An efficient acetic acid mediated metal-free oxidative C—H cross coupling of imidazo[1,2-a]pyridines with glyoxal hydrates has been developed under air atmosphere.The present protocol exhibits broad substrate scope,g...An efficient acetic acid mediated metal-free oxidative C—H cross coupling of imidazo[1,2-a]pyridines with glyoxal hydrates has been developed under air atmosphere.The present protocol exhibits broad substrate scope,good functional group tolerance,and enables the construction of a series of 1,2-dicarbonyl imidazo[1,2-a]pyridines in good yields.The reaction mechanism studies suggest that the reactions proceed through the electrophilic substitution and subsequent oxidation pathway.展开更多
Multi-axial differential optical absorption spectroscopy(MAX-DOAS)measurements were conducted in Xishuangbanna,Yunnan,China,between November 1,2021 and June 30,2022 to obtain vertical distributions of formaldehyde(HCH...Multi-axial differential optical absorption spectroscopy(MAX-DOAS)measurements were conducted in Xishuangbanna,Yunnan,China,between November 1,2021 and June 30,2022 to obtain vertical distributions of formaldehyde(HCHO)and glyoxal(CHOCHO).The observations show an increase in vertical column densities(VCDs)and volume mixing ratios(VMRs)for both HCHO and CHOCHO concentrations during periods of biomass combustion.The VCDs of HCHO and CHOCHO from TROPOMI are in good agreementwith the MAX-DOAS observations.(R^(2) HCHO=0.71;R^(2) CHOCHO=0.70).Regarding seasonal variations,HCHO predominantly occupies the upper layer(400-800 m)during the biomass burning,possibly attributed to the formation of secondary HCHO as the plume ascends during combustion.CHOCHO is primarily found in the lower layer(0-200 m),suggesting a longer lifespan for HCHO compared to CHOCHO,preventing the latter from diffusing to higher altitudes.Concerning the daily variation patterns,both HCHO and CHOCHO VMRs exhibited peaks at 9:00 and 13:00,which were attributed to the nighttime accumulation and midday oxidation.Furthermore,we also investigated the sources of volatile organic compounds(VOCs)using the CHOCHO to HCHO ratio(RGF).During the period of biomass burning,there are minimal differences in the daily RGF across layers,indicating that biomass burning is the predominant source.During the non-biomass burning period,the daily RGF shows significant differences among layers,indicating that emissions from biological and anthropogenic sources primarily contribute during the period.展开更多
More than a century after its initial synthesis,urea-formaldehyde(UF)resins still have dominant applications as adhesives,paints,and coatings.However,formaldehyde in this industry produces formaldehyde emissions that ...More than a century after its initial synthesis,urea-formaldehyde(UF)resins still have dominant applications as adhesives,paints,and coatings.However,formaldehyde in this industry produces formaldehyde emissions that are dangerous to health.Scientists have spent the last decade replacing formaldehyde and phenol with environmentally friendly substances such as glyoxal and tannin to create bio-based adhesives.This review covers recent advances in synthesizing glyoxal tannin-based resins,especially those made from sustainable raw material substitutes and changes made to synthetic processes to improve mechanical properties.The efficacy of using tannin-glyoxal adhesives in producing wood-based composites has been proven.The glyoxylate reaction forms cross-linked bridges between the aromatic sites of the tannin and glyoxal molecular structures.Glyoxal tannin adhesive with a greater percentage of glyoxal than tannin will produce an adhesive with better characteristics.The gel time reduces as the hardener concentration rises from 7.5%to 15%when glyoxal is used in adhesives.However,excessive amounts of glyoxal will result in a decrease in viscosity values.Glyoxal exhibits faster delivery degradation when it reaches a maximum temperature of approximately 130°C,although it initiates the curing process slightly slower at 110°C.Adding glyoxal to tannin-based adhesives can improve the mechanical properties of composite boards.The wet shear strength of the resulting plywood is increased by 105.4%with the addition of 5-weight percent tannin-based resin with glyoxal as a cross-linker in Soy Protein Adhesive.With glyoxal as a hardener,the panels produced showed good internal bond strengths(>0.35 MPa)and met the international standard specifications for interior-grade panels.展开更多
