Methoxyl Groups Research Articles

Thermodynamic-Dominated Stereoselective Gridization of Molecular Nanolinkage Based on Fluorenes

AbstractThe path-selectivity and stereoselectivity of gridization pathways into fluorene-based drawing hand grids (DHGs-F) are precisely modulated through tuning acid conditions and side-chain effects. BF3·OEt2 supports the realization of the gridization path (rac-DHG1-F, yield: 82%, meso-DHG1-F, yield: 11%). On the contrary, CF3SO3H will lead to the enhancements in polymerization pathways (about 85% yield). When the side chain is a methoxyl group, rac-DHG1-F and meso-DHG1-F will be obtained. However, when the side chain is a group without an oxygen atom, only rac-DHGs-F can be obtained (de = 100%). Moreover, through excitonic physical properties, rac-DHGs-F exhibits a more π-electronic delocalization, potentially serving as the intriguing tactic strategy to modulate the optoelectronic properties.

Anti-Angiogenic and Cytotoxicity Effects of Selachyl Alcohol Analogues

The active ingredients in the shark liver oil (SLO) mixture were found to be a group of etherlinked glycerol known as alkylglycerols (AKGs). During the last century, initial clinical use of the SLO mixture was for treating leukemias and later preventing radiation sickness from cancer x-ray therapy. Selachyl alcohol is one of the most abundant AKGs in the SLO mixture and it displayed strong activity in reducing lung metastasis number on a model of grafted tumor in mice (Lewis lung carcinoma cells). In this study, selachyl alcohol analogue containing methoxyl (7), gem-difluorinated (8), azide (9) and hydroxyl (10) group at the 12 position in the alkyl chain were synthesized and compared regarding their cytotoxicity and anti-migratory effects on Human Umbilical Vein Endothelial Cell line. AKGs 7-10 were synthesized according to the literature procedure. The cytotoxicity of the studied AKGs was evaluated by the MTT test and Human Umbilical Vein Endothelial Cell line (HUVEC) was used as an in vitro model to evaluate their anti-migratory effects. The four AKGs have substantially the same toxicity threshold (≥ 12 μM), whereas they have an anti-migratory activity significantly different on endothelial cells. AKGs 9 and 10 significantly reduce the chemotactic migration induced by VEGF, but analogue (10) containing the hydroxyl group at the 12 position in the alkyl chain was the most potent anti-VEGF inhibitor. We presented here a series of four synthetic selachyl alcohol analogues, among which AKGs 9 and 10 showed the ability to inhibit endothelial cell migration. The relationship structures and anti-VEGF effects of these analogues were also evaluated and discussed. Unnatural synthesized AKGs could be explored as one new source of anticancer agents.

Primary care service use during adolescence and young adulthood: Tertiary care cohort affected by chronic health conditions.

To understand use of family physician services and emergency department visits by adolescents and young adults with chronic health conditions. Longitudinal retrospective observational cohort study using administrative health data. Chronic care clinics at a tertiary care pediatric hospital in Calgary, Alta. In total, 1326 adolescents who were between 12 and 15 years old in 2008, who were observed until 2016, and who received medical services for chronic conditions were enrolled in the study. Eligible participants had at least 4 visits to the same chronic disease clinic in any 2-year window before age 18. Group-based trajectory modeling was used to identify groups of adolescents with distinct patterns of health care use (for visits to emergency departments and to primary care practices), while 2 tests explored trajectory group differences (eg, sex, location of residence). Median age was 14 years (range 12 to 17 years) at study entry, and 22 years (range 14 to 24 years) at study exit. Half were female and most (85.4%) lived in an urban area. Median observation period was 8.7 person-years (range 1.3 to 9.1 years). Group-based trajectory modeling identified 5 distinct trajectory groups of primary care use and 4 groups of emergency services use. Groups differed by sex and location of residence in each trajectory model. Many adolescents increased their use of emergency services between the ages of 12 and 24 years, with distinct patterns of primary care use being observed. Association of additional patient- and system-level factors (eg, disease severity, distance to nearest family physician office) should be explored.

