Über Chalkogenolate. 103. Reaktion von Guanidin mit Kohlenstoffdisulfid

On Chalcogenolates. 103. Reaction of Guanidine with Carbon Disulfide The reaction between guanidine and carbon disulfide in cold aqueous acetone leads to guanidinium guanidinodithioformate. In heat the reaction gives guanidinium trithiocarbonate and the guanidinium salt of 4-imino-2,6-dithio-1,3,5-thiadiazine. In ethanolic solution guanidine reacts with carbon disulfide to form guanidinium ethyl xanthate. The prepared compounds have been characterized with chemical methods as well as by means of electron absorption spectra, i.r. spectra, n.m.r. spectra, and mass spectra.     

气相色谱/离子阱质谱中组分图谱提取的主成分分析方法

由于离子阱质谱中容易发生分子-离子反应, 致使质谱图发生改变, 影响与主要由四极质谱建立的参照图谱的匹配效果. 本文采用主成分分析方法对气相色谱/离子阱质谱中组成色谱峰的所有全扫描质谱进行提取, 提取后的质谱图能够有效克服分子-离子反应和基线干扰的影响, 应用不同的匹配算法均能很好地和参照图谱匹配, 和传统方法相比匹配度显著提高, 对目标化合物定性准确.     

Application of gas chromatography-cryocondensation-Fourier transform infrared spectroscopy and gas chromatography-mass spectrometry to the identification of gas phase reaction products from the alpha-pinene/ozone reaction

The gas phase reaction of alpha-pinene with the atmospheric oxidant ozone was investigated by using the capabilities of both gas chromatography-cryocondensation-Fourier transform infrared spectroscopy (GC-FT-IR) and gas chromatography-mass spectrometry (GC-MS), for the identification of the reaction products formed. The reaction was carried out in a flow reaction chamber from where the compounds were sampled on Tenax-containing adsorption cartridges. The reaction mixture was injected onto the column after thermodesorption and analyzed using both GC-IR and GC-MS. Twenty compounds could be detected, including the reactant alpha-pinene and it's impurities tricyclene and camphene. Eleven compounds were identified by spectra comparison with either reference data or spectra obtained from commercial standards. Four compounds were tentatively identified from their IR and MS spectra, while from the remaining two compounds the nature of basic functional groups could be established.     

尾式甘氨酸四苯基卟啉锌与吡啶类化合物轴配反应光谱和热力学

取代四苯基卟啉锌配合物与咪唑类和吡啶类等含氮化合物轴向配位反应的研究在模拟生物体中锌酶的作用机理方面具有重要意义。在现有的文献中 ,人们的研究主要集中在四苯基卟啉的苯环上连有如卤素、甲氧基、甲基等较小取代基的卟啉锌上[1～3] ,对于结构不对称且苯环上连有氨基酸的四苯基卟啉锌与含氮化合物轴向配位反应的研究尚不多见。有关尾式氨基酸四苯基卟啉锌配合物的合成和性质我们进行过较系统的研究[4～6] 。本文以 5 ( 4 甘氨酸丁氧苯基 ) 1 0 ,1 5 ,2 0 三苯基卟啉锌 (ＺｎＰ)为锌酶的模型化合物 ,用热力学方法研究了它与吡啶 (…     

Analysis of the CO2 and NH3 reaction in an aqueous solution by 2D IR COS: formation of bicarbonate and carbamate

The two-dimensional (2D) infrared correlation spectra obtained from the reaction time- and concentration-dependent IR spectra elucidates the reaction of CO2 and NH3 in an aqueous solution for CO2 absorption. In the synchronous 2D correlation spectra, the interrelation of the proton with carbamate and bicarbonate indicates that the pH level affected the formation reactions of the two products. Furthermore, the interrelation of carbamate with bicarbonate confirmed the conversion of carbamate into bicarbonate with the release of protons (or the decrease of the pH). From the experimental results including the asynchronous 2D correlation spectra, the reaction of the CO2 and aqueous ammonia proceeded through the following steps: formation of carbamate, formation of bicarbonate, release of protons, and conversion of carbamate into bicarbonate. The analysis of the formation of carbamate and bicarbonate by 2D infrared correlation spectroscopy provides useful information on the reaction mechanism of CO2 and NH3 in aqueous solutions.     

