scholarly journals Molecular conformational evolution mechanism during nucleation of crystals in solution

IUCrJ ◽  
2020 ◽  
Vol 7 (3) ◽  
pp. 542-556
Author(s):  
Xin Li ◽  
Na Wang ◽  
Jinyue Yang ◽  
Yunhai Huang ◽  
Xiongtao Ji ◽  
...  
Keyword(s):  
Molecular Mechanism ◽  
Molecular Conformation ◽  
Nuclear Overhauser Effect ◽  
Dynamics Simulation ◽  
Conformational Polymorphism ◽  
Spectra Analysis ◽  
H Nmr ◽  
Evolution Path ◽  
Chemical Computation ◽  
Nuclear Overhauser

Nucleation of crystals from solution is fundamental to many natural and industrial processes. In this work, the molecular mechanism of conformational polymorphism nucleation and the links between the molecular conformation in solutions and in crystals were investigated in detail by using 5-nitrofurazone as the model compound. Different polymorphs were prepared, and the conformations in solutions obtained by dissolving different polymorphs were analysed and compared. The solutions of 5-nitrofurazone were proven to contain multiple conformers through quantum chemical computation, Raman spectra analysis, 2D nuclear Overhauser effect spectroscopy spectra analysis and molecular dynamics simulation. The conformational evolution and desolvation path was illustrated according to the 1H NMR spectra of solutions with different concentrations. Finally, based on all the above analysis, the molecular conformational evolution path during nucleation of 5-nitrofurazone was illustrated. The results presented in this work shed a new light on the molecular mechanism of conformational polymorphism nucleation in solution.

Synthesis, stereochemistry, and transformations of (E)-1,2-bis(benzenesulfonyl)ethylene cycloadducts to 2-oxa substituted 1,3-dienes

1984 ◽  
Vol 62 (11) ◽  
pp. 2487-2497 ◽  
Author(s):  
Ottorino De Lucchi ◽  
Vittorio Lucchini ◽  
Moreno Zamai ◽  
Giorgio Modena ◽  
Giovanni Valle
Keyword(s):  
Nuclear Overhauser Effect ◽  
H Nmr ◽  
Overhauser Effect ◽  
Nuclear Overhauser ◽  
High Yields ◽  
Structure Assignment

The cycloaddition of (E)-1,2-bis(benzenesulfonyl)ethylene (2) to 2-acetoxy- and 2-silyloxy-1,3-cyclodienes occurs in high yields and with high steroselectivity. Structure assignment has been based largely on 1H nmr nuclear Overhauser effect (nOe) experiments on the isolated products. The cycloadducts 4a and 4b derived from the 2-oxa substituted cyclopentadienes have been further elaborated to the parent norbornenone, to the respective unsaturated sulfones 5, and to the β-hydroxy substituted sulfone 6. The vinyl sulfones 5 have also been independently synthesized via cycloaddition of benzenesulfonyl acetylene. The sulfones obtained are potentially important starting molecules for the preparation of more complex targets.

An evaluation of high resolution nuclear magnetic resonance experiments and protocols in the structure elucidation of organic molecules. I. A relatively simple system, brucine

1985 ◽  
Vol 63 (2) ◽  
pp. 483-490 ◽  
Author(s):  
Michael A. Bernstein ◽  
Laurance D. Hall
Keyword(s):  
High Resolution ◽  
Chemical Shift ◽  
Structural Information ◽  
Nuclear Overhauser Effect ◽  
Proton Spectrum ◽  
Nmr Spectrum ◽  
H Nmr ◽  
Overhauser Effect ◽  
Nuclear Overhauser ◽  
Nmr Methods

Using a combination of one-dimensional (1D) and two-dimensional (2D) high resolution nmr methods, the 1H nmr spectrum of brucine was fully assigned. The 2D J-resolved and homonuclear chemical shift correlated (COSY) experiments provided assignments without full structural information; this was obtained from nuclear Overhauser effect (nOe) enhancement experiments (1D and 2D). With the proton spectrum fully assigned, proton-bearing carbons in the 13C nmr spectrum were easily assigned using the 2D heteronuclear chemical shift correlation map (CSCM) experiment.

scholarly journals Changes in the Physicochemical Properties of Piperine/β-Cyclodextrin due to the Formation of Inclusion Complexes

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Toshinari Ezawa ◽  
Yutaka Inoue ◽  
Sujimon Tunvichien ◽  
Rina Suzuki ◽  
Ikuo Kanamoto
Keyword(s):  
Physicochemical Properties ◽  
Nuclear Overhauser Effect ◽  
Biological Activities ◽  
Black Pepper ◽  
Molar Ratio ◽  
Stoichiometric Ratio ◽  
H Nmr ◽  
Overhauser Effect ◽  
Methylene Groups ◽  
Nuclear Overhauser