Ligand-Promoted Nickel-Catalyzed para-Selective Carboxylation of Anisoles

It has always been a challenge in free radical chemistry to control site selectivity during the reaction of free radicals with aromatic rings. Herein, we report the site-selective carboxylation of anisoles through the direct reaction of the bromoform radical with a benzene ring at the para position under the assistance of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline with nickel(II) as the catalyst. A wide variety of anisoles were compatible, leading to para-carboxylated products in moderate to good yields. A preliminary mechanistic study suggested that the Ni(II) complex coordinates with the methoxyl group of the aromatic ring, which may have increased the steric hindrance at the ortho and meta positions, while this weak interaction reduces the aromaticity of the aromatic ring, affording an activated phenyl ring, thereby leading to highly para-selective carboxylation.

Pyrolysis mechanism law of β-O-4 lignin dimer model compounds: A density functional theory study

Lignin is the second abundant natural renewable after cellulose. Pyrolysis is usually transformed lignin into high value-added platform compounds. In order to fully utilized lignin, the pyrolysis mechanism needs an in-depth understanding. Herein we performed density function theory (DFT) calculation to unveil the initial mechanism of pyrolysis of 9 representative β − O− 4 lignin dimer model compounds with phenyl-1, 3-propanediol as the main body. Several cleavage pathways were investigated, including Cβ−O bond breaking（Cβ−O bond homolysis reaction, Maccoll elimination reaction and retro-ene fragmentation reaction） and Cα−Cβ bond breaking. Results show that the substituents on the B-ring have a greater effect on the pyrolysis pathway of lignin dimer than that on the A-ring. When no substituent on the ortho-position of B-ring, the retro-ene fragmentation reaction is the dominant pathway. And, its main reason is these structures have no steric hindrance in the process of hydrogen transfer. The Cβ−O bond homolysis is the dominant pathway when methoxy group exists on ortho-position of B-ring. Maccoll elimination reaction also has certain advantages due to the influence of electronic factors of methoxyl group on ortho-position of B-ring. The cleavage reaction of Cβ−O bond is always prior to that of Cα−Cβ bond. The effect of water molecules on the pyrolysis reaction has been also discussed. The results showed that H2O could promote the Maccoll elimination I reaction, but did not change the dominant pyrolysis mechanism.

Synthesis, characterization, and utilization of poly-amino acid-functionalized lignin for efficient and selective removal of lead ion from aqueous solution

Effectively removing heavy metals from the wastewater using a green low-cost natural polymer-based adsorbent received a great deal of attention. In this study, natural γ-polyglutamic acid (γ-PGA) and ε-poly-L-lysine (ε-PL) functionalized lignin (DLGS and DLLS) were synthesized through demethylation/phenolation and amination to increase its intrinsic reactivity and adsorption sites, which were used to remove heavy metals from aqueous solutions. DLGS and DLLS were comprehensively characterized by 31P, 2D HSQC NMR, and elemental analysis (EA). The adsorption property of DLGS and DLLS for Pb2+ have been systematically investigated. The adsorption kinetics and isotherms were compliant with the pseudo-second-order model and Langmuir isotherm model, respectively. The maximum adsorption capacity of DLGS and DLLS for Pb2+ was 275.9 and 231.8 mg g−1 at 298 K, respectively, which is higher than that of most of the lignin-based adsorbent reported. Furthermore, it is confirmed that DLGS and DLLS exhibit excellent selectivity for removing Pb2+ through competitive adsorption experiments. Based on the Fourier transform infrared spectrum (FTIR) and X-ray photoelectron spectroscopy (XPS) and the density functional theory (DFT) calculations, the hydroxyl, carboxyl, amino, methoxyl, and dithiocarbamate groups are contributed to the binding with Pb2+, and density functional theory calculation further suggested dithiocarbamate and the carboxyl group are the primary active sites.