The gas phase hydration of glyoxal （HCOCHO） in the presence of sulfuric acid （H2SO4） were studied by the high-level quantum chemical calculations with M06-2X and CCSD（T） theoretical methods and the conventional ...The gas phase hydration of glyoxal （HCOCHO） in the presence of sulfuric acid （H2SO4） were studied by the high-level quantum chemical calculations with M06-2X and CCSD（T） theoretical methods and the conventional transition state theory （CTST）. The mechanism and rate constant of the five different reaction paths are consid- ered corresponding to HCOCHO＋H2O, HCOCHO＋H2O… H2O, HCOCHO… H2O＋H2O, HCOCHO＋H2O… H2SO4 and HCOCHO… H2O＋H2SOa. Results show that H2SO4 has a strong catalytic ability, which can significantly reduce the energy barrier for the hydration reaction of glyoxal. The energy barrier of hydrolysis of glyoxal in gas phase is lowered to 7.08 kcal/mol from 37.15 kcal/mol relative to pre-reactive complexes at the CCSD（T）/6- 311＋＋G（3df, 3pd）//M06-2X/6-311＋＋G（3df, 3pd） level of theory. The rate constant of the H2SO4 catalyzed hydrolysis of glyoxal is 1.34×10-11 cm3/（molecule.s）, about 1013 higher than that involving catalysis by an equal number of water molecules, and is greater than the reaction rate of glyoxal reaction with OH radicals of 1.10×10-11 cm3/（molecule·s） at the room temperature, indicating that the gas phase hydrolysis of glyoxal of H2SO4 catalyst is feasible and could compete with the reaction glyoxal＋OH under certain atmospheric condi- tions. This study may provide useful information on understanding the mechanistic features of inorganic acid-catalyzed hydration of glyoxal for the formation of oligomer.展开更多
A laser flash photolysis study of the reactivity of Cl˙with glyoxal, glyoxal mono- and dibisulfite adducts, 1-hydroxy-2, 2-diol-ethanesulfonate and 1, 2-dihydroxy-1, 2-ethanedi sulfonate in the aqueous phase was ca...A laser flash photolysis study of the reactivity of Cl˙with glyoxal, glyoxal mono- and dibisulfite adducts, 1-hydroxy-2, 2-diol-ethanesulfonate and 1, 2-dihydroxy-1, 2-ethanedi sulfonate in the aqueous phase was carried out. The obtained rate constants can be used for atmospheric modeling.展开更多
A novel vanadium oxide catalyst supported on active carbon was prepared by an incipient wetness impregnation method, and the precursor was obtained from oxalic acid aqueous solutions of NH4VO3. The catalyst was applie...A novel vanadium oxide catalyst supported on active carbon was prepared by an incipient wetness impregnation method, and the precursor was obtained from oxalic acid aqueous solutions of NH4VO3. The catalyst was applied liquid phase oxidation of glyoxal to glyoxylic acid. It was found that V2O5/C catalyst exhibited obvious activity for glyoxal oxidation. Glyoxylic acid could be obtained without pH regulation during the reaction. By using this catalyst, the conversion of glyoxal and the yield of glyoxalic acid were 29.2% and 13.6%, respectively at 313 K and oxygen flow 0.1 L/rain after reaction for 10 h.展开更多
This study presents the Multi Axis Differential Optical Absorption Spectroscopy(MAXDOAS) measurements for Glyoxal(CHOCHO) in Beijing, China(39.95°N, 116.32°E). CHOCHO is the smallest compound of di-carbonyl ...This study presents the Multi Axis Differential Optical Absorption Spectroscopy(MAXDOAS) measurements for Glyoxal(CHOCHO) in Beijing, China(39.95°N, 116.32°E). CHOCHO is the smallest compound of di-carbonyl group. As a primary sink of CHOCHO, its photolysis with NOx(oxides of nitrogen) results in the production of tropospheric ozone. Therefore,the focus of CHOCHO DOAS measurements is increasing in trend. We did the measurements from 09 May 2017 to 09 September 2017. The study was conducted to compare different retrieval settings in order to reveal best DOAS fit settings for CHOCHO;furthermore, effect of haze and non-haze days on CHOCHO concentration was examined.The root mean square of residual and Differential Slant Column density(dSCD) error was reduced when measurements were done with lower wavelength limit around 432–438 nm and upper intervals around 455–460 nm. Thus, lower wavelength intervals around432–438 nm and upper intervals around 457–460 nm were best for the retrieval of dSCDs for CHOCHO. Meteorological conditions like haze or non-haze days did not have significant effect on DOAS fit parameters. The CHOCHO vertical column densities range from 1.33 E +14 to 9.77 E + 14 molecules/cm2 during the study period with average of 6.16 E +14 molecules/cm2. The results indicated that during haze days CHOCHO concentration was higher because of lower rate of photolysis and atmospheric oxidation potential. Our results did not show any significant weekend effect on CHOCHO atmospheric concentration.展开更多
Based on the ESI-MS and ^(13)C-NMR analysis of the forms of glyoxal in acidic and alkaline solutions,the soy-based adhesive cross-linked by glyoxal was prepared in this work.The results showed that glyoxal existed in ...Based on the ESI-MS and ^(13)C-NMR analysis of the forms of glyoxal in acidic and alkaline solutions,the soy-based adhesive cross-linked by glyoxal was prepared in this work.The results showed that glyoxal existed in water in different forms at different pH levels.Under alkaline conditions,glyoxal transformed to glycolate through the intramolecular disproportionation reaction.Under acidic conditions,although some of glyoxal transformed to glycolate as what happened under alkaline conditions,most of glyoxal molecules existed in the form of fiveor six-membered cyclic ether structure.No ethylene tetraol or free aldehyde group was actually detected under these conditions.Although glyoxal reacted with soy protein under both acidic and alkaline conditions,alkaline conditions were more favorable for the improvement of mechanical performance and water resistance of soybased adhesives than acid conditions.展开更多
