Preparation and nuclear magnetic resonance characterization of N-bonded complexes of platinum(II) with phosphorus-nitrogen rings containing three-coordinate chalcogens: X-ray structure of [PtCl2(PEt3)]2(Ph4P2N4Se2Et2)

1993 ◽  
Vol 71 (11) ◽  
pp. 1821-1827 ◽  
Author(s):  
Tristram Chivers ◽  
Daniel D. Doxsee ◽  
Robert W. Hilts ◽  
Masood Parvez
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Nmr Spectroscopy ◽  
Magnetic Resonance ◽  
Nitrogen Atom ◽  
Membered Ring ◽  
Monoclinic Space Group ◽  
Hydrogen Atoms ◽  
X Ray ◽  
X Ray Crystallography

The reaction of 1,5-Ph4P2N4S2Ph2 with [PtCl2CPEt3)]2 in chloroform at 60 °C produces the 1:1 adduct trans-PtCl2(PEt3)(Ph4P2N4S2Ph2) in which the platinum is attached to a nitrogen atom on the basis of 31P nmr spectroscopy. By contrast, the corresponding reactions of 1,5-Ph4P2N4Se2R2 (R = Me, Et, Ph) produce the 2:1 adducts [PtCl2(PEt3)]2(Ph4P2N4Se2R2) (7a, R = Me; 7b, R = Et; 7c, R = Ph) which have been characterized by 1H, 31P and 77Se nmr spectroscopy and, in the case of 7b, by X-ray crystallography. Crystals of 7b are monoclinic, space group C2/c, with a = 27.803(7) Å, b = 12.378(7) Å, c = 15.752(8) Å, β = 115.49(2)°, V = 4893(3) Å3, and Z = 4. The least-squares refinement with anisotropic thermal parameters for all non-hydrogen atoms converged at R = 0.037 and Rw = 0.022. The platinum centres in 7b are attached to distal nitrogen atoms of the disordered P2N4Se2 ring. The reaction of the six-membered ring Ph4P2N3SPh with [PtCl2(PEt3)]2 in dichloromethane at 23 °C occurs in a regiospecific manner to give the 1:1 adduct PtCl2(PEt3)(Ph4P2N3SPh) in which, on the basis of 31P nmr spectroscopy, the platinum is coordinated to a nitrogen atom between phosphorus and sulfur.

scholarly journals Absolute Configuration Reassignment of Natural Products: An Overview of the Last Decade

2021 ◽  
Author(s):  
Andrea Batista ◽  
Bianca Angrisani ◽  
Maria Emanuelle Lima ◽  
Stephanie da Silva ◽  
Vitória Schettini ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Natural Products ◽  
Magnetic Resonance ◽  
Organic Synthesis ◽  
Absolute Configuration ◽  
Biological Assays ◽  
Crucial Step ◽  
X Ray ◽  
X Ray Crystallography

The assignment of absolute configuration (AC) is a crucial step in the structural characterization of natural products, especially for those subjected to biological assays. Methods such as X-ray crystallography, stereocontrolled organic synthesis, nuclear magnetic resonance (NMR), and chiroptical spectroscopies are commonly used to determine the AC of chiral natural compounds. Even with these well-established techniques, however, unambiguous stereochemical assignments of natural products remain a challenge, resulting in an increasing number of structural misassignments being reported every year. Herein, we will present the main techniques that have been used in AC reassignments of natural products over the last 10 years, along with some selected examples. Special attention will be paid to the strengths and weaknesses of each approach. With this, we expect to provide the readers with critical information to help them to choose the appropriate methods for correct AC determinations.

DETERMINATION OF THE ABSOLUTE CONFIGURATION OF NEW PIPERIDIN-4-ONE DERIVATIVE FROM Pellacalyx saccardianus BY NOESY SPECTROSCOPY

2016 ◽  
Vol 78 (3-2) ◽  
Author(s):  
Salam Ahmed Abed ◽  
Hasnah Mohd Sirat
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Nmr Spectroscopy ◽  
Magnetic Resonance ◽  
Absolute Configuration ◽  
X Ray ◽  
X Ray Crystallography ◽  
The Absolute ◽  
Nuclear Overhauser ◽  
Nuclear Magnetic

A new alkaloid, pellacalyxin was isolated from the leaves of Pellacalyx saccardianus of Rhizophoraceae family. Pellacalyxin was analyzed using nuclear Overhauser spectroscopy (NOESY) nuclear magnetic resonance (NMR) technique to determine the absolute configuration. The analysis of absolute configuration of pellacalyxin was supported by X-ray crystallography. 1H-1H NOESY NMR spectroscopy exhibited that pellacalyxin possesses two chiral centers (3S) and (6R).