Application of the in-situ biological detoxification polymer for the improvement of AFB1 detoxification

A novel biological detoxification polymer (BDP) was in-situ synthesis by the co-immobilization of the compound enzymes (laccase and Aspergillus niger crude enzyme) and the aminated mesoporous silica nanoparticles (MSN-NH2) with zeolitic imidazolate framework-8 (ZIF-8) for the detoxification of aflatoxin B1 (AFB1). The ZIF-8 shell of BDP acted as the AFB1 adsorbent around the compound enzymes inside the BDP. The detoxification rate of BDP at 35 °C for 24 h was 96.7%. The detoxification of AFB1 with the added mass ratio of BDP 1% to moldy corn was 65.8%. After the BDP was stored at 4 °C for 30 d, the enzyme activity remained 70.9%. Moreover, the enzyme activity and detoxification rate with BDP remained 80.7% and 80.0%, respectively, after the fourth repeated detoxification. The compound enzymes acted on the C–O bond and methoxyl group in the side chain of AFB1. Three degradation products (C16H16O5, C16H14O4, C15H14O2) with different structures were detected in the degradation of AFB1 with the BDP. Application of the in-situ BDP represents a promising way to improve the detoxification of AFB1.

Synthesis, characterization and anti-bacterial activity of Schiff Base and its mixed ligand complexes of Cr (II) and Co (II) containing vanillin and 2-aminophenol

Schiff Base are organic ligand that contained azomethine linkage (-HC=N-) which shows biological importance. Schiff Base from vanillin and 2-aminophenol was synthesized in 1:1 mole ratio. The complexes of Cr (II) and Co (II) from Schiff Base in 1:2 mole ratio metal-ligand (M-L) and the mixed ligand complexes from Schiff Base and 2-aminophenol in 1:1:1 mole ratio ligand-metal-ligand(L-M-L) were synthesized and characterized based on solubility, melting point, conductivity, Fourier transform infrared spectroscopy (FTIR) and ultraviolet (UV). The solubility result shows that, dimethyl sulfoxide(DMSO) dissolved all the complexes. The results obtained from melting point, conductivity indicated purity and non-electrolytic of the complexes respectively. In metal complexes, the infrared data showed the ligands is coordinated to the metal ion through azomethine nitrogen, oxygen in methoxyl group and oxygen in phenolic group. In mixed ligand complexes, the infrared data revealed the ligands is coordinated to the metal ion through azomethine nitrogen, oxygen in methoxyl group, oxygen in phenolic group and nitrogen in amino group. The results showed a six coordinate octahedral geometry for these complexes. The ligands and the metal complexes were examined for their antibacterial activity using agar well diffusion method against Escherichia coli, Staphylococcus aureus, streptococcus pyrogens , Klebsiella pneumonia (gram - bacteria), and Bacillus sutilis, Staphylococcus aureus (gram + bacteria). In comparing the results, the complex of Co(HL1)2 has greater zone of inhibition against the tested organism than the free ligands as antibacterial agent.

Ancient Biosyntheses in an Oil Crop: Glucosinolate Profiles in Limnanthes alba and Its Relatives (Limnanthaceae, Brassicales).

The glucosinolate (GSL) profiles of four Limnanthaceae species, including the oil crop Limnanthes alba (meadowfoam), were investigated by an ultrahigh-performance liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (UHPLC-QToF-MS/MS) analysis of desulfoGSLs after desulfation of native GSLs, supplemented by NMR of desulfated 2-hydroxy-2-methylpropylGSL and 3-methoxybenzylGSL. Leaves, roots, and seeds were investigated, providing an overview of biosynthetic capabilities in the genera Floerkea and Limnanthes. Methoxyl groups on benzylGSLs were in meta but not para positions; two 3,5-disubstituted benzylGSLs are tentatively proposed. 2-Hydroxy-2-methylpropylGSL was accompanied by an isomer that was not a previously reported GSL. The combined GSL profile of the family included GSLs derived from valine, leucine, isoleucine, phenylalanine, and tyrosine, and possibly methionine and tryptophan. Substituted indole GSLs and GSLs derived from chain-elongated amino acids or alanine were searched for but not detected. Hypothetic glycosides of GSLs were detected at low levels. Based on biochemical interpretation, we suggest biosynthetic schemes and gene families (CYP79C, GSOH) relevant for tailoring GSL profiles in Limnanthes crops.

