Two-dimensional COSY Research Articles

Facile identification of fluorosurfactant category in aqueous film-forming foam concentrates via optimized 19F NMR

Aqueous film-forming foams (AFFFs) are the primary source of toxic perfluoroalkyl and polyfluoroalkyl substances (PFAS) in wastewater. Thus, it is urgent to develop a facile and fast method for identifying fluorosurfactants in commercially available AFFFs. In this work, fluorine nuclear magnetic resonance (19F NMR) spectroscopy was optimized to measure AFFFs directly with the extra addition of 5% D2O as the locking reagent, and high-quality spectra could be acquired within 4 min (0.1% fluorosurfactant content). Recovery experiments demonstrated that the use of different AFFFs had no marked influence on the quantitative analysis of fluorosurfactants. Such method works with low-field NMR spectroscopy (1.4 T) as well. Two-dimensional (2D) 19F COSY NMR was used to make signal assignments for different fluorosurfactant derivatives. The optimized 19F NMR could quantify the commercially available fluorosurfactants in different AFFFs, identify them being in either the perfluorooctane sulfonate (PFOS) or fluorotelomer sulfonic acid (FTS) categories, and distinguish the head-group of PFOS and FTS derivatives, which exhibits great potentials in the developments of relevant commercial detections.

Synthesis, Structure and Antiradical Activity of Functionally Substituted Hydrazides of Isonicotinic Acid

The purpose of this work is the synthesis of new isonicotinic acid hydrazones, the study of their structure, reactivity and biological screening of some synthesized compounds. The reactions leading to new N-arylidene(alkylidene) hydrazones via the condensation of isonicotinic acid hydrazide with various derivatives of aromatic aldehydes were studied. The structure of the new functionally substituted isonicotinic acid hydrazones was established by FTIR, 1H and 13C NMR, two-dimensional COSY (1H-1H) NMR spectroscopy and HMQC (1H-13C). The antiradical activity of the synthesized derivatives was studied using diphenylpycrylhydrazide radical (DPPH) assay. It was shown that N-(3- ethoxy-4-hydroxybenzylidene)isonicotinohydrazide possesses antiradical activity (IC50 (DPPH) 103.0 μM). The antiradical properties of compounds of phenolic nature are in agreement with the energies of homolytic O-H bond dissociation calculated with the use of density functional theory.

Reaction of <i>c</i>-alkyl-substituted 1,4,8,11-tetraazacyclotetradeca-4,11-dienes with carboxylic acid halides as a new method for the synthesis of <i>c</i>- and <i>N</i>-acyl-2,3,6,7-tetrahydro-1,4-diazepines

The reactions of 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene with acetic and tetrafluorobenzoic acids halides produce C - and N -acyl-substituted 1,4-diazepines. Their structure was characterized by IR, 1H, and 13C NMR spectroscopy using two-dimensional experiments 1H-13C HMQC, HMBC, and 1H-1H COSY.

Interaction of Isonicotinic Acid Hydrazide with Carboxylic Acid Anhydrides

There has been presented data on the synthesis of monoamides and cyclic imides which are derivatives of isonicotinic acid hydrazide. Cyclic anhydrides of carboxylic acids (succinic, maleic and phthalic) easily react with the hydrazide of isonicotinic acid with cycle opening, forming isonicotinoylhydrazide of dicarboxylic acids, and under more severe conditions the latter are transformed into cyclic acid imides. The structures of the synthesized compounds were studied using 1H- and 13C-NMR spectroscopy, as well as data from twodimensional COSY (1H-1H) and HMQC (1H-13C) spectra. The values of chemical shifts, multiplicity and integral intensity of 1H and 13C signals in one-dimensional NMR spectra were determined. Homo- and heteronuclear interactions confirming the structure of the studied compounds were established using spectra in the COSY (1H-1H) and HMQC (1H-13C) formats. In the approximation of the density functional B3LYP with a base set of 6-31G(d), the enthalpy of the reactions ΔHr in the absence and in the presence of a solvent — isopropanol (self-consistent reaction field method) were calculated quantum-chemically

Direct Quantitation of Phytocannabinoids by One-Dimensional 1H qNMR and Two-Dimensional 1H-1H COSY qNMR in Complex Natural Mixtures.

