共查询到20条相似文献,搜索用时 31 毫秒
1.
Leonid B. Krivdin 《Magnetic resonance in chemistry : MRC》2020,58(1):15-30
This is the third and the last part of three closely interrelated reviews dealing with computation of 1H nuclear magnetic resonance chemical shifts and 1H–1H spin–spin coupling constants. Present review deals with the computation of these parameters in biologically active natural products, carbohydrates, and other molecules of biological origin focusing on stereochemical applications of computational 1H nuclear magnetic resonance to these objects. 相似文献
2.
Talebpour Z Ghassempour A Zendehzaban M Bijanzadeh HR Mirjalili MH 《Analytica chimica acta》2006,576(2):290-296
Trichlorfon is an organophosphorus insecticide, which is extensively being used for protection of fruit crops. Trichlorfon is a thermal labile compound, which cannot be easily determined by gas chromatography (GC) and has no suitable group for sensitive detection by high performance liquid chromatography (HPLC). In this study, a 31P nuclear magnetic resonance (31P NMR) has been described for monitoring of trichlorfon without any separation step. The quantitative works of 31P NMR spectroscopy has been performed in the presence of an internal standard (hexamethylphosphoramide). Limit of detection (LOD) for this method has been found to be 55 mg L−1, without any sample preparation, and the linear working range was 150-5500 mg L−1. Relative standard deviation (R.S.D.%) of the method for three replicates within and between days was obtained ≤9%. The average recovery efficiency was approximately 99-112%. This method was applied for monitoring trichlorfon in a commercial insecticide sample and tomato sample. 相似文献
3.
Thirty three compounds were obtained from the bulbs of Urginea maritima (Liliaceae). The compounds were identified by means of fast atom bombardment mass spectrometry (FAB-MS), nuclear magnetic resonance (1H-NMR), (13C-NMR), nuclear overhauser effects (NOE) and two dimensional (2D) NMR. Ten of them were new natural compounds. Nine were bufadienolides and only one was lignan in these compounds. 相似文献
4.
Byeong C. Jeong Hyun-Won Klm Stephen Owen R. Elaine Dick Lynne E. Macaskie 《Applied biochemistry and biotechnology》1994,47(1):21-32
Tributyl phosphate (TBP) and other alkyl phosphates represent a class of persistent organophosphorus compounds of widespread use. Biodegradation of the phosphotriesters is postulated to occur through sequential hydrolytic cleavages via the phosphodiester and monoester intermediates to alcohol and inorganic phosphate (Pi). Immobilized cells of aCitrobacter sp. liberated Pi upon challenge with TBP but the reaction was short-lived. In vitro studies with purified phosphomonoesterase (phosphatase) used31P nuclear magnetic resonance to demonstrate Pi transfer onto ethanol (phosphotransferase activity). This suggested that in vivo the onset of a futile phosphohydrolytic and transphosphorylation cycle would limit the extent of phosphate production. A mutant deficient in the transphosphorylating phosphomonoesterase showed an extended release of Pi under challenge with TBP that was not subject to the complete and premature reaction termination that precluded application of the parent strain to possible industrial processes for alkyl phosphate biodegradation. 相似文献
5.
E. R. J. Wils A. G. Hulst P. E. J. Verwiel S. H. van Krimpen A. Niederhauser 《Fresenius' Journal of Analytical Chemistry》1992,343(3):297-303
Summary As part of an international round robin verification exercise, samples were analysed from a simulated inspection, which may take place under a future Chemical Weapons Convention, of a facility producing the organophosphorus insecticide 2,2-dichloroethenyl dimethyl phosphate (Dichlorvos). The identification of an unknown potential chemical warfare agent, an octyl methylphosphonofluoridate mixture, by the combination of gas chromatography-mass spectrometry (both electron impact and chemical ionization) and nuclear magnetic resonance spectrometry (19F and 31P) is described in detail. This compound mixture was added in relatively small quantities to some of the complicated chemical industry samples. 相似文献
6.
