因子he呈线性关系, 能级能量随he的增大而减小, 给出了相应的经验公式, 并计算了In+和Tl+自由离子的A、B带能级能量. 计算结果同实验数据十分吻合, 最大的偏差来自Tl+的B带, 偏差率仅为-7.34%. 随基质he的增大, 高能级能量比低能级下降得更快, A、B和C带间的能级间距相应变小. 通过对比发现: Sn2+、In+、Tl+的A、B带能级对基质的敏感性存在较大差异, Sn2+能级能量受基质变化影响最大, In+的能级能量随基质变化最小. 更为重要的是, 发现随着he的增大, Sn2+、In+和Tl+的A、B和C带能级劈裂相应变小, 甚至不再劈裂, 很好地解释了光谱现象. 相似文献