scholarly journals Protolysis and Complex Formation of Organophosphorus Compounds—Characterization by NMR-Controlled Titrations

Molecules ◽  
2019 ◽  
Vol 24 (18) ◽  
pp. 3238 ◽  
Author(s):  
Hägele
Keyword(s):  
Dissociation Constants ◽  
Organophosphorus Compounds ◽  
Chemical Shifts ◽  
2D Nmr ◽  
Coupling Constants ◽  
Phosphonic Acids ◽  
Specific Chemical ◽  
Hyphenated Technique ◽  
Aminophosphonic Acids ◽  
2D Nmr Spectra

Phosphonic acids, aminophosphonic acids, and phosphonocarboxylic acids are characterized by an advanced hyphenated technique, combining potentiometric titration with NMR spectroscopy. Automated measurements involving 13C, 19F and 31P nuclei lead to “pseudo 2D NMR” spectra, where chemical shifts or coupling constants are correlated with analytical parameters. Dissociation constants, stability constants, dynamic and specific chemical shifts are determined. Macroscopic and microscopic dissociation equilibria are discussed.

NMR-spektroskopische Untersuchung des Problems der Valenzisomerie zwischen 1,2-Dithiin und (Z)-But-2-en-1,4-dithion / NMR Spectroscopic Investigation Concerning the Problem of Valence Isomerism between 1,2-Dithiine and (Z)-But-2-ene-1,4-dithione

1988 ◽  
Vol 43 (5) ◽  
pp. 605-610 ◽  
Author(s):  
Reiner Radeglia ◽  
Helmut Poleschner ◽  
Werner Schroth
Keyword(s):  
Nmr Spectra ◽  
Chemical Shifts ◽  
2D Nmr ◽  
Ring Structure ◽  
Coupling Constants ◽  
Nmr Parameters ◽  
Spectrum Simulation ◽  
2D Nmr Spectra ◽  
Transoid Conformation ◽  
C Nmr

3,6-Diaryl-1,2-dithiines and their precursors, (Z,Z)-1,4-bis(organylthio)-buta-1,3-dienes, are investigated by 1H and 13C NMR spectroscopy. The chemical shifts and coupling constants, which are relevant to the investigated problem, are determined and assigned, respectively, by different techniques (shift increments, spectrum simulation, heteronuclear 2D J-resolved and heteronuclear shift correlated 2D NMR spectra, anomalous off-resonance splittings and selective decoupling experiments). The NMR parameters are discussed in relation to the molecular structure. The 13C shift values prove the ring structure of 1,2-dithiines and exclude existence of the valence isomer (Z)-but-2-ene-1,4-dithione (absence of thiocarbonyl resonances). The vicinal 1H,1H coupling constants of the C4 unit of the investigated compounds verify (1) the (Z,Z) configuration of the organylthio groups in 1,4 position of butadiene, (2) the s-transoid conformation of acyclic butadienes and (3) the forced s-cis structure in the cyclic 1,2-dithiines.

scholarly journals 1H and13C NMR spectroscopic studies of half-esters from monohydrolysis of dialkyl bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylates

2004 ◽  
Vol 18 (3) ◽  
pp. 469-483
Author(s):  
Yoshikazu Hiraga ◽  
Satomi Niwayama
Keyword(s):  
Nmr Spectra ◽  
Chemical Shifts ◽  
2D Nmr ◽  
Spectroscopic Studies ◽  
Carboxyl Group ◽  
1H And13c Nmr ◽  
Nmr Chemical Shifts ◽  
2D Nmr Spectra ◽  
Spectral Assignment ◽  
C Nmr

The structures of the half-esters from the monohydrolysis of (exo,exo)-, (endo,endo)-, and (endo,exo)-dialkyl bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylates were determined by1H and13C NMR as well as 2D NMR spectra, and the complete spectral assignment has been made. After conversion of one of the carboalkoxy groups to a carboxyl group, different tendencies were observed for the differences in1H and13C NMR chemical shifts between half-esters and the corresponding diesters.

scholarly journals New Alkaloid from Aspidosperma Polyneuron Roots

2008 ◽  
Vol 3 (2) ◽  
pp. 1934578X0800300
Author(s):  
Tatiane Alves dos Santos ◽  
Dalva Trevisan Ferreira ◽  
Jurandir Pereira Pinto ◽  
Milton Faccione ◽  
Raimundo Braz-Filho
Keyword(s):  
Nmr Spectra ◽  
Chemical Shifts ◽  
Preliminary Investigation ◽  
Ethanolic Extract ◽  
2D Nmr ◽  
Artemia Salina ◽  
Mass Spectrometric ◽  
Mass Spectrometric Data ◽  
Spectrometric Data ◽  
2D Nmr Spectra

