活泼氢的核磁共振氢谱

核磁共振氢谱是有机化合物结构表征中最常使用的波谱方法之一,提供了有机化合物质子的化学位移、积分面积和耦合裂分等信息。常见的活泼氢是与氧、氮和硫共价相连的氢原子,存在着快速交换机制,与碳上的氢有显著的差异。在不同条件下活泼氢化学位移不固定、峰形多变并且耦合裂分情况复杂。本文探讨了如何通过核磁共振氢谱解析活泼氢,培养学生对谱图进行观察、分析以及结构推导的能力。     

二阶导数差示脉冲极法用于醋酸氟氢可的松的定量研究

用二阶导数差示脉冲极谱法对醛酸氟氢松进行了定量分析。在０．００１ｍｏｌ／Ｌ硫酸＋乙醇＋水（１＋２５＋２４）的底液中，醋酸氟氢可的松于－０．３４０Ｖ处出现一良好的二阶导数差示脉冲极谱，在５－１４０μｇ／ｍＬ范围内，醋酸氟氢可的松的浓度与其二阶导数差示脉冲极谱峰幅值呈线性关系，检测限为０．４ｎｇ／ｍＬ。本法操作简单、快速、灵敏、结果准确。     

杂环化合物氢交换的核磁共振研究

芳香族化合物在酸的作用下可发生可逆的氢交换。该过程是质子对芳香环作亲电进攻,生成过渡态的芳烃离子,后者再失去氢离子完成了氢的化学交换,因而本质是亲电取代反应。例如某些简单的芳香族化合物用重水     

从核磁共振氢谱推导的重质油氢碳原子摩尔比计算式

通过对炼油厂的催化油浆、重催油浆和催化重焦蜡油核磁共振氢谱中质子归属和重质油结构的假设，推导出计算这3种重质油的氢碳原子摩尔比计算式；结果表明，氢碳原子摩尔比的计算值与实测值非常接近，平均误差仅为3．1％。     

二阶导数差示脉冲极谱法用于醋酸氟氢可的松的定量研究

用二阶导数差示脉冲极谱法对醋酸氟氢可的松进行了定量分析。在０．００１ｍｏｌ／Ｌ硫酸＋乙醇＋水（１＋２５＋２４）的底液中，醋酸氟氢可的松于－０．３４０Ｖ（ｖｓＡｇ／ＡｇＣｌ）处出现一良好的二阶导数差示脉冲极谱峰，在５～１４０μｇ／ｍＬ范围内，醋酸氟氢可的松的浓度与其二阶导数差示脉冲极谱峰幅值呈线性关系，检测限为０．４ｎｇ／ｍＬ。本法操作简便、快速、灵敏、结果准确。     

光合细菌Chromatium vinosum可溶性氢酶的EPR研究

光合细菌 Chromatium vinosum可溶性氢酶经 5次柱层析 ( DE-2 3,TSK-DEAE( ) ,Ultragel Ac A-4 4 ,TSK-DEAE( ) ,Superdex TM75 )分离后被纯化 365倍 ,得率为 32 % ,其催化放氢的活性为 8.4μmol H2 /( min· mg prot) .氧化态可溶性氢酶在 4 5 K下 ,产生了 Ni( )的典型 EPR信号 ( gx,y,z=2 .37,2 .1 6,2 .0 1 6和 gx,y,z=2 .30 ,2 .2 3,2 .0 1 6) ;在 1 0 K下 ,没有出现膜结合态氢酶中存在的 [3Fe-4 S]簇特征 EPR信号 .可溶性氢酶被 H2 还原后 ,Ni( )的特征 EPR信号消失 ,同时出现一个 [4 Fe-4 S]簇的特征 EPR信号 ( gx,y,z=1 .88,1 .90 ,2 .0 4 5 ) .研究结果表明 ,C.vinosum可溶性氢酶在结构和功能上不同于膜结合态氢酶 ,是一种新的催化放氢的 Ni Fe-氢酶     

三氟乙烷与氟原子氢提取反应的动力学研究

采用双水平直接动力学方法研究了氢提取反应CH3CF3+F→CH2CF3+HF的反应机理.首先用MPW1K/6-311+G(d,p)方法优化了驻点的几何构型,并在相同水平上进行了频率分析,利用内禀反应坐标理论获得了最小的反应能量途径;随后,为了得到更准确的能量信息,采用MCG3-MPWPW91//MPW1K方法进行了单点能量校正;最后,根据变分过渡态理论计算了该反应在200² 000K温度范围内的速率常数.结果表明,理论计算值与已有的实验值吻合.     