Nucleophilic Substitution at Heteroatoms-Identity Substitution Reactions at Phosphorus and Sulfur Centers: Do They Proceed in a Concerted (SN2) or Stepwise (A-E) Way?

The mechanisms of three selected identity substitution reactions at phosphorus and sulfur occurring with stereospecific inversion have been investigated using density functional theory (DFT). The first identity reaction between methoxyl anion and methyl ethylphenylphosphinate 1 reported in 1963 has been shown to proceed in a stepwise fashion according to the addition–elimination (A–E) mechanism involving formation of a pentacoordinate phosphorus intermediate (TBI-1). In contrast, the results of DFT studies of the identity chloride exchange reaction in (ethoxy)ethylphosphonochloridothionate 3 in acetone solution provided evidence that it proceeds synchronously according to the classical Ingold’s SN2-P mechanism. DFT calculations of the methoxyl–methoxy exchange reaction at sulfur in methyl p-toluenesulfinate 4 catalyzed by trifluoroacetic acid in methanol revealed that it proceeds stepwise (A–E mechanism), involving the formation of the high-coordinate sulfurane intermediate. In both identity transesterification reactions, 1 and 4, the transiently formed trigonal bipyramidal intermediates with the two methoxyl groups occupying apical positions (TBI-1 and TBI-4) have higher free energy barriers for the Berry-type pseudorotation than those for direct decomposition to starting phosphinate and sulfinate ensuring stereospecific inversion of configuration at the phosphinyl and sulfinyl centers. Thus, the DFT method proved its usefulness in the distinction between both mechanisms that are often indistinguishable by kinetic measurements.

Structural Analysis of Lignin-Based Furan Resin.

The global “carbon emission peak” and “carbon neutrality” strategic goals promote us to replace current petroleum-based resin products with biomass-based resins. The use of technical lignins and hemicellulose-derived furfuryl alcohol in the production of biomass-based resins are among the most promising ways. Deep understanding of the resulting resin structure is a prerequisite for the optimization of biomass-based resins. Herein, a semiquantitative 2D HSQC NMR technique supplemented by the quantitative 31P NMR and methoxyl group wet chemistry analysis were employed for the structural elucidation of softwood kraft lignin-based furfuryl alcohol resin (LFA). The LFA was fractionated into water-insoluble (LFA-I) and soluble (LFA-S) parts. The analysis of methoxyl groups showed that the amount of lignin was 85 wt% and 44 wt% in LFA-I and LFA-S fractions, respectively. The HSQC spectra revealed the high diversity of linkages formed between lignin and poly FA (pFA). The HSQC and 31P results indicated the formation of new condensed structures, particularly at the 5-position of the aromatic ring. Esterification reactions between carboxyl groups of lignin and hydroxyl groups of pFA could also occur. Furthermore, it was suggested that lignin phenolic hydroxyl oxygen could attack an opened furan ring to form several aryl ethers structures. Therefore, the LFA resin was produced through crosslinking between lignin fragments and pFA chains.

Solving the lignin waste crisis: Utilization of lignin to produce value- added antioxidant agents

Lignin is a major component of biomass that is considered a huge energy and carbon reserve. Aside from being the second most abundant polymer in nature, it is a major by- product of pulping, paper and other forestry- based industries with about 70 million tons per year. Due to it being highly biologically recalcitrant, lignin is underutilized and considered a waste product that is solely incinerated for power generation. Establishment of a market for lignin- based, value- added chemicals was a necessity. Because of its renewable nature, availability, and richness in phenolic component, however, it is considered as an attractive alternative for antioxidant activity. In our research, all types of extracted lignin exhibited a value ranging from 2.21 to 11.47 on the AAI assay suggesting high antioxidant activity. Furthermore, special chemical structures such as hydrogen atoms, double bonds between side chain carbons, as well as the presence of methoxyl groups can increase antioxidant activity by 2- 3 folds via means of radical scavenging. Finally, lignin extracted at higher temperature (~95C and greater) exhibited higher ORAC values compared to lignin extracted at lower temperature; ORAC values of 1072.32 to 3119.68 versus 1741.72 to 1745.11, respectively. This paper is going to shed more light on the lignin antioxidant properties, where it stems from, what affects it, as well as future directions and possible interdisciplinary potential improvement.