31P nuclear magnetic resonance (NMR) spectroscopy was used to detect and quantify simultaneously a large number of phenolic compounds and the two triterpenic acids, ursolic acid and oleanolic acid, extracted from two oregano species Origanum onites and Origanum vulgare ssp. Hirtum using two different organic solvents ethanol and ethyl acetate. This analytical method is based on the derivatization of the hydroxyl and carboxyl groups of these compounds with the phosphorous reagent 2‐chloro‐4,4,5,5‐tetramethyl‐1,3,2‐dioxa phospholane and the identification of the phosphitylated compounds on the basis of the 31P chemical shifts. Unambiguous assignment of the 31P NMR chemical shifts of the dihydroxy‐ and polyhydroxy‐phenols in oregano species as well as those of the triterpenic acids was achieved upon comparison with the chemical shifts of model compounds assigned by using two‐dimensional NMR techniques. Furthermore, the integration of the appropriate signals of the hydroxyl derivatives in the corresponding 31P NMR spectra and the use of the phosphitylated cyclohexanol as an internal standard allowed the quantification of these compounds. The validity of this technique for quantitative measurements was thoroughly examined. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
7.
Ahmed Chelihi Ridha Hassaine Souad Nachat Mohammed Benabdallah Karima Bendahou Mohammed Aissaoui Merzouk Saidj Ahmed Djafri Leïla Boukenna Abdelghani Bouchama Noureddine Choukchou-Braham Nadia Taibi 《Journal of heterocyclic chemistry》2024,61(3):439-457
This current work describes the preparation of MgO-SBA-15 catalysts by ultrasonic method, and it is characterized by the different analysis techniques of XRD, BET, SEM, and IRTF. In order to find out an application for this mesoporous material, MgO/SBA-15 was used as a heterogeneous catalyst in the one-pot synthesis of pyrano[3,2-c]chromenes derivatives isolated at room temperature reaction according to green chemistry criteria. To enhance these derivatives, a spectroscopic study of molecular fluorescence properties was carried out as well as an identification analysis by nuclear magnetic resonance and FTIR was used. Furthermore, biological activity experiment is also carried out, from where the obtained test results were satisfactory for AC09 , AC05 , and AC10 compounds and they are checked after computation by molecular modeling. 相似文献
8.
Andy Hay James Aguayo Walter Stark Chung-Ho Chen Ugur Camli Lou-Sing Kan 《中国化学会会志》1989,36(2):169-176
Intact human Senses incubated at 5.5 mM (normal) and 35.5 mM glucose were examined by phosphorus-31 nuclear magnetic resonance (31P NMR) spectroscopy. Lense in 35.5 mM glucose showed an altered metabolic steady-state characterized by a lowered adenosine triphosphate/inorganic orthophosphate ratio. 31P NMR spectroscopy can be used to measure metabolic changes in the lens. This model offers an important means to study dynamic metabolism in the human lens in the setting of diabetic cataractogenesis. 相似文献
9.
A. J. de Hoog 《Magnetic resonance in chemistry : MRC》1974,6(4):233-235
Fourier transform carbon-13 nuclear magnetic resonance spectra have been obtained and interpreted for some 2-substituted tetrahydropyrans. The effects of the substituents on α, β, γ and δ-carbon atoms are discussed. Using suitable reference compounds the γ-parameter can be used for quantitative conformational analysis. 相似文献
10.
11.
12.
FB Laun 《The Journal of chemical physics》2012,137(4):044704
The multiple correlation function technique is a versatile approach for the computation of the nuclear magnetic resonance (NMR) magnetization of spins diffusing in inhomogeneous fields. The difficulties in deriving the required interaction matrices are one of the main limitations of this technique. In this work, methods to compute the interaction matrices of general magnetic field profiles from those of linear fields by basic matrix manipulations are presented. As an example, susceptibility induced magnetic field profiles that are generated by cylindrical capillaries residing in homogeneous magnetic fields are considered. 相似文献
13.
F. J. Weigert 《Journal of fluorine chemistry》1993,60(2-3):103-108
This paper presents the 19F nuclear magnetic resonance chemical shifts and couplingconstants for all saturated compounds with three carbon atoms at least one fluorineatom, one terminal hydrogen atom and all possible combinations of fluorine and chlorineatoms in the remaining six positions. 相似文献
14.