The widespread use of phytocannabinoids or cannabis extracts as ingredients in numerous types of products, in combination with the legal restrictions on THC content, has created a need for the development of new, rapid, and universal analytical methods for their quantitation that ideally could be applied without separation and standards. Based on previously described qNMR studies, we developed an expanded 1H qNMR method and a novel 2D-COSY qNMR method for the rapid quantitation of ten major phytocannabinoids in cannabis plant extracts and cannabis-based products. The 1H qNMR method was successfully developed for the quantitation of cannabidiol (CBD), cannabidiolic acid (CBDA), cannabinol (CBN), cannabichromene (CBC), cannabichromenic acid (CBCA), cannabigerol (CBG), cannabigerolic acid (CBGA), Δ9-tetrahydrocannabinol (Δ9-THC), Δ9-tetrahydrocannabinolic acid (Δ9-THCA), Δ8-tetrahydrocannabinol (Δ8-THC), cannabielsoin (CBE), and cannabidivarin (CBDV). Moreover, cannabidivarinic acid (CBDVA) and Δ9-tetrahydrocannabivarinic acid (Δ9-THCVA) can be distinguished from CBDA and Δ9-THCA respectively, while cannabigerovarin (CBGV) and Δ8-tetrahydrocannabivarin (Δ8-THCV) present the same 1H-spectra as CBG and Δ8-THC, respectively. The COSY qNMR method was applied for the quantitation of CBD, CBDA, CBN, CBG/CBGA, and THC/THCA. The two methods were applied for the analysis of hemp plants; cannabis extracts; edible cannabis medium-chain triglycerides (MCT); and hemp seed oils and cosmetic products with cannabinoids. The 1H-NMR method does not require the use of reference compounds, and it requires only a short time for analysis. However, complex extracts in 1H-NMR may have a lot of signals, and quantitation with this method is often hampered by peak overlap, with 2D NMR providing a solution to this obstacle. The most important advantage of the COSY NMR quantitation method was the determination of the legality of cannabis plants, extracts, and edible oils based on their THC/THCA content, particularly in the cases of some samples for which the determination of THC/THCA content by 1H qNMR was not feasible.

SYNTHESIS OF 1,2,3-TRIAZOLO-QUINOLIZIDINES BASED ON THE QUINOLIZIDINE ALKALOID LUPININE

The modification of the quinolysin alkaloid lupinine was carried out with the intro-duction of 1,2,3-triazolyl substituents for the hydroxymethylene group in the C-1 position of the quinolysin backbone. The reaction of lupinine with methanesulfochloride in the presence of triethylamine smoothly led to lupinine methanesulfonate, whose further reaction with sodium azide in DMFA led to lupinilazide. 1,3-Dipolar [4+2]-cycloaddition of the resulting azide to alkynes produced more stable 1,2,3-triazole compounds. The interaction of lupinilazide with 2-ethinylpyridine and with alcohols containing a terminal acetylene group (propargyl alcohol, 2-methylbut-3-in -2-ol or hex-5-in -1-ol) proceeded smoothly in the DMFA medium. The reactions were carried out in the presence of an aqueous solution of CuSO4 and sodium ascorbate in DMFA and allowed the corresponding 4-substituted (1S,9aR)-1H-1,2,3-triazol-1-yl to be synthesized with good yields)methyl)octahydro-1H-quinolysins. The results of studying the structural features of synthesized compounds by 1H - and 13C - NMR spectroscopy, as well as data from the two-dimensional COSY (1H-1H) and HMQC (1H-13C) spectra are presented. The values of chemical shifts, multiplicity and integral intensity of 1H and 13C signals in one-dimensional NMR spectra are determined. In the spectra of all synthesized new quinolizi-dinotriazoles, there is a peak of the fragmentary C10H17N ion (150-151 cu), corresponding to the cleavage of the molecule by the C-10 atom of the quinolizidine backbone.