Characterization of a Polyanhydride Series by Ftir

1993 ◽  
Vol 331 ◽  
Author(s):  
Mark R. Kreitz ◽  
Kathleen J. Pekarek ◽  
Edith Mathiowitz
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Fourier Transform ◽  
Nmr Spectroscopy ◽  
Magnetic Resonance ◽  
Ftir Spectroscopy ◽  
Powder Diffraction ◽  
Sebacic Acid ◽  
X Ray ◽  
Fingerprint Region

AbstractUsing Fourier-transform infrared (FTIR) spectroscopy we have characterized a polyanhydride copolymer series composed of various ratios of the diacids 1,3-bis(p -carboxyphenoxy)propane (CPP) and sebacic acid (SA). Typical peaks corresponding to the aliphatic-aliphatic (SA-SA), aromatic-aliphatic (CPP-SA), and aromatic-aromatic (CPP-CPP) diads were found in the 1820- 1710 cm−1 wavenumber range. Further peaks corresponding to the SA-SA diads were identified in the fingerprint region at 1382, 1360, 1307, and 1286 cm−1. These peak characterizations facilitate identification of bond distribution in the CPP-SA copolymer as well as other polyanhydride copolymers, and correlate well with previously presented information obtained with nuclear magnetic resonance (NMR) spectroscopy and X-ray powder diffraction.

Direct Characterization of Kerogen by X-ray and Solid-State13C Nuclear Magnetic Resonance Methods

2007 ◽  
Vol 21 (3) ◽  
pp. 1548-1561 ◽  
Author(s):  
S. R. Kelemen ◽  
M. Afeworki ◽  
M. L. Gorbaty ◽  
M. Sansone ◽  
P. J. Kwiatek ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
X Ray ◽  
Nuclear Magnetic

The crystal structure of ethyl-Z-3-amino-2-benzoyl-2-butenoate and measurement of the barrier to E,Z-isomerization

1980 ◽  
Vol 58 (17) ◽  
pp. 1821-1828 ◽  
Author(s):  
Gary D. Fallon ◽  
Bryan M. Gatehouse ◽  
Allan Pring ◽  
Ian D. Rae ◽  
Josephine A. Weigold
Keyword(s):  
Crystal Structure ◽  
Nuclear Magnetic Resonance ◽  
Hydrogen Bond ◽  
Free Energy ◽  
Magnetic Resonance ◽  
Energy Of Activation ◽  
X Ray ◽  
X Ray Crystallography ◽  
Free Energy Of Activation ◽  
Nuclear Magnetic

Ethyl-3-amino-2-benzoyl-2-butenoate crystallizes from pentane as either the E (mp 82–84 °C) or the Z-isomer (mp 95.5–96.5 °C). The E isomer is less stable, and changes spontaneously into the Z, which bas been identified by X-ray crystallography. The structure is characterised by an N–H/ester CO hydrogen bond and a very long C2—C3 bond (1.39 Å). Nuclear magnetic resonance methods have been used to measure the rate of [Formula: see text] isomerization at several temperatures, leading to the estimate that the free energy of activation at 268 K is 56 ± 8 kJ.

Structure and nuclear magnetic resonance spectra of 6-bromo-3,3′,4′,5,7-penta-O-methylcatechin

1985 ◽  
Vol 63 (8) ◽  
pp. 2176-2180 ◽  
Author(s):  
F. W. B. Einstein ◽  
E. Kiehlmann ◽  
E. K. Wolowidnyk
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Title Compound ◽  
Bromine Atom ◽  
Heterocyclic Ring ◽  
Equatorial Orientation ◽  
X Ray ◽  
X Ray Crystallography ◽  
Nuclear Magnetic Resonance Spectra ◽  
Ring Conformations

The title compound has been synthesized by selective debromination of 6,8-dibromocatechin and indirect methylation of the resulting 6-bromocatechin via its pentaacetate. The structure of C20H23BrO6 has been determined by X-ray crystallography. The compound crystallizes in the space group P1 with a = 9.589(3) Å, b = 11.576(3) Å, c = 11.326(3) Å, α = 118.80(3)°, β = 93.23(3)°, γ = 111.44(3)°, ρc = 1.481 g cm−3, and Z = 2. Intensities were measured for 2584 independent reflections (2θ < 45°) of which 2213 were observed (I > 3.0σ(I)) and used in subsequent refinement (final R values were R = 0.0268 and Rw = 0.0344). Crystallographic and pmr data confirm the position of the bromine atom at C-6, the trans-diaxial arrangement of H-2/H-3 and the quasi-equatorial orientation of the 3,4-dimethoxyphenyl group (ring B). The two heterocyclic ring conformations are consistent with the expected flexibility of the molecule.

