Hydrogen Nuclear Magnetic Resonance Spectra Research Articles

Identification and quantification of IEPOX in ambient aerosols, using electron and chemical ionization sources GC/MS as their trimethylsilyl ethers, and using H-NMR

Isoprene is the most abundant non-methane hydrocarbon (NMHC) emitted by vegetation, and the precursor that makes the greatest contribution to secondary organic aerosols (SOA) in the troposphere. Atmospheric oxidation of isoprene produces a series of reactive intermediates, isoprene epoxydiols (IEPOX). The reactive uptake of IEPOX is the significant formation pathway of atmospheric SOA. In this work, four isomers of IEPOX were synthesized, derivatized by silylation reagents, and measured by gas chromatography/mass spectrometry (GC/MS). The electron-impact (EI) and methane chemical ionization (CI) sources mass spectra of trimethylsilyl ester (TMS) derivatives of IEPOX isomers were obtained and the fragmentation behaviors of the derivatives were examined. Moreover, the hydrogen nuclear magnetic resonance (H-NMR) spectra of IEPOX isomers were also obtained and the peak intensities in the H-NMR spectra were analyzed. Based on the standard spectra, IEPOX isomers were identified in ambient PM2.5 aerosols in the Gongga Mountain (China). The peak sequence of TMS derivatives of IEPOX isomers in GC/MS chromatogram was δ4-IEPOX, δ1-IEPOX, cis-β-IEPOX and trans-β-IEPOX. The isomers with the highest concentrations were δ1-IEPOX (threo- and erythro-). The mass ratios of IEPOX to 2-methyltetrols were 0.02–6.0 and the concentrations of IEPOX were 0.8–41.6 ng/m3 in the PM2.5 aerosols. The current study verified the core roles of IEPOX as active intermediates in photo oxidation of isoprene in ambient atmosphere.

Effects of methacrylic anhydride gelatin hydrogel loaded with silver and recombinant human basic fibroblast growth factor on deep partial-thickness burn wounds in rabbits

Effects of methacrylic anhydride gelatin hydrogel loaded with silver and recombinant human basic fibroblast growth factor on deep partial-thickness burn wounds in rabbits

Simple pyrolysis of polystyrene into valuable chemicals

Abstract Overuse of polymer products has led to severe environmental problems, which are threatening survival of creatures on earth. It is urgent to tackle enormous polymer wastes with proper cycling methods. Pyrolysis of polymers into high-value chemicals and fuels is displaying great potential to address the white pollution issue. In this study, we focus on chemical recycling of polystyrene, an important polymer in our everyday life, into valuable chemicals through simple pyrolysis strategy under nitrogen protection. It is found that yield of liquid product from polystyrene pyrolysis achieves as high as 76.24%, and there exists single component in the liquid product, which has been identified as styrene through hydrogen nuclear magnetic resonance spectra. Moreover, we propose monomer dissociation mechanism to explain the pyrolysis process of polystyrene based on the structure of polystyrene and experimental results.

Effects of Highly Oxygenated Water in a Hyperuricemia Rat Model.

Recent years have seen a rapidly rising number of oxygenated water brands that claim to impart health benefits and increase athletic performance by improving oxygen availability in the body. Drinks with higher dissolved oxygen concentrations have in recent times gained popularity as potential ergogenic aids, despite the lack of evidence regarding their efficacy. The aim of this study was to characterize oxygenated water and assess the improvement in uric acid metabolism while identifying performance enhancements in animals administered oxygenated water. Oxygenated water was characterized by hydrogen and oxygen nuclear magnetic resonance (NMR) spectroscopy. Hyperuricemia in rats was induced by treatment with oxonic acid potassium salt, and the animals were given oxygenated drinking water before, during, or after oxonic acid treatment. Serum uric acid was measured to confirm the effects on uric acid metabolism. Following oxygenation, the full width at half maximum (FWHM) was reduced to 11.56 Hz and 64.16 Hz in the hydrogen and oxygen NMR spectra, respectively. Oxygenated water molecule clusters were reduced in size due to the reduction in FWHM. Oxygen concentration did not vary significantly with increased temperature. However, standing time played a critical role in the amount of oxygen dissolved in the water. The rat studies indicated that oxygenated water reduced serum uric acid levels and their rate of increase and enhanced uric acid metabolism. A significant improvement in uric acid metabolism and rate of increase in serum uric acid concentration was observed in hyperuricemic rats administered oxygenated water compared to that in rats administered regular water. High oxygen concentrations enhanced the rate of oxygen absorption, leading to increased glycolysis and mitochondrial protein synthesis. Therefore, oxygenated water is a potential adjuvant therapy or health food for treatment of hyperuricemia.