A new diastereomeric type of N-morpholino-spiro derivative. Structural, spectroscopic and computational studies

N-(2-Hydroxyethyl)morpholine and chloroacetone form a new spirane compound, (R/S)-di-(N-morpholinyl-spiro-β‑hydroxy-β-methylmorpholinyl chloride) hydrate (1). The molecular structure and spectroscopic properties of this salt were characterized by the single-crystal X-ray diffraction, DFT calculations, FTIR and NMR spectroscopies. The crystals of compound 1 are monoclinic, P21/c space group. Compound 1 consists of two non-equivalent spiro units (R and S). Each unit is built of two morpholine rings joined at the N(1) spiro center. The spiro units are linked by a water molecule through the O(W)−H(WA)⋅⋅⋅Cl(1) hydrogen bond of 3.141(7) Å with R-isomer and by an unusual interaction of water with the electron pair of morpholine oxygen atom of the other S-isomer. The total energy, geometry and natural atomic charges, calculated at the B3LYP/6–311++G(d,p) level of theory, for studied compound and for R and S isomers were analyzed. The C−H⋅⋅⋅Cl contacts were confirmed by calculations based on the quantum theory of atoms in molecule (QTAIM). The 1H and 13C chemical shifts were assigned by two-dimensional techniques, COSY, HSQC and HMBC. The experimental and computed infrared spectra were compared. The potential energy distribution (PED) was used to assign the vibrational spectra. Diagrams of HOMO and LUMO are presented and discussed.

Centrosymmetric and asymmetric dimers of 5-(quinolinium)-valeric acid bromide monohydrate in crystal field and in silico

The molecular structure and properties of 5-(quinolinium)-valeric acid bromide monohydrate are characterized by X-ray diffraction, B3LYP/6–311++G(d,p) calculations, FTIR and NMR spectra. Two molecules of this compound are hydrogen bonded through two water molecules and two bromide anions into centrosymmetric dimers, which are arranged in a strongly anisotropic layered structure. The structures of monomer and dimer of the title complex are optimized at the B3LYP/6–311++G(d,p) level of theory. The conformations of the valeric acid unit in the crystalline monohydrate and in isolated molecules (monohydrates and anhydrous forms) are compared. The experimental and theoretical infrared spectra are discussed. The FTIR spectrum shows an absorption in the 3500–2700 cm−1 region attributed to the νCOOH···OH2 and νBr−···H2O. The potential energy distributions (PED) are used to assign bands in the IR spectrum of the monomer. The 1H and 13C NMR chemical shifts are assigned by two-dimensional techniques, COSY, HSQC and HMBC. Charge delocalization is analyzed using the natural bond orbital (NBO) method and it is shown in molecular electrostatic potential (MEP) maps. The bent conformations of the computed structures are characterized by the QTAIM method.

Synthesis of hydrazone derivatives of isonicotinic acid under microwave activation conditions

In the article the results of studying the reaction of the interaction of isonicotinic acid hydrazide with various derivatives of aromatic aldehydes under conditions of microwave activation in an alcohol medium were described. The results of studying the dependences of the hydrazone yield on the duration of the activation time at various microwave irradiation powers in comparison with the classical method have been presented. It was found that the main factors affecting the nature of the synthesis and the yields of the target products were the power and time of microwave activation, as well as the structural features of the reactants. For all studied reactions, the optimal conditions for obtaining the target product have been shown. As a result of a comparative analysis of the results obtained for the synthesis of new isonicotinic hydrazones, it was determined that the use of microwave irradiation contributed to an increase in the yield of the product and a decrease in the reaction time by 3-4 times than according to traditional technology. The authenticity of each product is unambiguously proved by comparing the melting point, as well as by analyzing the physico-chemical characteristics with previously synthesized hydrazone derivatives of isonicotinic acid obtained by classical synthesis methods. The structure of all synthesized compounds was studied by H-1 and C-13 NMR spectroscopy, as well as data from two-dimensional COSY (H-1-H-1) spectra and HMQC (H-1-C-13). The developed microwave method for the synthesis of hydrazone derivatives of isonicotinic acid complies with the principles of the concept of Green Chemistry.