Formaldehyde(HCHO)and glyoxal(CHOCHO)are important oxidization intermediates of most volatile organic compounds(VOCs),but their vertical evolution in urban areas is not well understood.Vertical profiles of HCHO,CHOCHO...Formaldehyde(HCHO)and glyoxal(CHOCHO)are important oxidization intermediates of most volatile organic compounds(VOCs),but their vertical evolution in urban areas is not well understood.Vertical profiles of HCHO,CHOCHO,and nitrogen dioxide(NO_(2))were retrieved from ground-based Multi-Axis Differential Optical Absorption Spectroscopy(MAXDOAS)observations in Hefei,China.HCHO and CHOCHO vertical profiles prefer to occur at higher altitudes compared to NO_(2),which might be caused by the photochemistry-oxidation of longer-lived VOCs at higher altitudes.Monthly means of HCHO concentrations were higher in summer,while enhanced amounts of NO_(2)were mainly observed in winter.CHOCHO exhibited a hump-like seasonal variation,with higher monthly-averaged values not only occurred in warm months(July-August)but also in cold months(November-December).Peak values mainly occurred during noon for HCHO but emerged in the morning for CHOCHO and NO_(2),suggesting that HCHO is stronger link to photochemistry than CHOCHO.We further use the glyoxal to formaldehyde ratio(GFR)to investigate the VOC sources at different altitudes.The lowest GFR value is almost found in the altitude from 0.2 to 0.4 km,and then rises rapidly as the altitude increases.The GFR results indicate that the largest contributor of the precursor VOC is biogenic VOCs at lower altitudes,while at higher altitudes is anthropogenic VOCs.Our findings provide a lot more insight into VOC sources at vertical direction,but more verification is recommended to be done in the future.展开更多
The reaction mechanism of glyoxal （G） with urea （U） under weak acid condition was theoretically investigated at PW91/DNP/COSMO of quantum chemistry using density functional theory （DFT） method. The results show ...The reaction mechanism of glyoxal （G） with urea （U） under weak acid condition was theoretically investigated at PW91/DNP/COSMO of quantum chemistry using density functional theory （DFT） method. The results show that the addition reaction of G with U under the conditions mainly involves the reactions of U with protonated glyoxal （p-G）, protonated 2,2-dihy- droxyacetaldehyde （p-G 1） and protonated bis-hemdiol （p-G2） to form two important carbocation reactive intermediates of C-p-UG and C-p-UG1, and two important hydroxyl compounds of UG and UG1. These compounds play important roles in the formation of UG resin. According to the result of quantum chemical calculation, UG resin was synthesized successfully under weak acid conditions. The UG resin was characterized by matrix assisted laser desorption ionization time of flight mass spectrometry （MALDI-TOF-MS）, ultraviolet and visible spectroscopy （UV-vis）, Fourier transform infrared spectroscopy （FT1R） and nuclear magnetic resonance spectroscopy （13CNMR and 1HNMR）. These instrumental analytical results agree with each other and further confirm the addition reaction pathway of glyoxal with urea proposed by quantum chemical calculation.展开更多
Currently, modeling studies tend to significantly underestimate observed space-based glyoxal （CHOCHO） vertical column densities （VCDs）, implying the existence of missing sources of giyoxal. Several recent studies ...Currently, modeling studies tend to significantly underestimate observed space-based glyoxal （CHOCHO） vertical column densities （VCDs）, implying the existence of missing sources of giyoxal. Several recent studies suggest that the emissions of aromatic compounds and molar yields of glyoxal in the chemical mechanisms may both be underestimated, which can affect the simulated glyoxal concentrations. In this study, the influences of these two factors on glyoxal amounts over China were investigated using the RAMS-CMAQ modeling system for January and July 2014. Four sensitivity simulations were performed, and the results were compared to satellite observations. These results demonstrated significant impacts on glyoxal concentrations from these two factors. In case 1, where the emissions of aromatic compounds were increased three-fold, improvements to glyoxal VCDs were seen in high anthropogenic emissions regions. In case 2, where molar yields of glyoxal from isoprene were increased five-fold, the resulted concentrations in July were B-B-fold higher, achieving closer agreement between the modeled and measured glyoxal VCDs. The combined changes from both cases 1 and 2 were applied in case B, and the model succeeded in further reducing the underestimations of glyoxal VCDs. However, the results over most of the regions with pronounced anthropogenic emissions were still underestimated. So the molar yields of giyoxal from anthropogenic precursors were considered in case 4. With these additional mole yield changes （a two-fold increase）, the improved concentrations agreed better with the measurements in regions of the lower reaches of the Yangtze River and Yellow River in January but not in July.展开更多