Application of a new method for simultaneous phase and baseline correction of NMR signals (SINC)

Recently, we presented a new approach for simultaneous phase and baseline correction of nuclear magnetic resonance (NMR) signals (SINC) that is based on multiobjective optimization. The algorithm can automatically correct large sets of NMR spectra, which are commonly acquired when reactions and processes are monitored with NMR spectroscopy. The aim of the algorithm is to provide spectra that can be evaluated quantitatively, for example, to calculate the composition of a mixture or the extent of reaction. In this work, the SINC algorithm is tested in three different studies. In an in-house comparison study, spectra of different mixtures were corrected both with the SINC method and manually by different experienced users. The study shows that the results of the different users vary significantly and that their average uncertainty of the composition measurement is larger than the uncertainty obtained when the spectra are corrected with the SINC method. By means of a dilution study, we demonstrate that the SINC method is also applicable for the correction of spectra with low signal-to-noise ratio. Furthermore, a large set of NMR spectra that was acquired to follow a reaction was corrected with the SINC method. Even in this system, where the areas of the peaks and their chemical shifts changed during the course of reaction, the SINC method corrected the spectra robustly. The results show that this method is especially suited to correct large sets of NMR spectra and it is thus an important contribution for the automation of the evaluation of NMR spectra.     

Phthalocyanines and related compounds: XLVI. [4+2]-cycloaddition of tetraazaporphine to dienes of the cyclopentadiene series

The [4+2]-cycloaddition reaction of unsubstituted tetraazaporphine as the dienophile with a series of dienes of the cyclopentadiene series gave novel norbornene-condensed tetraazachlorins, tetraazabacteriochlorins, and tetraazaisobacteriochlorins. It was shown that, depending on the type of the diene, the reagent ratio, reaction time, and temperature mono-or bis-adducts are formed. The compounds obtained were characterized by the elemental analyses, electronic absorption spectra, ¹H NMR spectra, and mass spectra.     

锌卟啉轴向配合物的光谱特性及配位二聚体分子内的能量传递

通过轴向配位作用构造了ZnTPP-H₂(m-py)TPP卟啉二元体系,研究了配位二聚体的可见吸收光谱和荧光发射光谱特性,考察了二聚体分子内的能量传递过程,观察到能量从激发态ZnTPP^*流向H₂(m-py)TPP。作为对比,研究了ZnTPP-py体系的可见吸收光谱和荧光发射光谱。轴向配位的吡啶引起了ZnTPP荧光光谱明显红移,没有分子内的能量转移过程发生。用吸收光谱和荧光光谱方法计算了加合反应的平衡常数,得到了基本一致的结果。     

金属氯化醇盐的红外光谱分析

金属氯化醇盐作为一种溶胶．凝胶法新型前驱体,其分子结构较为复杂,但关于它们结构的红外光谱分析却很少。为此,文章分别对四氯化钛和三氯化铝与乙醇、异丙醇及正丁醇的反应产物——金属氯化醇盐进行了红外光谱测试分析。结果发现,由于四氯化钛中钛的反应活性参数Rn较小,同时三氯化铝中离子键较少,因此,它们与醇之间只发生了部分亲核取代反应,导致产物中残余一定量的Ti-Cl和Al-Cl键合,即反应产物为铝、钛氯化醇盐,这样造成铝氯化醇盐的红外图谱中存在Al-Cl键合振动吸收峰,而钛氯化醇盐中C-O-Ti键合的C-O伸缩振动吸收峰峰位也明显有别于纯的金属钛醇盐。     

Improvements in ion-trap chemical-ionization performance.

Ion-trap chemical-ionization performance has been improved by application of a modified scan function for the rejection of the undesired electron-ionization-like (EI-like) ions formed at the beginning of the reaction ionization period. The net effect of this software modification to the automatic reaction control is to produce chemical ionization (CI) spectra that are no longer adulterated with concentration-dependent EI-like ions. Under such improved conditions, CI spectra from an ion trap can now be directly compared with CI spectra produced on conventional quadrupole and magnet-scanning instruments.     