Synthesis and Characterization of Syndiotactic Polystyrene-Polyethylene Block Copolymer.

The direct synthesis of syndiotactic polystyrene-block-polyethylene copolymer (sPS-b-PE) with a diblock structure has been achieved. The synthetic strategy consists of the sequential stereocontrolled polymerization of styrene and ethylene in the presence of a single catalytic system: cyclopentadienyltitanium(IV) trichloride activated by modified methylaluminoxane (CpTiCl3/MMAO). The reaction conditions suitable for affording the partially living polymerization of these monomers were identified, and the resulting copolymer, purified from contaminant homopolymers, was fully characterized. Gel permeation chromatography coupled with two-dimensional NMR spectroscopy COSY, HSQC, and DOSY confirmed the block nature of the obtained polymer, whose thermal behaviour and thin film morphology were also investigated by differential scanning calorimetry, powder wide angle x-ray diffraction, and atomic force microscopy.

Multinuclear Magnetic Resonance Study on Aluminium Sec-butoxide Chelated with Ethyl Acetoacetate in Various Amounts

Reactive aluminum alkoxide (ASB, aluminium sec-butoxide) was chelated using β-diketone (EAA, ethyl acetoacetate) in order to gain control over rapid hydrolysis in the course of the sol-gel process. Derived chelates were analysed using several NMR spectroscopic techniques: one-dimensional 1H, 13C, 27Al NMR and two-dimensional COSY, HSQC and DOSY. The NMR analysis enabled identification of the formed chelate species, as well as determination of their quantitative relationships. Several complexation products were observed: tris-chelated monomer, Al(EAA)3, bis-chelated dimmer, Al2(OnBu)4(EAA) 2, tris-chelated dimmer, Al2(OnBu)3(EAA)3, tetra-chelated dimmer, Al2(OnBu)2(EAA)4, and monochelated trimer, Al3(OnBu)8(EAA). Of the formed oligomer compounds, this is the first evidence of Al2(OR)3L3 in any alkoxide and β-ketoester or β-diketone combination. Aluminium sec-butoxide and ethyl acetoacetate complexes Al2(OnBu)4(EAA) 2 and Al2(OnBu)2(EAA)4 were also observed for the first time. With the increase of the EAA/ASB ratio the coordination of aluminium shifts towards six, whereas above the EAA/ASB ratio of 2.5 solely six-coordinated aluminium exists.

Sulfonated Lignin-g-Styrene Polymer: Production and Characterization.

Among sustainable alternatives for replacing fossil-based chemicals, lignin is widely available on earth, albeit the least utilized component of biomass. In this work, lignin was polymerized with styrene in aqueous emulsion systems. The reaction afforded a yield of 20 wt % under the conditions of 100 g/L lignin concentration, pH 2.5, 0.35 mol/L sodium dodecyl sulfate concentration, 5 mol/mol styrene/lignin ratio, 5 wt % initiator, 90 °C, and 2 h. The lignin-g-styrene product under the selected conditions had a grafting degree of 31 mol % of styrene, which was determined by quantitative proton nuclear magnetic resonance (NMR). The solvent addition to the reaction mixture and deoxygenation did not improve the yield of the polymerization reaction. The produced lignin-g-styrene polymer was then sulfonated using concentrated sulfuric acid. By introducing sulfonate group on the lignin-g-styrene polymers, the solubility and anionic charge density of 92 wt % (in a 10 g/L solution) and −2.4 meq/g, respectively, were obtained. Fourier-transform infrared (FTIR), static light scattering, two-dimensional COSY NMR, elemental analyses, and differential scanning calorimetry (DSC) were also employed to characterize the properties of the lignin-g-styrene and sulfonate lignin-g-styrene products. Overall, sulfonated lignin-g-styrene polymer with a high anionicity and water solubility was produced.