Crystallographic characterization of three cathinone hydrochlorides new on the NPS market: 1-(4-methylphenyl)-2-(pyrrolidin-1-yl)hexan-1-one (4-MPHP), 4-methyl-1-phenyl-2-(pyrrolidin-1-yl)pentan-1-one (α-PiHP) and 2-(methylamino)-1-(4-methylphenyl)pentan-1-one (4-MPD)

2022 ◽  
Vol 78 (1) ◽  
Author(s):  
Marcin Rojkiewicz ◽  
Piotr Kuś ◽  
Maria Książek ◽  
Joachim Kusz
Keyword(s):  
Chemical Structure ◽  
Crystallographic Data ◽  
New Psychoactive Substances ◽  
Monoclinic Space Group ◽  
Psychoactive Substances ◽  
Space Group ◽  
X Ray ◽  
X Ray Crystallography ◽  
Analytical Laboratories

Cathinones belong to a group of compounds of great interest in the new psychoactive substances (NPS) market. Constant changes to the chemical structure made by the producers of these compounds require a quick reaction from analytical laboratories in ascertaining their characteristics. In this article, three cathinone derivatives were characterized by X-ray crystallography. The investigated compounds were confirmed as: 1-[1-(4-methylphenyl)-1-oxohexan-2-yl]pyrrolidin-1-ium chloride (1, C17H26NO+·Cl−, the hydrochloride of 4-MPHP), 1-(4-methyl-1-oxo-1-phenylpentan-2-yl)pyrrolidin-1-ium chloride (2; C16H24NO+·Cl−, the hydrochloride of α-PiHP) and methyl[1-(4-methylphenyl)-1-oxopentan-2-yl]azanium chloride (3; C13H20NO+·Cl−, the hydrochloride of 4-MPD). All the salts crystallize in a monoclinic space group: 1 and 2 in P21/c, and 3 in P21/n. To the best of our knowledge, this study provides the first detailed and comprehensive crystallographic data on salts 1–3.

Characterization of Natural Organic Matter by Nuclear Magnetic Resonance Spectroscopy

1997 ◽  
Author(s):  
Jerry A. Leenheer
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Organic Matter ◽  
Nmr Spectroscopy ◽  
Magnetic Resonance ◽  
Natural Organic Matter ◽  
Major Elements ◽  
Structure Information ◽  
Abundant Element ◽  
Nuclear Magnetic

Natural organic matter (NOM) is a major intermediate in the global carbon, nitrogen, sulfur, and phosphorus cycles. NOM is also the environmental matrix that frequently controls binding, transport, degradation, and toxicity of many organic and inorganic contaminants. Despite its importance, NOM is poorly understood at the structural chemistry level because of its molecular complexity and heterogeniety. Nuclear magnetic resonance (NMR) spectroscopy is one of the most useful spectrometric methods used to investigate NOM structure because qualitative and quantitative organic structure information for certain organic elements can be generated by NMR for NOM in both the solution and solid states under nondegradative conditions. However, NMR spectroscopy is not as sensitive as infrared or ultraviolet-visible spectroscopy; it is not at present applicable to organic oxygen and sulfur, and quantification of NMR spectra is difficult under certain conditions. The purpose of this overview is to present briefly the “state of the art” of NMR characterization of NOM, and to suggest future directions for NMR research into NOM. More comprehensive texts concerning the practice of NMR spectroscopy and its application to NOM in various environments have been produced by Wilson and by Wershaw and Mikita. Carbon, hydrogen, and oxygen are the major elements of NOM; together they comprise about 90% of the mass. The minor elements that constitute the remainder are nitrogen, sulfur, phosphorus, and trace amounts of the various halogen elements. With the exception of coal, in which carbon is the most abundant element, the order of relative abundance in NOM on an atomic basis is H > C > O > N > S > P = halogens. The optimum NMR-active nuclei for these elements are 1H, 13C, 17O, 15N, 33S, 31P, and 19F. The natural abundances and receptivities of these nuclei relative to 1H are given in Table 12.1. Quadrupolar effects for 17O, 33S, and halogen elements other than 19F lead to line broadening that greatly limits resolution in NMR studies of these elements in NOM.

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