核磁共振氢谱的计算机辅助解析——Ⅰ.高分子核磁共振氢谱的智能解析系统

本文报道了一种用于高分子类核磁共振氢谱解析的智能系统。系统以人们解析图谱的经验和思路为基础,结合高分子类核磁共振氢谱的特征和规律设计而成。系统由知识库、图谱库和推理机三部分组成,能模拟人们的思路,对未知高分子的核磁共振氢谱进行多层次的解析。系统采用Turbo Prolog 2.0语言编写,经在IBMPC/XT机上运行得到了令人满意的结果。     

担载铕催化剂氢还原的穆斯堡尔谱研究

使用原位穆斯堡尔谱考察了γ－Ａｌ２Ｏ３、ＳｉＯ２、ＴｉＯ２和ＺｒＯ２等几种载体担载的氧化铕催化剂的还原性。非担载Ｅｕ２Ｏ３很难在Ｈ２中原，而Ｅｕ２Ｏ３与γ－Ａｌ２Ｏ３、ＳｉＯ和ＴｉＯ２间存在着强相互作用，担载在这些载体上的Ｅｕ２Ｏ３在７７３Ｋ左右Ｈ２中处理可有不同程度的还原，其还原度反映了相互作用的强弱，为：Ｅｕ／γ－Ａｌ２Ｏ３＞Ｅｕ／ＴｉＯ２＞Ｅｕ／ＳｉＯ２＞Ｅｕ／ＺｒＯ２、Ｅｕ／ＺｒＯ２不能在     

芳香寡聚磺酸酯桥联大环化合物的合成和紫外光谱

以芳香二磺酰氯和芳香二酚为原料,三乙胺作缚酸剂,二氯甲烷作溶剂,采取一步成环法合成了一系列新型的、芳环单元不同的芳香寡聚磺酸酯桥联大环化合物。 合成产物的结构用IR、¹H NMR、¹³C NMR和MALDI-TOF等技术手段进行了确认。 并对合成方法、紫外光谱和变温核磁结构研究进行了有价值的探讨。 化合物3~5的DMF溶液的最大紫外吸收峰在266 nm处,化合物6在267 nm处,摩尔吸光系数分别是4.65×10⁴、5.61×10⁴、5.09×10⁴和9.98×10⁴ L/(mol·cm);检出限分别是2.15×10^-7、1.78×10^-7、1.96×10^-7和1.00×10^-7 mol/L。 变温核磁数据证明,苯环上连有支链有利于固定构象,可以通过这种方法合成结构固定的杯芳烃。     

The tetrazole–azide tautomerism of some nitrotetrazolo [1,5-a]pyridines studied by NMR, IR spectroscopy and molecular orbital calculations

The 6-nitro- and 8-nitro- groups in the tetrazolo[1,5-a]pyridine molecule exhibit completely different influences on the tetrazole–azide equilibrium. Introduction of the methyl-, nitro-, azido groups or a bromine atom in positions 5, 6, 7 or 8 of the nitrotetrazolopyridine produce changes in the equilibrium constants. Based on the IR spectra taken in the solid state, the tetrazole structure was assigned for almost all the compounds studied. Only one of them, 2,6-diazido-3-nitropyridine, exists in the diazido-form in the solid. The ¹H, ¹³C, ¹⁵N, and ¹⁷O NMR spectral parameters (coupling constants, chemical shifts) as well as ab initio molecular orbital calculations were used to describe the tetrazole–azide tautomerism in solutions. The differences in the NMR parameters between the neutral compound (6,8-dinitrotetrazolo[1,5-a]pyridine) and its σ-adducts are also included as data for distinguishing between both molecules.     

Studies on adducts of rhodium(II) tetraacetate and rhodium(II) tetratrifluoroacetate with some amines in CDCl3 solution using H, C and N NMR

¹H, ¹³C and ¹⁵N NMR spectroscopy has been applied for investigation of amine adducts with rhodium(II) tetraacetate dimer and rhodium(II) tetratrifluoroacetate dimer in CDCl₃ solution. Subsequent formation of two adducts, 1:1 and 2:1, was proved by NMR and VIS titration experiments, and by NMR measurements at reduced temperatures, from 233 to 273 K. The adduct formation shift, defined as Δδ=δ_adduct−δ_ligand and characterizing complexation reaction, varies from ca. 0 to +1.6 ppm for ¹H, from ca. −10 to +6 ppm for ¹³C and from −4.4 to −39 ppm for ¹⁵N NMR. Formation of N–Rh bond slows the inversiof on the nitrogen atom and generates, in the case of N-methyl-(1-phenylethyl)-amine, a nitrogenous chiral center in the molecule. VIS spectra of amine-dirhodium salt mixture contain two bands in the 532–597 nm spectral range, assigned to 1:1- and 2:1-adducts.     