The aim of this study is to analyze the various compositions of polyvinyl alcohol (PVA) and starch blends. The blends have been cross-linked with glyoxal to enhance its properties. The hydroxyl groups of PVA and starc...The aim of this study is to analyze the various compositions of polyvinyl alcohol (PVA) and starch blends. The blends have been cross-linked with glyoxal to enhance its properties. The hydroxyl groups of PVA and starch react with glyoxal via formation of acetal bonds;hence crosslinking could take place. The cross-linking of glyoxal is observed in various analytical methods such as DSC and FTIR. The cross-linked blends showed better thermal and mechanical properties. Viscosity, tensile shear strength, pencil hardness and ultimate stress were evaluated to estimate the changes due to cross-linking. It was observed that the cross-linking is directly proportional to starch, since the starch hydroxyl groups are easily accessible for reacting. The cross-linked blend showed better cohesion between its chains, thereby increasing glass transition temperature. It was reflected in the subsequent increase in tensile strength properties.展开更多
Advanced glycation end products(AGE) are potential harmful substances formed in the advanced Maillard reaction and increasingly investigated in muscle foods. However, the contribution of oxidation to the AGE formation...Advanced glycation end products(AGE) are potential harmful substances formed in the advanced Maillard reaction and increasingly investigated in muscle foods. However, the contribution of oxidation to the AGE formation is controversial. Moreover, reports on glyoxal(GO) induced AGE formation in chicken meat emulsion(CME) are limited. Thus, the effects of GO on emulsifying properties, rheological behavior and AGE formation in CME were investigated. Our findings exhibited that levels of Nε-carboxymethyllysine(CML) and Nε-carboxyethyllysine(CEL) were associated with lipid oxidation but not significantly(P > 0.05). Levels of AGE peaked when GO concentration ranged from 5 mmol/L(CML) to 10 mmol/L(CEL). The droplets’ aggregation associated with the disulfide bond when the concentration of GO was at 0.5–30 mmol/L while non-disulfide bond association occurred at 30–50 mmol/L GO concentration. In conclusion, compared to the effect of oxidation, GO exhibited the main role in the AGE formation of CME. This study will provide theoretical significance for further understanding and controlling the formation of AGE in CME.展开更多
Three possible lower barrier dissociation pathways of the deportonated glyoxylic acid in aqueous solution are predicated by means of B3LYP and CCSD（T） （single-point） methods. The calculated results suggest that th...Three possible lower barrier dissociation pathways of the deportonated glyoxylic acid in aqueous solution are predicated by means of B3LYP and CCSD（T） （single-point） methods. The calculated results suggest that the formation of formate ion is the energetically most favorable process, and that the decomposition reaction is occurring through nucleophilic attack of negatively charged carboxylic oxygen on the α-carbon. This is in good agreement with the proposed mechanisms of the mass spectrometry experiment.展开更多
The crosslinking mechanism of glyoxal and asparagine was analyzed,and the relationship between the mechanism and practical performances of soy protein-based adhesives was also discussed.It is shown that when pH=1 and ...The crosslinking mechanism of glyoxal and asparagine was analyzed,and the relationship between the mechanism and practical performances of soy protein-based adhesives was also discussed.It is shown that when pH=1 and 3,glyoxal reacted with asparagine in the form of major cyclic ether compounds.When pH=5,glyoxal reacted with asparagine in two structural forms of sodium glycollate and cyclic ether compounds.However,amidogens of asparagine were easy to develop protonation under acid conditions.Supplemented by the instability of cyclic ether compounds,the reaction activity and reaction degree between glyoxal and asparagine were relatively small.Under alkaline conditions,glyoxal mainly reacted with asparagine in the form of sodium