高锰酸钾-鲁米诺反应体系中碱土金属离子Mg2+,Ca2+,Sr2+,Ba2+化学发光行为研究

将被认为没有化学发光活性的第二主族(碱土金属)离子Mg^2 ,Ca^2 ,Sr^2 ,Ba^2 溶液注入到已充分反应的高锰酸钾与鲁米诺混合液中时,又发生了新的化学发光反应,并检测到强的化学发光信号．在对有关反应的动力学性质、化学发光光谱、紫外可见光谱及其它一系列实验研究的基础上,提出了可能的化学发光反应机理．同时,优化了反应条件,评价了这一反应用于Mg^2 ,Ca^2 ,Sr^2 ,Ba^2 分析的可行性．     

Molecular Dynamics of Excited State Intramolecular Charge Transfer in Solution by Coherent Nuclear Wave Packets

Revealing a proper reaction coordinate in a chemical reaction is the key step towards elucidation of the molecular reaction dynamics. In this report, we investigated the dynamics of intramolecular charge transfer (ICT) of 8-aminopyrene-1,3,6-trisulfonic acid (APTS) occurring in the excited state by time-resolved fluorescence (TF) and TF spectra. Accurate reaction rates and rate-dependent nuclear wave packets in the product state allow detailed investigation of the molecular reaction dynamics. The ICT rate is solvent dependent: (34 fs)⁻¹, (87 fs)⁻¹, and (∞)⁻¹ in water, formamide, and dimethylformamide, respectively. By recording spectra of the nuclear wave packets for different reaction rates, chemical species responsible for the emission spectra can be positively identified. The origin of the wave packets can be deduced from the amplitude change of the wave packets at different reaction rates, and the vibrational modes that are associated with the reaction coordinate could be identified. Theoretical calculations of the vibrational reorganization energies reproduce the experimental spectrum of the nuclear wave packets and corroborate the conclusions.     

Combination of Single Bead FTIR and Chemometrics in Combinatorial Chemistry: Application of the Multivariate Calibration Method in Monitoring Solid-Phase Organic Synthesis

The single bead FTIR method has been used in quantitative analyses of solid-phase organic synthesis (SPOS) such as the determination of reaction kinetics and conversion yield. These studies rely on data analysis methods to extract quantitative information from IR spectra. However, the IR spectrum of a solid-phase sample contains vibrational bands from the starting material, product, and the polymer support itself. The coexistence of multiple chemical components causes severe spectral overlaps and sometimes makes quantitative analysis extremely difficult. In some cases, it is impossible to extract qualitative and quantitative information from overlapped IR spectra. In this paper, we use partial least squares (PLS), a chemometrics method, to achieve qualitative and quantitative analysis of samples that generate severely overlapped IR spectra. The primary loading factor obtained from a PLS calculation only displays those spectral features that have undergone changes during a SPOS reaction. Disappearing and emerging organic functional groups generate negative and positive signals, respectively, in the primary loading factor, thus allowing qualitative analysis of the reaction with improved precision. The scores of the primary loading factors of spectra taken at various times during a reaction provide quantitative information allowing the study of the reaction kinetics directly on solid support. On the basis of the analysis of three diverse SPOS reactions, the PLS method has demonstrated the unique capability of extracting quantitative and qualitative information from the overlapped IR spectra. It is a powerful data analysis tool for the monitoring of SPOS reactions in combinatorial chemistry.     

碳酸二甲酯法制备1,5-萘二氨基甲酸甲酯中间产物的结构表征

研究发现,由碳酸二甲酯与1,5-萘二胺合成1,5-萘二氨基甲酸甲酯的反应是一个经过中间产物的串联反应。关于这个中间产物,在目前现有的各种文献中未见报道。本文利用萃取、结晶等分离手段提纯出了该中间产物,并通过质谱、元素分析、红外光谱以及核磁共振谱等分析方法对其组成和结构进行了测定,结果表明该中间产物的分子量为216,组成为C12H12N2O2,结构为5-氨基-萘基-1-氨基甲酸甲酯。     

高碘酸钾-鲁米诺体系中一些后化学发光反应的研究

研究了葡醛内酯、盐酸美司坦和重酒石酸去甲肾上腺素等10种物质在高碘酸钾-鲁米诺体系中的后化学发光现象、后化学发光反应的动力学、化学发光光谱、荧光光谱以及其它相关性质, 提出了其可能的发光机理; 在优化的分析条件下建立了这10种物质的后化学发光分析方法, 初步构建了高碘酸钾-鲁米诺后化学发光分析体系.     