Molecular motion and phase transition in perovskite-type (CH3)nNH4−nSnCl3 (n=1–4) studied by proton NMR spin–lattice relaxation

Powder X-ray diffraction, ¹¹⁹Sn NMR spectra, and ¹H NMR spin–lattice relaxation times, T₁, were measured for (CH₃)_nNH_4−nSnCl₃ (n=1–4). From the Rietveld analysis, it is shown that all four compounds crystallize into deformed perovskite-type structures at room temperature. The temperature dependence of ¹H T₁ was analyzed in terms of the CH₃ reorientation and other motions of the whole cation. Except for the phase transition in CH₃NH₃SnCl₃, which is from monoclinic to rhombohedral at 331 K, ¹H T₁ was continuously changed at other phase transitions in this compound as well as in the n=2–4 compounds, suggesting that the transitions are not caused by the change of the motional state of the cation but by an instability of the [SnCl₃]_nⁿ⁻ perovskite lattice.     

高分辨NMR研究金属盐对水溶性铑膦配合物分子结构的影响

用高分辨NMR研究了NaCl、NiSO₄、CuSO₄、Fe₂(SO₄)₃和Cr₂(SO₄)₃对水溶性铑膦配合物HRh(CO)(TPPTS)₃[TPPTS;P(m-C₆H₄SO₃Na)₃]分子结构的影响.³¹P(¹H)和¹HNMR谱显示,于室温下在HRh(CO)(TPPTS)₃中加入的NaCl或NiSO₄对配合物的特征³¹P(¹H)和¹HNMR谱峰无明显影响;当加入CuSO₄后,配合物的Rh-H质子峰强度弱化明显,进而消失,且原配合物的特征磷谱峰强度减弱,新生成的磷物种谱峰逐渐成为磷谱的主要物种.当加入Fe₂(SO₄)₃或Cr₂(SO₄)₃后,三价金属离子的强顺磁性使NMR灵敏度下降,谱峰宽化,该2种盐均易与水溶性铑膦配合物产生强烈的相互作用,易使配合物特征谱峰消失.实验结果表明,上述金属盐对配合物结构破坏性大小的顺序为;Fe₂(SO₄)₃>Cr₂(SO₄)₃>CuSO₄》NiSO₄～NaCl.     

B环对位取代异黄酮化合物的核磁共振研究

对14个合成的B环对位取代异黄酮化合物核磁共振氢谱进行了研究.利用超导核磁共振归属了B环无取代异黄酮质子的化学位移,根据取代基化学位移的变化影响规律考察了取代基对分子的影响方式.研究结果表明,2'(6'),3'(5')位质子共振迁移分别与取代基参数σ_p和S_o线性相关,说明4'位取代基主要通过电子效应影响其间位质子,其磁各向异性仅影响邻位质子,该取代基对A环质子影响不大,而对C环尤其是对2-H影响较明显.     

部分还原二氧化钛的NMR和EPR研究

Partially reduced TiO₂ nanomaterials have attracted significant interest because of their visible-light activity for catalysis and photodegradation. Herein, we prepared a partially reduced anatase TiO₂ (Re-A-TiO₂) nanoparticle material using a fast combustion method, demonstrating good activity toward decomposing methyl orange under visible light irradiation. The surface structure of the prepared material, after being surface-selectively ¹⁷O-labeled with H₂¹⁷O (¹⁷O-enriched water), was studied via ¹⁷O and ¹H solid-state magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy and electron paramagnetic resonance (EPR) spectroscopy, and the obtained results were compared to those of non-reduced anatase TiO₂ (A-TiO₂). The EPR results showed that the concentrations of paramagnetic species (i.e., oxygen vacancies (OV) and Ti³⁺) in Re-A-TiO₂ were much higher than that in A-TiO₂, while the former was associated with a higher OV/Ti³⁺ ratio. The intensities of the EPR signals were significantly affected by the adsorbed water, and this phenomenon was explored in combination with ¹H NMR spectroscopy. The ¹H species on Re-A-TiO₂ appeared at larger chemical shifts, denoting the increased acidity of the sample, and these ¹H species on Re-A-TiO₂ were more difficult to remove than those on A-TiO₂. On the other hand, different features were observed for the signals arising from the two-coordinated oxygen atoms (μ₂-O) in ¹⁷O NMR, suggesting a typical anatase TiO₂(101) surface on A-TiO₂, but a more complex surface environment for Re-A-TiO₂. Furthermore, a larger amount of hydroxyl groups (OH) were observed on Re-A-TiO₂ compared to that on A-TiO₂, indicating a larger proportion of exposed (001) facets on Re-A-TiO₂. However, the μ₂-O signals broadened and became similar when the drying temperature was increased to 100 ℃, indicating a non-faceted anatase TiO₂ surface in such conditions. Based on the EPR and NMR results, a significant fraction of the OH species is believed to be formed from the reaction of the paramagnetic centers and adsorbed water molecules. The ¹H→¹⁷O cross polarization (CP) MAS and two-dimensional heteronuclear correlation (2D HETCOR) NMR spectra were used to verify the spatial proximity of the hydrogen and oxygen species, confirming the spectral assignments of a strongly adsorbed water and one type of surface OH species. In particular, the ¹H NMR signals at approximately 11 ppm were ascribed to the hydrogen species in the intramolecular hydrogen bond. In summary, this study investigated the paramagnetic species and surface structure of anatase TiO₂ materials by combining EPR along with ¹H and ¹⁷O solid-state NMR spectroscopy. The differences in the surface structures of Re-A-TiO₂ and A-TiO₂ should be closely related to their different properties toward the photodegradation of methyl orange.     