Piperine (PP) is a pungent component in black pepper that possesses useful biological activities; however it is practically insoluble in water. The aim of the current study was to prepare a coground mixture (GM) of PP and β-cyclodextrin (βCD) (molar ratio of PP/βCD = 1/1) and subsequently evaluate the solubility of PP and physicochemical properties of the GM. DSC thermal behavior of the GM showed the absence of melting peak of piperine. PXRD profile of the GM exhibited halo pattern and no characteristic peaks due to PP and βCD were observed. Based on Job’s plot, the PP/βCD complex in solution had a stoichiometric ratio of 1/1. Raman spectrum of the GM revealed scattering peaks assigned for the benzene ring (C=C), the methylene groups (CH2), and ether groups (C-O-C) of PP that were broaden and shifted to lower frequencies. SEM micrographs showed that particles in the GM were agglomerated and had rough surface, unlike pure PP and pure βCD particles. At 15 min of dissolution testing, the amount dissolved of PP in the GM was dramatically increased (about 16 times) compared to that of pure PP. Moreover the interaction between PP and βCD cavity was detected by 1H-1H NMR nuclear Overhauser effect spectroscopy NMR spectroscopy.

A high-field proton magnetic resonance and nuclear Overhauser effect study of prostaglandin E2

1980 ◽  
Vol 58 (15) ◽  
pp. 1577-1583 ◽  
Author(s):  
George Kotovych ◽  
Gerdy H. M. Aarts ◽  
Glen Bigam
Keyword(s):  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Nuclear Overhauser Effect ◽  
Double Resonance ◽  
Effect Study ◽  
Prostaglandin E ◽  
Hindered Rotation ◽  
H Nmr ◽  
Proton Resonances ◽  
Nuclear Overhauser

The proton magnetic resonance (1H nmr) spectrum of prostaglandin E2 (PGE2) in CDCl3 at 400 MHz bas been completely analyzed utilizing homonuclear double resonance, inversion recovery, and nOe difference experiments. The nOe difference experiments are used to assign points of configuration, namely the H-10β and the H-10α proton resonances. A spectral analysis shows that the two protons at C-3 and the two protons at C-4 are nonequivalent, indicating a hindered rotation of the chain. This is possibly due to the hairpin conformation of PGE2 in solution.

Electronic excited states of small ring compounds. IV. Bicyclo[2.1.0]pentanes by the photocycloaddition of cyclopropenes to olefins

1977 ◽  
Vol 55 (3) ◽  
pp. 393-406 ◽  
Author(s):  
D. R. Arnold ◽  
R. M. Morchat
Keyword(s):  
Excited States ◽  
Nuclear Overhauser Effect ◽  
Dimethyl Fumarate ◽  
Small Ring ◽  
H Nmr ◽  
Ring Compounds ◽  
Overhauser Effect ◽  
Direct Irradiation ◽  
Nuclear Overhauser ◽  
Thermal Stability Of

Direct irradiation of the charge-transfer complex between the cyclopropenes 3,3-dimethyl-1,2-diphenylcyclopropene (3) and 1,2,3-triphenylcyclopropene (7), and the electron deficient olefins dimethyl fumarate (5) and maleic anhydride (11) resulted in formation of the cycloadducts 6, 12–15 which are the bicyclo[2.1.0]pentane derivatives. These products were also formed when the reaction was photosensitized by triplet–triplet transfer. The structure of the adducts rests largely upon the interpretation of 13C and 1H nmr spectra. Nuclear Overhauser effect studies were used to assign stereochemistry. The thermal stability of these new bicyclo[2.1.0]-pentane derivatives has been examined, particularly with regard to the ring-flipping process and the rearrangement to the corresponding cyclopentene derivatives.

Beiträge zur Chemie der Pyrrolpigmente, XXIII [1] Die Struktur eines Bilatrien-abc-Derivates im gelösten Zustande / On the Chemistry of Pyrrole Pigments, XXIII [1] The Structure of a Bilatriene-abc Derivative in the State of Solution

1978 ◽  
Vol 33 (8) ◽  
pp. 924-931 ◽  
Author(s):  
Heinz Falk ◽  
Karl Grubmayr ◽  
Klaus Thirring
Keyword(s):  
Nitrogen Atom ◽  
Nuclear Overhauser Effect ◽  
The State ◽  
The Other ◽  
H Nmr ◽  
Overhauser Effect ◽  
Lactim Ether ◽  
Nuclear Overhauser ◽  
Shift Technique ◽  
Single Bonds

Abstract The (Z,Z,Z)-configuration of the mono-lactim-ether of an alkyl substituted bilatriene-abc, Etiobiliverdin-IV-γ, was established for chloroform solutions. Moreover the conformation of this molecule is a helical one (syn-syn-syn) with a twist along the single bonds at the methine groups of approximately 20°. The two tautomeric lactam-forms with a proton on one or the other nitrogen atom of the pyrromethene subsystem are indistin-guishable by the methods used in this investigation: 1H NMR pattern, Lanthanide induced shift technique and Nuclear Overhauser Effect measurements.

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