The roots of Aspidosperma polyneuron, family Apocynaceae, were subjected to chemical and biological investigations. From an ethanolic extract of the roots, the new alkaloid 2,7-dihydroxyquebrachamine (1) was isolated. The structure was established mainly from 1D and 2D NMR spectroscopic and mass spectrometric data. The 1D and 2D NMR spectra were also used to assign all the 1H and 13C chemical shifts of this alkaloid. Artemia salina was used for a preliminary investigation of biological activity.

scholarly journals Duplicate detection of 2D-NMR Spectra

2007 ◽  
Vol 4 (1) ◽  
pp. 64-80 ◽  
Author(s):  
Alexander Hinneburg ◽  
Björn Egert ◽  
Andrea Porzel
Keyword(s):  
Measurement Errors ◽  
Nmr Spectra ◽  
Structural Information ◽  
Chemical Shifts ◽  
Dimensional Space ◽  
Real Data ◽  
2D Nmr ◽  
2D Nmr Spectra ◽  
Definition Of ◽  
Short Time

Abstract 2D-Nuclear magnetic resonance (NMR) spectra are used in the (structural) analysis of small molecules. In contrast to 1D-NMR spectra, 2D-NMR spectra correlate the chemical shifts of 1H and 13C at the same time. A spectrum consists of several peaks in a two--dimensional space. The most important information of a peak is the location of its center, which captures the bonding relationships of hydrogen and carbon atoms. A spectrum contains much information about the chemical structure of a product, but in most cases the structure cannot be read off in a simple and straightforward manner. Structure elucidation involves a considerable amount (manual) efforts. Using high-field NMR spectrometers, many 2D-NMR spectra can be recorded in short time. So the common situation is that a lab or company has a repository of 2D-NMR spectra, partially annotated with the structural information. For the remaining spectra the structure in unknown. In case two research labs are collaborating, the repositories will be merged and annotations shared. We reduce that problem to the task of finding duplicates in a given set of 2D-NMR spectra. Therefore, we propose a simple but robust definition of 2D-NMR duplicates, which allows for small measurement errors. We give a quadratic algorithm for the problem, which can be implemented in SQL. Further, we analyze a more abstract class of heuristics, which are based on selecting particular peaks. Such a heuristic works as a filter step on the pairs of possible duplicates and allows false positives. We compare all methods with respect to their run time. Finally we discuss the effectiveness of the duplicate definition on real data.

scholarly journals γ-PNA PREORGANIZATION: SYNTHESIS OF MODEL DIMER AND ITS STRUCTURE STUDY BY 2D NMR SPECTROSCOPY

2017 ◽  
Vol 12 (2) ◽  
pp. 62-71
Author(s):  
A. V. Dezhenkov ◽  
D. A. Cheshkov ◽  
I. A. Prokhorov ◽  
A. I. Lutik ◽  
Yu. G. Kirillova
Keyword(s):  
Nmr Spectroscopy ◽  
Chemical Shifts ◽  
2D Nmr ◽  
Structure Study ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Double Quantum ◽  
2D Nmr Spectroscopy ◽  
The Right ◽  
Spin Spin Coupling

The synthesis of a dimer consisting of γ-thymine chiral monomer based on L-Ala and thymine aeg-PNA monomer (synthesized from deuterated glycine), in which the methylene protons of the pseudopeptide residue were exchanged with deuterium atoms, was described. The deuterated monomer was introduced into acylation reaction by means of a mixed anhydride procedure with γ-PNA chiral monomer trifluoroacetate based on L-Ala. The latter was obtained from the fully protected thymine monomer by the reaction with trifluoroacetic acid. The structure and purity of the target monomer were confirmed by NMR-spectroscopy, and the elemental composition was estimated by quantitative elemental analysis. The double quantum filtered COSY-NMR-spectroscopy (DQF-COSY) method was used to determine the methylene signals of the dimer chiral fragment. With the use of the spectrum analysis, the chemical shifts and calculated spin-spin coupling constants of the protons from the dimer chiral part were found. Given that Karplus equation associates the value of the dihedral angle between the vicinal protons with their spin-spin coupling constant, it was concluded that the chiral fragment is in the right-helix conformation for all the dimer rotamers.

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