NMR spectra of salicylohydroxamic acid in DMSO-d6 solution: a DFT study

The ¹H, ¹³C and ¹H, ¹³C COSY NMR spectra of salicylohydroxamic acid (sha) were measured in DMSO-d₆ solution. The B3LYP GIAO method with the 6-311++G(d,p) basis set was chosen to reproduce the experimental spectra. All possible zusammen and entgegen conformers of monomeric sha were computed. After geometry optimisation (B3LYP/6-311++G(d,p)) only nine independent models of the molecule were shown to be stable. Additionally, the NMR chemical shifts of the Onsager model of the most stable monomer were calculated. The computed chemical shifts for the labile protons for all aforementioned geometries meaningfully underestimated experimental results suggesting the existence of the H-bonded structure of sha in DMSO solution. The most probable two dimeric structures along with two solvent-bounded aggregates were subsequently calculated at the same level of theory. The best agreement was obtained for sha H-bonded with two DMSO molecules (confirmed by the absence of concentration effect). The relative error not exceeding 10 and 4% for chemical shifts in ¹H and ¹³C NMR spectra of sha–(DMSO)₂, respectively, showed that the applied method with the B3LYP/6-311++G(d,p) basis set was efficient to predict the NMR shifts of a compound with strong H-bonds. Thus, this allows to assign properly NMR resonances to specific structure formed in DMSO solution.     

An unexpected allomer of chlorophyll: 13(S)-hydroxy-10-methoxychlorophyll b

The allomerization of chlorophyll b in methanol produced 13²(S)-hydroxy-10-methoxychlorophyll b in a yield of ca. 8%. The formation of this allomer was totally unexpected, as 10-substituted chlorophylls have never been reported before. The structure of the new chlorophyll b derivative was determined on the basis of UV/Vis, FAB-MS, ¹H NMR and 2D ROESY NMR spectra. This letter focuses on the NMR analysis.     

酸碱存在下水溶性铑膦配合物的NMR表征及氢甲酰化性能研究

31P(¹H)NMR和¹HNMR研究表明,当NaOH加入到水溶性铑膦配合物HRh(CO)·(TPPTS)₃[TPPTS:P(m-C₆H₄SO₃Na)₃]后,可观察到有少量的OTPPTS[OTPPTS:O=P(m-C₆H₄SO₃Na)₃]出现,但配合物的特征谱峰即使在高浓度的NaOH存在下也基本保持不变,表明NaOH对配合物分子结构的影响较小;当吡啶加入到HRh(CO)(TPPTS)₃中,³¹P(¹H)NMR谱图中出现游离配体TPPTS的³¹P谱峰及若干结构未知的新水溶性配合物的³¹P谱峰,表明吡啶分子将与配合物分子中的配体TPPTS发生配体交换反应.在HRh(CO)(TPPTS)₃中分别加入一定量的HCl,HNO₃,H₂SO₄和H₃PO₄等无机酸时,随着酸量的增加,配合物的³¹P物种含量逐渐下降,而OTPPTS量明显上升,直至配合物³¹P物种完全消失;高浓度乙酸对配合物结构的影响与上述无机酸类似.HRh(CO)(TPPTS)₃的1-己烯氢甲酰化催化反应结果表明,碱存在下可获得较高的正异构醛比值,但催化活性降低;酸存在下所得产物正异构醛比值相对较低且呈淡黄色.