A putative G-quadruplex structure in the proximal promoter of VEGFR-2 has implications for drug design to inhibit tumor angiogenesis

Tumor angiogenesis is mainly regulated by vascular endothelial growth factor (VEGF) produced by cancer cells. It is active on the endothelium via VEGF receptor 2 (VEGFR-2). G-quadruplexes are DNA secondary structures formed by guanine-rich sequences, for example, within gene promoters where they may contribute to transcriptional activity. The proximal promoter of VEGFR-2 contains a G-quadruplex, which has been suggested to interact with small molecules that inhibit VEGFR-2 expression and thereby tumor angiogenesis. However, its structure is not known. Here, we determined its NMR solution structure, which is composed of three stacked G-tetrads containing three syn guanines. The first guanine (G1) is positioned within the central G-tetrad. We also observed that a noncanonical, V-shaped loop spans three G-tetrad planes, including no bridging nucleotides. A long and diagonal loop, which includes six nucleotides, connects reversal double chains. With a melting temperature of 54.51 °C, the scaffold of this quadruplex is stabilized by one G-tetrad plane stacking with one nonstandard bp, G3-C8, whose bases interact with each other through only one hydrogen bond. In summary, the NMR solution structure of the G-quadruplex in the proximal promoter region of the VEGFR-2 gene reported here has uncovered its key features as a potential anticancer drug target.

Synthesis and 1H, 13C and 15N NMR characterisation of substituted Pyrazolo[4,3-c]quinolines and related compounds

A wide range of novel and known alkyl substituted pyrazolo[4,3-c]quinolines and related compounds were synthesized. Some of these compounds can undergo tautomerism and differences have been noted in the structural assignments already published. For each of these compounds, a complete assignment was made using 1H, 13C and 15N one- and two-dimensional NMR measurements, including NOESY, COSY, 1H-13C HSQC and 1H-13C HMBC. 1H-15N HMBC NMR has proved crucial in determining the relevant tautomeric and protonated state of the compounds.

Biopolymer from marine Athelia and its application on heavy oil recovery in heterogeneous reservoir

Biopolymer produced from marine Athelia strain presented unique Pseudoplastic behaviors under extremely-high temperature and salinity conditions. Characteristic analysis with FT-IR spectroscopy, high performance liquid chromatography, 1H and 13C NMR and two-dimensional COSY and HMQC spectra showed the structure of β-(1–6) glucans. Single-factor and orthogonal experiment design were used to optimize the yield, the maximum yield of the biopolymer was 28.32 g/L with 56.64% carbon conversion rate under optimized conditions. Economic investigation demonstrated that this novel biopolymer has great potential of commercialization with the competitive cost of $2896.04-5228.94 per ton for powder. Resistance factor and residual resistance factor were evaluated with core flooding experiments showed that this biopolymer had excellent performance of plugging capacity and profile modification, and indicating the great potential of application on heavy oil recovery.

Isolation and Identification of a Volatile Compound in Habanero Pepper (Capsicum chinense).

A volatile compound was isolated from the fruit of Habanero pepper (Capsicum chinense) and related varieties and identified as 6-methyl-(E)-4-heptenyl 3-methylbutyrate by 1H and 13C NMR spectroscopy and two-dimensional NMR experiments, including HMQC, HMBC, and 1H-1H COSY. The compound has a retention index of 1387 and is one of the major volatile compounds in Habanero pepper. This compound would be useful as a new flavor.