本文用BRUKER MSL-400型超导核磁共振仪,对于对位取代四苯基卟啉[H_2(p-X)TPP,X=Cl,H,CH_3,OCH_3],对位取代四苯基卟啉铁(Fe(Ⅲ)(p-X)TPPCl)及其轴向配合物([Fe(Ⅲ)(p-X)TPP(HIm)_2]~+Cl~-,([Fe(Ⅲ)(p-CH_3)TPPYm]~+Cl~-,Y=2-CH_3Im,2-C_2H_5-4-CH_3Im,n-C_3H_7NH_2,N(C_2H_5)_3)的质子核磁共振谱进行了较系统的研究,探讨了分子对称性、电子结构、顺磁效应等对~1H NMR谱的影响以及铁卟啉配合物的电子自旋离域机理。 相似文献
15.
T. A. Luther R. S. Herbst D. R. Peterman R. D. Tillotson T. G. Garn V. A. Babain I. V. Smirnov E. S. Stoyanov N. G. Antonov 《Journal of Radioanalytical and Nuclear Chemistry》2006,267(3):603-613
Summary Scientists at the Idaho National Laboratory (INL) and Khlopin Radium Institute (KRI) collaboratively developed and validated
the concept of a Universal Extraction (UNEX) process for simultaneously removing the major radionuclides (Cs, Sr, actinides,
and lanthanides) from acidic radioactive waste in a single solvent extraction process. The process chemistry is unique and
complicated, since the extractants, chlorinated cobalt dicarbollide (CCD), polyethylene glycol (PEG), and diphenyl-N,N-di-n-butylcarbamoylmethylphosphine oxide (Ph2CMPO), operatesynergistically to extract the major radionuclides.A combination of classical chemistry techniques, infrared
(IR) spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy were utilized to identify and explain the structures
formed in the organic phase with protons or metal ions. Model systems, CCD-PEG and CCD-bidentate organophosphorus compounds
were studied and possible structures of complexes, existing in the organic phase, are proposed and properties of the UNEX
extractant are discussed. 相似文献
16.
The nuclear magnetic resonance and infrared properties of two new cyclic organolead compounds are discussed. 相似文献
17.
The relativistic HALA effect has been shown to depend on the spatial deformation of the lone electron pairs of a heavy atom, as demonstrated for alkyl and alkene phosphine tellurides. It was found that HALA effect on phosphorous nuclear magnetic resonance shielding constant is strongly dependent on the spatial arrangements of light substituents on phosphorus, resulting in the deformation of the lone electron pairs of tellurium. 相似文献
18.
为寻找更为有效的抗肿瘤药物,改善汉防己甲素的抗肿瘤活性,本文以汉防己甲素为原料,经过Suzuki反应设计并合成了6个新的双苄基异喹啉类衍生物。新化合物经过质谱(MS)、核磁共振氢谱(~1H NMR)、核磁共振碳谱(~(13)C NMR)等技术手段进行了结构确证。采用细胞计数试剂盒(CCK-8)法初步评价了6个新化合物对人肺癌细胞(A549)和小鼠白血病细胞(P388)的抗肿瘤活性。结果表明,化合物均有不同程度的抗肿瘤活性,其中化合物H1、H4、H6对A549细胞的抗肿瘤活性(IC5010μmol/L)明显优于阳性对照汉防己甲素。 相似文献
19.
High-field proton nuclear magnetic resonance (1H-NMR) spectroscopy was applied to the analysis of nitroaromatics and nitramines in ammunition waste water. The 1H-chemical shifts data of a variety of reference compounds are presented. Three groundwater samples, taken near the former ammunition plant Elsnig (Saxony), were analysed by high-performance liquid chromatography (HPLC) and by proton nuclear magnetic resonance spectroscopy. The results of HPLC and NMR analyses are compared and discussed. 相似文献
20.
An overview is given on recent advances of density functional theory (DFT) as applied to the calculation of nuclear magnetic
resonance (NMR) chemical shifts and electron spin resonance (ESR) g-tensors. This is a new research area that has seen tremendous progress and success recently; we try to present some of these
developments. DFT accounts for correlation effects efficiently. Therefore, it is the only first-principle method that can
handle NMR calculations on large systems like transition-metal complexes. Relativistic effects become important for heavier
element compounds; here we show how they can be accounted for. The ESR g-tensor is related conceptually to the NMR shielding, and results of g-tensor calculations are presented. DFT has been very successful in its application to magnetic properties, for metal complexes
in particular. However, there are still certain shortcomings and limitations, e.g., in the exchange-correlation functional,
that are discussed as well.
Received: 24 October 1997 / Accepted: 19 December 1997 相似文献