Extraction of Lignin from Empty Fruit Bunch Fiber via Microwave-Assisted Acid Hydrotrope Solvent

Lignin is a sub-product from lignocellulose apart from cellulose and hemicellulose that produced from empty fruit bunch fiber (EFB). Lignin has low solubility and reactivity due to its bulky macromolecule structre. Being one of the wastes that being generated in massive amount, many alternatives has been taken to transform lignin into valuable products. To do so, many reactions are needed for the lignin to go through. In this study, lignin will be extracted from empty fruit bunch (EFB) with the aid of acid hydrotrope concentration of 30 % and microwave assisted with various extraction heating time and temperature. Characterization of lignin is done using Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric analysis (TGA), Differential Scanning Calorimetry (DSC) and Nuclear magnetic resonance (NMR) while Scanning Electron Microscopy (SEM) and X-ray Powder Diffraction (XRD) used to characterize residues. The highest percentage of lignin yield and its purity obtained are 19.47 % and 96.63 % with the reaction time and temperature of the microwave is 30 minutes and 90 °C. From Fourier Transform Infrared Spectroscopy (FTIR), a wide band at 3430.09 cm-1 and 3413.45 cm-1 are observed due to O-H stretching vibration. As for peak at 1123.17 cm-1 and 1051.26 cm-1, it correspond to syringyl and guaicyl unit in both lignin and raw EFB. As for Thermogravimetric analysis (TGA), it shows that lignin decomposes slowly compared to raw EFB due to the aromatic structure of lignin that is very stable, therefore leading to difficulty of decomposing while from Differential Scanning Calorimetry (DSC), after removing cellulose and hemicellulose, glass transition temperature (Tg) obtained from lignin DSC spectroscopy is 193.05 °C at heat flow of 1.15 mW/mg. Next, from Nuclear magnetic resonance (NMR) spectroscopy, the signals observed around 6.5 – 8.0 ppm indicate aromatic H in syringyl and guaiacyl unit only at lignin spectra while at 3.3 – 4.0 ppm, raw EFB has an intense peak compared to lignin which attribute to methoxyl group. When the residue of the lignin as well as the raw EFB powder is characterized using X-ray Powder Diffraction (XRD), the crystallinity index of the lignin with reaction time and temperature of the microwave 30 minutes and 90 °C is the highest, 69.28 %. As a conclusion, an admissible percent of lignin yield and purity is able to be obtained with addition of acid hydrotrope depending on the variables. From the spectroscopies characterization, it is proved that lignin characteristics and properties are compatible for the production of new and value added products.

ISOLATION AND PHYSICOCHEMICAL CHARACTERIZATION OF PECTIN FROM NONCONVENTIONAL NATU-RAL RAW MATERIALS

Obtaining and studying the functional properties and determining the subsequent purpose in the practical use of pectin substances requires a thorough study of physical and chemical characteristics of the polysaccharide.
 By using the acidic hydrolysis method, pectic polysaccharides were isolated from nonconventional raw materials of natural origins - basidial fungus mushrooms Fomes fomentarius, Ganoderma lucidum, Inonotus hispidus, Polýporus squamosus. The polysaccharides isolated were characterized: such as content of free and etherifying carboxyl groups, total -СООН groups, -ОСН3 groups, degree of etherification and by data of the IR-spectroscopy.
 The pectic polysaccharides isolated in identical conditions from the basidial mushrooms were powders with colors from light yellow to is light-brown by the appearance, possess sub-acidic taste, have no extraneous smack and a smell. The pectin from Inonotus hispidus was much lighter than other pectins (Fomes fomentarius, Ganoderma lucidum, Polýporus squamosus). The pectin’s isolated were similar to the apple pectin by the organoleptic properties. They can classified as averagely etherified pectins regarding the degree etherification. Etherification degree of the studied pectins was in the range of 50.00–66.67%. The methoxyl groups were ranged between 8.47–11.43%. Content of free carboxylic groups in the range of 2.25–5.40%.