Two benzoyl coumarin amide fluorescence chemosensors for cyanide anions

Two new benzoyl coumarin amide derivatives with ortho hydroxyl benzoyl as terminal group have been synthesized. Their photophysical properties and recognition properties for cyanide anions in acetonitrile have also been examined. The influence of electron donating diethylamino group in coumarin ring and hydroxyl in benzoyl group on recognition properties was explored. The results indicate that the compounds can recognize cyanide anions with obvious absorption and fluorescence spectral change and high sensitivity. The import of diethylamine group increases smartly the absorption ability and fluorescence intensity of the compound, which allows the recognition for cyanide anions can be observed by naked eyes. The in situ hydrogen nuclear magnetic resonance spectra combining photophysical properties change and job's plot data confirm that Michael addition between the chemosensors and cyanide anions occurs. Molecular conjugation is interrupted, which leads to fluorescence quenching. At the same time, there is a certain extent hydrogen bond reaction between cyanide and hydroxyl group in the compounds, which is beneficial to the recognition.

Coumarin amide derivatives as fluorescence chemosensors for cyanide anions

Four coumarin amide derivatives with 4-methyl coumarin or pyrene as terminal group have been synthesized. Their photophysical properties and recognition properties for cyanide anions have been examined. The results indicate that the compounds can recognize cyanide anions with obvious absorption and fluorescence spectra change, at the same time, obvious color and fluorescence change can be observed by naked eye. The in situ hydrogen nuclear magnetic resonance spectra and photophysical properties change confirm that Michael additions between the chemosensors and cyanide anions take place at the 4-position of coumarin.

Cholesteric Cyclohexane-Containing Side-Chain Liquid-Crystalline Polysiloxanes

Two new kinds of Cholesteric cyclohexane-Containing Side-Chain Liquid-Crystalline Polysiloxanes (PAand PB) were synthesized via hydrosilylation reaction of polymethyl hydrogen siloxane with cyclohexane mesogenic monomers (MAand MB). The yield of PA, PBwere 71.6%, 82.5% and 81.0%, respectively. The molecular structures of MAand MB, PAand PBwere investigated by Fourier transform infrared spectroscopy (FTIR) and hydrogen-nuclear magnetic resonance spectra (1H-NMR). The corresponding liquid crystalline phase type was also observed by polarizing optical microscopy (POM) and X-ray diffraction (XRD). The liquid crystalline phase behavior and thermal properties of the polymers were analyzed by differential scanning calorimetry (DSC). Results showed that MAand MBexhibited multicolor platelet texture of a blue phase and cholesteric phase, and the Tmand Tiof MAand MBincreased with the increasing flexible chain length. The mesophase temperature range of PAand PBwas broader than that of MAand MB. PAexhibited a rare nematic phase----spherulite texture of polymeric smectic A phase. PBwere of cholesteric and nematic---- cholesteric phase. The Tmand Tiof PAand PBincreased with the increasing flexible spacer groups.

Design and synthesis of water‐soluble photosensitive α‐cyclodextrin and its application in dispersing carbon nanotubes

ABSTRACTThis manuscript describes the use of a novel water‐soluble photosensitive α‐cyclodextrin modified coumarin (α‐CD‐C) to disperse carbon nanotubes (CNTs) in water. First, using epichlorohydrin as the bridged unit, water‐soluble α‐cyclodextrin (α‐CD) was introduced to modify 7‐hydroxy‐4‐methylcoumarin and prepare α‐CD‐C. α‐CD‐C was characterized with hydrogen nuclear magnetic resonance spectra (1H‐NMR) and High pressure liquid chromatography‐mass spectrometry. The photodimerization experiment showed that α‐CD‐C could photodimerize upon 365 nm irradiation, and then photo‐de‐crosslink upon the subsequent 254 nm irradiation. Next, α‐CD‐C was used to disperse CNTs in water. Transmission electron microscope and scanning electron microscope demonstrated that α‐CD‐C effectively adsorbed onto the surface of CNTs. The α‐CD‐C is an efficient dispersant for CNTs. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2588–2593, 2013

