journal article
LitStream Collection
Home
Abramov, Vladislav M.; Tokhtueva, Maria D.; Melekhin, Vsevolod V.; Eltsov, Oleg S.
doi: 10.1002/mrc.5475pmid: 38982634
This paper presents the first example of the formation of acetonyl tridentate CˆNˆN complexes of arylbipyridines in the reaction of chloroplatinum complexes with acetone in the presence of alkali. The chemical structure of obtained substances was established by means of 1H,13C NMR, COSY, HSQC, and HMBC techniques. The attribution of all proton and carbon signals in NMR spectra was performed using 1D and 2D NMR experiments for the synthesized acetonyl cycloplatinated complexes. A comparative analysis of the values of the C‐Pt spin‐spin coupling constants of the same order was carried out, which showed a significant difference in bond lengths and valence angles inthe cyclic fragments of the arylbipyridine ligand.
doi: 10.1002/mrc.5476pmid: 39081064
Present review focuses on the most recent advances in a liquid‐phase nuclear magnetic resonance (NMR) of the coal‐derived products—coal tar pitches, asphaltenes, and humic and fulvic acids, covering exclusively the results in the liquid‐phase NMR studies leaving apart an overwhelming amount of publications dealing with the solid‐state NMR investigations in this field (which are comprehensively reviewed elsewhere). Owing to the complexity of the coal‐derived products, their 1H and 13C NMR spectra consist of a number of overlapping signals belonging to different hydrocarbon types. Comprehensive studies of coal tar pitches, asphaltenes, and humic and fulvic acids by means of NMR over the past several decades revealed characteristic functional groups of those fractions together with spectral regions in which they resonate. Quantitative 1H and 13C NMR spectra characterize aromatic and saturated carbons spread over many structural moieties, which provides a solid guideline into molecular structure of the coal‐derived products. Nowadays, quantitative 13C NMR measurements yield information about a variety of structural parameters such as functional group distribution, aromaticity, degree of condensation of aromatic rings, and medium chain lengths together with many other more specific parameters. The structural NMR studies of coal and coal‐derived products are developing on a backdrop of a marked progress in computational NMR. At present, we are witnessing an unprecedentedly fast development of theoretical and computational methods in the field of NMR spectroscopy. Discussed in the present review are the most recent advances in the NMR studies of the processing products of peat, lignite or brown coal, anthracite or hard coal, and graphite in solution, like coal tar pitches, asphaltenes, and humic and fulvic acids.
Garba, Suleiman Abubakar; Shaari, Khozirah; Abdul Manap, Mohd Rashidi; Lee, Soo Yee; Abdulazeez, Isah; Mohd Faudzi, Siti Munirah
doi: 10.1002/mrc.5477pmid: 39189504
Mitragyna speciosa is a perennial plant native to Asia, well known for its psychoactive properties. Its major alkaloid mitragynine is known to have sedative and euphoric effects. Hence, the plant has been a subject of abuse, leading to addiction, necessitating efficient analytical methods to detect its psychoactive constituents. However, current chromatography‐based methods for detecting the alkaloids are time consuming and costly. Quantitative nuclear magnetic resonance (qNMR) spectroscopy emerges as a promising alternative due to its nondestructive nature, structural insights, and short analysis time. Hence, a rapid and precise qNMR method was developed to quantify selected major psychoactive alkaloids in various parts of M. speciosa. Mitragynine, specioliatine, and speciogynine were quantified in relation to the integral value of the ‐OCH3 groups of the alkaloids and the internal standard 1,4‐dinitrobenzene. The precision and reproducibility of the method gave a relative standard deviation (RSD) of 2%, demonstrating the reliability of the method. In addition, the method showed excellent specificity, sensitivity, high linearity range (R2 = 0.999), and limits of detection (LOD) and quantification (LOQ) values. The analysis revealed that the red‐veined M. speciosa leaves contained higher levels of mitragynine (32.34 mg/g), specioliatine (16.84 mg/g) and speciogynine (7.69 mg/g) compared to the green‐veined leaves, stem bark, or fruits.
Showing 1 to 5 of 5 Articles