EVALUATION OF ANTI-MICROBIAL POTENTIAL OF STRUCTURALLY MODIFIED DERIVATIVES OF LEAD COMPOUND BERBERINE ISOLATED FROM ROOTS OF BERBERIS ARISTATA

The alkaloid berberine, the chief constituent of Berberis aristata, has been reported to have antimicrobial activity associated with it. Structural changes can be made to this lead compound to try to improve its effi cacy in terms of antimicrobial activity. In the present study, attempts have been made to evaluate anti-microbial potential of structurally modifi ed derivatives of berberine. The derivatives so synthesized were characterized on the basis of spectral techniques like 1H,13C NMR, UV, IR and MASS and by comparison with standard berberine. Structure-activity relationship studies revealed that methoxyl group is pharmacophore of berberine and is thus needed to be retained in the skeleton. Further incorporation of the electron-withdrawing group has pronounced effect on the antimicrobial activity. Further attempts could be made to extend the series with the incorporation of such electron-withdrawing groups to get potent antimicrobial agents.

Two novel mono-hydroxyl pyranoanthocyanidins bearing dimethylamino substituent(s) for dye-sensitized solar cell

Two novel analogues (AF3-1 and AF3-2) of natural pigments that were originally found in wine product, pyranoanthocyanidins, were designed based on pyrano-4′-dimethylamino-10-phenyl-flavylium (AF3) by respectively introducing another electron donor(s), dimethylamino and two methoxyl groups, to the phenyl moiety. They were synthesized and then successfully applied as sensitizers in DSSC to study effect of the additional donor(s) on the DSSC performance for such pyranoanthocyanidin. The introduced second dimethylamino substituent of AF3-1 slightly red shifts the absorption spectrum. Both title dyes show relatively strong ability to shield the photoanode surface from electrolyte and to restrain the electron recapture process. Yet it is difficulty for them to adsorb on the semiconductor surface effectively and to avoid undesirable dye aggregation. DSSCs based on the designed pyranoanthocyanidin turn out to have much higher Voc but decreased Jsc compared to AF3. PCE of DSSC assembled with the better of the two pyranoanthocyanidins, AF3-1, is 1.79%, on the same level as that of the reference sensitizer.

Hydroxypropylmethylcellulose as a film and hydrogel carrier for ACP nanoprecursors to deliver biomimetic mineralization

Demineralization of hard tooth tissues leads to dental caries, which cause health problems and economic burdens throughout the world. A biomimetic mineralization strategy is expected to reverse early dental caries. Commercially available anti-carious mineralizing products lead to inconclusive clinical results because they cannot continuously replenish the required calcium and phosphate resources. Herein, we prepared a mineralizing film consisting of hydroxypropylmethylcellulose (HPMC) and polyaspartic acid-stabilized amorphous calcium phosphate (PAsp-ACP) nanoparticles. HPMC which contains multiple hydroxyl groups is a film-forming material that can be desiccated to form a dry film. In a moist environment, this film gradually changes into a gel. HPMC was used as the carrier of PAsp-ACP nanoparticles to deliver biomimetic mineralization. Our results indicated that the hydroxyl and methoxyl groups of HPMC could assist the stability of PAsp-ACP nanoparticles and maintain their biomimetic mineralization activity. The results further demonstrated that the bioinspired mineralizing film induced the early mineralization of demineralized dentin after 24 h with increasing mineralization of the whole demineralized dentin (3–4 µm) after 72–96 h. Furthermore, these results were achieved without any cytotoxicity or mucosa irritation. Therefore, this mineralizing film shows promise for use in preventive dentistry due to its efficient mineralization capability.Graphical

Substituent effect induced the distinctive ESIPT reaction and photophysical property of N-salycilidene-5-chloroaminopyridine