Metabolic profiling in the roots of coffee plants exposed to the coffee root-knot nematode, Meloidogyne exigua

To understand the effect of nematode Meloidogyne exigua infestation on coffee plants, resistant and susceptible coffee seedlings were inoculated with second-stage juveniles of M. exigua, and root metabolites were studied for four time intervals at 0, 24, 48 and 96 h. During this important period for parasite establishment, the concentrations of phenols, carbohydrates, amino acids and alkaloids in the roots were measured, and hydrogen nuclear magnetic resonance spectra of the root extracts were used to identify and quantify other metabolites. One of the most striking changes was the concentration of fumaric acid on resistant plants, which varied from 59 μg g(of root)−1 to 138 μg g(of root)−1 during the first 24 h of the nematode inoculation. The same level of variation was observed much later (96 h) in susceptible plants. Similarly, formic and quinic acid concentrations increased more rapidly in the resistant plants compared to the susceptibles. Sucrose concentrations increased to 370 % in the first 48 h in the resistant plants but showed no significant variation in the susceptible plant. Besides, the concentration of alkaloids was much higher at 24 and 48 h in the susceptibles compared to the resistant plants. These results suggest that the higher production of sucrose as well as formic, fumaric and quinic acids, and the lower production of alkaloids by the resistant cultivar in the first 48 h after the nematode inoculation are associated with the resistance of coffee plants to M. exigua.

Synthesis and Properties of Disodium Mono-fatty Alcohol Citrate

Abstract The long reaction time and low conversion of the existing technologies in indirect synthesis of disodium mono-fatty alcohol citrate constrain their industrialized application. Here, we developed a new technology and synthesized a series of monoester of citric acid salts different carbon atoms in hydrophobic group. The structures of intermediate and products were defined by infrared spectra and hydrogen nuclear magnetic resonance spectra. Their physico-chemical properties were systematically studied for the first time, including equilibrium surface tension, wetting ability, emulsification stability and foaming behavior in aqueous solution. The results show that ifs the number of carbon atoms in the hydrophobic group increases, the critical micelle concentration (CMC) decreases, wetting ability weakens, the foaming volume in hard water increases and emulsification stability for liquid paraffin and bean oil increases, but opposite for oil acid.

Study on the Structure and Liquid Crystal Behavior of Cyclohexane Liquid Crystal Monomer

Chemical structure and liquid crystal behavior of mesogenic monomer(Trans, trans)-4-propyl-4’-vinyl- bicyclohexane(3HHV) with platelet texture of a blue phase and mesogenic monomer(Trans, trans)-4-propyl-4’-propenyl –bicyclohexane(4HHV) with cholesteric phase were studied. The chemical structure of mesogenic monomers were determined by Fourier transform infrared spectroscopy, and Hydrogen-nuclear magnetic resonance spectra. Liquid crystal behavior of mesogenic monomers were analyzed by polarizing optical microscopy and X-ray diffraction. Thermal properties of mesogenic monomers were researched by differential scanning calorimetry. The results were that: 3HHV showed the platelet texture of a blue phase was considerably different from single color texture of blue phase we always refer to, and assuredly belong to a new kind of blue phase liquid crystal. These two kinds of cyclohexane liquid crystal monomer also showed good thermal stability.

The structural characterization and its influence on photoluminescence of lithium tetra-(8-hydroxy-quinolinato) Boron

Lithium tetra-(8-hydroxy-quinolinato) boron (LiBq4) is one kind of blue light-emitting material with good performances. In this paper, LiBq4 sample was synthesized and purified. The purity is up to 97.6%. In order to investigate the influence of LiBq4 structure on its optical characteristics, especially on the shift of photoluminescence (PL) central wavelength, compared with that of tris-(8-hydroquinoline) aluminum (Alq3), a joint experiment based on a combination of X-ray diffraction (XRD) spectrum, infrared absorption (IRA) spectrum, hydrogen nuclear magnetic resonance (HNMR) spectrum, absorption and photoluminescence spectra of LiBq4 was performed. IRA and HNMR spectra generally make certain the molecular structure, and illuminate the interaction among the atoms in LiBq4. Absorption and photoluminescence spectra qualitatively suggest the basic optical characteristic of LiBq4 and that the emitted light results from 8-hydroxyquinoline rings. By comparing LiBq4 with Alq3, the conclusion that besides B−N covalent bond, B−O is another important factor which heavily influence on the PL peak can be drawn. Furthermore, the influence of LiBq4‘s special coupling manner on PL peak is demonstrated too.