The electronic structure of alloxan monohydrate. Spectroscopic and density functional synergic approach

In the present communication, quantitative interpretation and assignments of the electronic absorption spectra, vibrational and one- and two-dimensional NMR spectra of alloxan, are detailed. A synergic analysis based on DFT and TD-DFT calculations and the experimental findings are performed. Attempt is made to relate these spectral findings to the electronic structure of alloxan. The computed electronic spectrum predicted three well defined bands. Natural transition orbital analysis indicate an intramolecular charge transfer from npπ orbital of the water oxygen atom resulting in the short wavelength nπ* at ∼200 nm. Furthermore, UV-photoabsorption cross section for alloxan and its monohydrate are simulated. The spectrum, composed of 10 excited states, was simulated with the nuclear ensemble approximation, sampling a Wigner distribution with 300 points. The FT-IR spectrum of alloxan, measured in the solid state as KBr pellets is reported and is computed at the DFT/B3LYP/6-311++G** level of theory. All observed vibrations are assigned. The 600 MHz one- and two-dimensional COSY, 1H NMR spectra of alloxan, measured in DMSO, are reported and analyzed and computed theoretically using the GIAO method. Hydrogen-bond interactions are responsible for remarkable downfield shift of 1H NMR peaks for alloxan.

Compact NMR Spectroscopy with Shift Reagents

To simplify a nuclear magnetic resonance (NMR) spectra of the targeted molecules, spin–spin decoupling and selective isotope substitution are two distinct approaches. A third one is to increase the applied magnetic field to increase the frequency dispersion of the chemical shift range. While this is a viable option for NMR spectrometers with superconducting magnets, the new generation of compact NMR spectrometers employs permanent magnets with limited variety in field strengths between one and two Tesla. The low-frequency dispersion at these field strengths gives rise to higher order spectra more frequently than at high field. These low-field spectra can be simplified using lanthanide shift reagents, which form complexes with the substrate molecule and increase the frequency dispersion. In this work, the use of lanthanide shift reagents is demonstrated by means of one-dimensional 1H and 19F as well as two-dimensional 19F-19F COSY experiments using a new-generation compact NMR spectrometer.

Smectogenic and nematogenic liquid crystals of a new series of heterocyclic derivatives bearing an ester terminal chain: Synthesis, characterization, and theoretical study

ABSTRACTThe synthesis and mesomorphic properties of novel ester derivatives of three series heterocyclic 1,3-oxazepinediones and the 1,3-oxazepandione moiety (a–c) are described. All structures were elucidated by physical measurements and the bonding characteristics of the resulting compounds were substantiated by Fourier transform infrared spectroscopy spectroscopy. Their molecular structures are supported by the 1H and 13C NMR spectra along with two-dimensional COSY, HMQC, and HMBC.A structure-property relationship has been established and mesogenic properties were found to be dependent on the type of rings within the molecular core. Compounds1a--7a not mesogenic exhibited Cr-I upon heating and cooling, while the series compounds 1b--7b were not mesogenic and only exhibited the transition of Cr1-Cr2 upon cooling and heating. In compounds 1c--7c, the SmA observed in compounds 1c–3c with short terminal alkyl chains during heating and cooling. However, the nematic phases were formed in compounds 4c--7c. The nematic phase presence increases with the length of the terminal alkyl chain. Theoretical studies are presented in this study and are in agreement with our results.

Phenolics and Polyphenolics from Melastomataceae Species.

The Melastomataceae family, the seventh largest flowering plants, has been studied in several fronts of natural product chemistry, including terpenoids, simple phenolics, flavonoids, quinones, lignans and their glycosides, as well as a vast range of tannins or polyphenols. This review concerns the phenolic and polyphenolic metabolites described in the literature for several genera of this family, the mode of isolation and purification, and the structure elucidation of these new natural products that has been achieved by extensive spectral analyses, including ESI-MS, 1H-, 13C-NMR spectra and two-dimensional experiments, COSY, TOCSY, J-resolved, NOESY, HMQC, DEPT, and HMBC, as well as chemical and enzymatic degradations and the chemotaxonomic meaning. Finally, a general biogenetic pathway map for ellagitannins is proposed on the bases of the most plausible free radical C-O oxidative coupling.