Two novel molecules (SCLPY-MeO and SCLPY-CN) are designed based on the N-salycilidene-5-chloroaminopyridine (SCLPY) via introducing the methoxyl (–OCH3) and cyano (-CN) groups at the meta-position of the chlorine atom, respectively, to explore the effect of the substitution of electron-withdrawing and donating groups on the excited-state intramolecular proton transfer (ESIPT) mechanism and photophysical properties of SCLPY, employing the density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods. The significant calculated structural parameters associated with the intramolecular hydrogen bonds (IHBs) have demonstrated that the IHBs intensity is enhanced in the excited state and SCLPY is endowed with the strongest IHB. The partial quenching of the short-wavelength fluorescence in SCLPY-CN has been satisfactorily explained by calculating the transition electric dipole moment and the long-wavelength fluorescence of that exhibits the largest Stokes shifts relative to the other molecules. Moreover, introducing the –OCH3 group has evidently enhanced the luminescent intensity of SCLPY. On account of the potential energy curves (PECs), scanning with gradually elongating the O1-H2 bond, it can be known that the forward proton transfer process is more readily to occur in the S1 state due to the relatively lower energy barriers compared with the ground state. Moreover, SCLPY is provided with the lowest energy barrier, implying that the ESIPT behavior is most likely inclined to proceed in SCLPY. Therefore, it is well illustrated that the introductions of –OCH3 and –CN groups indeed have an impact on the ESIPT process and photophysical properties of SCLPY.

A surprise from the deep.

Isotope patterns of methoxyl groups reveal the origin an d production potential of methane from coal.

Synthesis of phosphorus/nitrogen containing intumescent flame retardants from p-hydroxybenzaldehyde, vanillin and syringaldehyde for rigid polyurethane foams

Intumescent flame retardants (IFR) with phosphorus (P)/nitrogen (N)-containing diphenols (DH, DV and DS) were synthesized from p-hydroxybenzaldehyde (H), vanillin (V) and syringaldehyde (S) with different methoxyl groups on its aromatic ring. The FTIR, 1H NMR, 13C NMR, XPS methods were used to characterize the structures of IFR, and LOI, CCT, SEM, TG methods were used to investigate the flame retardancy and thermal stability of rigid polyurethane (RPU) foams when the three IFR were incorporated into RPU foams.Compared with H, V and S, the DH, DV and DS FTIR spectra showed absorption peaks at 3450 cm−1, 1160 cm−1, and 1222 cm−1, 1050 cm−1 and 740 cm−1, respectively, which attributed to NH, CN, and P = O, P-O, P-C groups. The 1H NMR spectra of DH, DV and DS showed proton signals at 4.8 and 6.0 ppm, which were corresponding to H1 and H2 of CN groups, and corresponding C1 signal appeared around 62.3 ppm in the 13C NMR spectra. The XPS spectra of DH, DV, DS showed peaks at 285, 398 eV and 133.5, 532 eV, which may be due to corresponding C1s, N1s of CN groups and P2p and O1s of P-O-C groups, respectively. These results indicated that the target compounds P/N-containing diphenols DH, DV and DS were synthesized successfully. Flame retardancy index (FRI) values of RPU-DH, RPU-DV, and RPU-DS were 2.33, 2.30 and 2.43, respectively, suggesting that DH, DV, and DS were good flame retardant additives. The THR and HRR values of RPU-DH, RPU-DV, RPU-DS foams were much lower than that of RPU foam. The fire growth rate (FIGRA) of RPU-DH, RPU-DV, and RPU-DS was 29.4%, 30.3%, and 24.4% lower comparing to RPU foam. The LOI value of RPU foam was 19%, while LOI values of RPU-DH, RPU-DV and RPU-DS foams increased to around 26%. These results suggested that the flame retardancy of RPU foams were improved by incorporating DH, DV, and DS. Compared with RPU foam, the CY600 of RPU-DH, RPU-DV and RPU-DS foams increased by 215.2%, 152.2% and 195.6%, respectively, and the char residue after CCT were much compact and homogeneous, which could reduce heat and mass transfer, protecting underlying materials from further combustion in a fire.In conclusion, the P/N-containing diphenols DH, DV and DS were synthesized successfully, and they were good flame retardant additives. The char residue of RPU-DH, RPU-DV and RPU-DS foams increased remarkably, and formed compact and homogeneous char layer. The flame retardancy and thermal stability of RPU-DH, RPU-DV, RPU-DS foams were improved by incorporating DH, DV, and DS.