Synthesis and characterization of tris-(8-hydroxyquinoline)aluminum

A comprehensive understanding of the characteristics of the organic electroluminescent (EL) material tris-(8-hydroxyquinoline)aluminum (Alq 3) is meaningful for organic light-emitting devices (OLEDs). Thin films of Alq 3 are among the most efficient EL molecular films known to date. Alq 3 sample was synthesized and purified. The purity of Alq 3 is up to 98.5%. The electronic structure and interaction in Alq 3 molecule have been studied. The results of a joint experimental investigation based on a combination of X-ray diffraction (XRD) spectra, hydrogen nuclear magnetic resonance (HNMR) spectra, infrared absorption (IRA) spectra, mass spectra (MS), X-ray emission (XRE) spectra and fluorescence spectra of Alq 3 have been obtained. The analysis on HNMR spectra of Alq 3 demonstrated that the coordinate interaction between Al 3+ and O ion is more intensive than that between Al 3+ and N ion. The AlO bond is covalent bond in Alq 3 molecule. Alq 3 has two types of geometrical isomers, namely mer isomer and fac isomer. IRA spectra of Alq 3 indicate a very intensive chelation of aromatic ring. From the MS spectra the ratio of charge to mass of Alq 3 was obtained. Fluorescence data confirmed the existence of a fluorescent species formed between Al ion and 8-hydroxyquinolinol.

ChemInform Abstract: HYDROGEN NUCLEAR MAGNETIC RESONANCE SPECTRA AND CONFORMATIONS OF DEOXYALDITOLS IN DEUTERIUM OXIDE

Chemischer InformationsdienstVolume 16, Issue 48 Physical Organic Chemistry ChemInform Abstract: HYDROGEN NUCLEAR MAGNETIC RESONANCE SPECTRA AND CONFORMATIONS OF DEOXYALDITOLS IN DEUTERIUM OXIDE D. G. GILLIES, D. G. GILLIESSearch for more papers by this authorD. LEWIS, D. LEWISSearch for more papers by this author D. G. GILLIES, D. G. GILLIESSearch for more papers by this authorD. LEWIS, D. LEWISSearch for more papers by this author First published: December 3, 1985 https://doi.org/10.1002/chin.198548050AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume16, Issue48December 3, 1985 RelatedInformation

Conversion of a Varian 40 Mc/s high resolution nuclear magnetic resonance spectrometer to 80 Mc/s operation

The conversion of a 40 Mc/s Varian nuclear magnetic resonance spectrometer to 80 Mc/s operation is described. The increase in maximum field strength from 12 to 22.5 kG was achieved by the use of conical Permendur pole caps. The factors affecting pole-cap geometry are discussed. Sufficient field homogeneity for the production of high resolution 80 Mc/s hydrogen nuclear magnetic resonance spectra was achieved with Golay electric shim coils. Further stability of the magnetic field, enabling spectra to be recorded on precalibrated chart paper, was achieved by a double audio-frequency modulation technique. Notes are also given on the associated changes required to the electronic circuits.

Nuclear magnetic resonance studies on geometrical isomers of paraldehyde and other substituted trioxanes

The cis-cis and the cis-trans geometrical isomers of the cyclic trimer of acetaldehyde have been identified by means of their hydrogen nuclear magnetic resonance spectra. Ordinary paraldehyde has been found to be the cis-cis isomer with equatorial methyl groups. This is called the β-isomer. In addition, the α-isomer and six other substituted trioxanes have been investigated. The NMR spectra of these six were analyzed satisfactorily assuming a “chair” conformation for the ring and a cis-cis arrangement of substituents.

The analysis of the nuclear magnetic resonance spectra of some saturated and unsaturated hydrocarbon groupings

Detailed analyses of the hydrogen nuclear magnetic resonance spectra of some substituted ethanes and substituted ethylenes (vinyl compounds) have yielded the magnitudes and relative signs of the inter-proton coupling constants. These show regularities that are related to the stereochemical configurations of adjacent pairs of CH bonds.