固体^1^3C NMR研究呋喃醇和呋喃醇与三-(2-羟乙基)-异氰酸尿酯缩聚磺化反应

用固体^1^3C NMR研究了呋喃醇(FA)和FA与三-(2-羟乙基)-异氰酸尿酯(THEIC)缩聚磺化反应及其产物结构, 考察了2-甲基呋喃封端的FA线型齐聚物与甲醛水溶液在相转移催化剂(C~4H~9)~4N^+I^-和与大量硫酸作用下的反应特点, 探讨了主要参数对反应的影响。阐明了缩聚交联磺化反应的规律, 确定了产物的结构。     

Spectroscopic and quantitative analysis of spiroorthoester synthesis by two-dimensional correlation and multivariate curve resolution methods of NIR data

The spiroorthoester synthesis includes several competitives reactions. A way of determining the reactions that are taking place and their sequential order, is presented. The reaction between the phenylglycidylether and gamma-butyrolactone to obtain a spiroorthoester has been monitored by near-infrared spectroscopy (NIR). In addition to the formation of the corresponding spiroorthoester, some parallel processes can occur. By means of two-dimensional correlation analysis, only one reaction is postulated, the one corresponding to the spiroorthoester formation. This was confirmed by recording the NMR spectra of the final product. Applying multivariate curve resolution-alternating least squares (MCR-ALS) to the NIR spectra obtained during the reaction, it has been possible to obtain the concentration values of the species involved in the reaction. The recovered spectra were compared with the experimentally recorded spectra for the reagents (phenylglycidylether, gamma-butyrolactone) and the final product (spiroorthoester) and the correlation coefficients were, in all cases, higher than 0.990. The maximum and minimum limits associated with the ALS solutions were calculated, making it possible to limit to a considerable extent the ambiguity that is characteristic of these curve resolution methods.     

Density functional based vibrational study of conformational isomers: Molecular rearrangement of benzofuroxan

The molecular rearrangement of benzofuroxan was studied by comparing calculated and experimental IR spectra, the latter taken before and during the reaction. All calculations were performed at the B3-LYP/6-31G(d) density functional level with a further refinement of the computed force constants done by applying the scaled quantum mechanical force field (SQM) technique. Complete assignments for the IR spectra of benzofuroxan and nitrosobenzene are given. The agreement between computed and experimental spectra is excellent, but in benzofuroxan these spectra are very different from previously calculated data. The conformation of the ortho-dinitrosobenzene intermediate of this tautomeric reaction was identified by modeling a composite IR spectrum of four possible components. It shows good agreement with an experimental spectrum that was obtained after photolysing benzofuroxan in Xe matrix. Knowing the conformation of the intermediate provides insight into the reaction mechanism and allows inferences for the thermal reaction, which could not be clarified conclusively by energetic considerations only. © 1997 by John Wiley & Sons, Inc. J Comput Chem 18: 489–500, 1997     

Fluorescein–formaldehyde oligomeric pH indicator: Facile synthesis,characterization, and potential application

A kind of fluorescent oligomeric pH indicator (fluorescein–formaldehyde product) was synthesized by the reaction of fluorescein with formaldehyde under alkaline conditions by a one‐pot method. The synthesized product was fully characterized with Fourier transform infrared, ¹H NMR, ultraviolet–visible spectra, luminescence spectra, and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectra. The results indicated that the reaction was a typical phenol–formaldehyde reaction and that the fluorescein–formaldehyde product contained dimer, trimer, tetramer, and even a little octamer. Visible spectra and luminescence spectra showed that the fluorescein–formaldehyde product could still provide pH sensitivity similar to that of fluorescein. In addition, the oligomeric pH indicator immobilized poly(vinyl alcohol) membranes could be easily fabricated and achieved better long‐term stability and fast equilibrium response. Thus, they are promising transparent membranes for optical pH sensors of a wide pH range (0.0–10.0) based on absorption and fluorescence. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3447–3453, 2005     

Configuration of spheroidene in the photosynthetic reaction center of Rhodobacter sphaeroides : a comparison of wild-type and reconstituted R26

We compare the resonance Raman spectra acquired at two excitation wavelengths, 496.5 and 514.5 nm, of spheroidene in the wild-type reaction center of Rhodobacter sphaeroides and reconstituted into the reaction center of the Rhodobacter sphaeroides mutant R26. Our earlier work showed that the reconstituted R26 reaction center holds spheroidene in two configurations: 15,15'-cis and another configuration. Here we show that in the wild-type reaction center only 15,15'-cis spheroidene is present. In the resonance Raman spectra of the reconstituted R26 reaction centers, a transition is identified that arises exclusively from the second configuration. According to density-functional-theory calculations, this transition is specific for the 13,14-cis configuration.