glycollate.With the increase of pH,the polycondensation was more sufficient and the produced polycondensation products were more stable.The reaction mechanism between glyoxal and asparagine had strong correspondence to the practical performances of the adhesives.Glyoxal solution could develop crosslinking reactions with soy protein under both acid and alkaline conditions.Bonding strength and water resistance of the prepared soy protein-based adhesives were increased significantly.When pH>7,glyoxal had relatively high reaction activity and reaction intensity with soy protein,and the prepared adhesives had high crosslinking density and cohesion strength,showing relatively high bonding strength,water resistance and thermal stability.展开更多
Crosslinking is a common practice to improve the barrier properties of polymers. In this study, Montmorillonite (MMT) was used with Polyvinyl alcohol (PVA) to deposit nanocomposite coatings which were crosslinked with...Crosslinking is a common practice to improve the barrier properties of polymers. In this study, Montmorillonite (MMT) was used with Polyvinyl alcohol (PVA) to deposit nanocomposite coatings which were crosslinked with glyoxal (Gly) by Layer by Layer (LbL) on a PET substrate. Two crosslinking conditions were studied, under mild condition and with an acidic environment. Mild condition was useful to identify the reversibility steps and the optimum crosslinking times while the acidic environment was essential to investigate the crosslinking mechanism, by determining the permeability for different crosslinking times. PVA and PVA-MMT coatings showed a strong correlation between the permeability coefficients for different crosslinking times and the FTIR results.展开更多
A study of the catalytic activity of V2O5/C catalyst for the oxygen oxidation of glyoxal has been made, showing that glyoxylic acid can be formed without control of pH value and there is little oxalic acid from the ex...A study of the catalytic activity of V2O5/C catalyst for the oxygen oxidation of glyoxal has been made, showing that glyoxylic acid can be formed without control of pH value and there is little oxalic acid from the excessive oxidation of glyoxylic acid. The studies of XRD and TEM have shown that V2O5 diffraction peaks gradually strengthen with the increase of the content of V2O5. With the content of 3% V2O5 and the calcination temperature of 573 K, V2O5/C catalyst displayed the best activity and selectivity. The conversion of glyoxal and the selectivity of glyoxylic acid reached 18.76% and 77.70% after 5 h, respectively. Moreover, V2O5/C catalyst showed small deactivation after recycling three times, which indicates that V2O5/C has a higher stability than noble metal catalysts in the reaction medium.展开更多
文摘An efficient acetic acid mediated metal-free oxidative C—H cross coupling of imidazo[1,2-a]pyridines with glyoxal hydrates has been developed under air atmosphere.The present protocol exhibits broad substrate scope,good functional group tolerance,and enables the construction of a series of 1,2-dicarbonyl imidazo[1,2-a]pyridines in good yields.The reaction mechanism studies suggest that the reactions proceed through the electrophilic substitution and subsequent oxidation pathway.
基金supported by Yunnan Fundamental Research Projects(No.202101AT070003)the National Natural Science Foundation of China(No.42365007).
文摘Multi-axial differential optical absorption spectroscopy(MAX-DOAS)measurements were conducted in Xishuangbanna,Yunnan,China,between November 1,2021 and June 30,2022 to obtain vertical distributions of formaldehyde(HCHO)and glyoxal(CHOCHO).The observations show an increase in vertical column densities(VCDs)and volume mixing ratios(VMRs)for both HCHO and CHOCHO concentrations during periods of biomass combustion.The VCDs of HCHO and CHOCHO from TROPOMI are in good agreementwith the MAX-DOAS observations.(R^(2) HCHO=0.71;R^(2) CHOCHO=0.70).Regarding seasonal variations,HCHO predominantly occupies the upper layer(400-800 m)during the biomass burning,possibly attributed to the formation of secondary HCHO as the plume ascends during combustion.CHOCHO is primarily found in the lower layer(0-200 m),suggesting a longer lifespan for HCHO compared to CHOCHO,preventing the latter from diffusing to higher altitudes.Concerning the daily variation patterns,both HCHO and CHOCHO VMRs exhibited peaks at 9:00 and 13:00,which were attributed to the nighttime accumulation and midday oxidation.Furthermore,we also investigated the sources of volatile organic compounds(VOCs)using the CHOCHO to HCHO ratio(RGF).During the period of biomass burning,there are minimal differences in the daily RGF across layers,indicating that biomass burning is the predominant source.During the non-biomass burning period,the daily RGF shows significant differences among layers,indicating that emissions from biological and anthropogenic sources primarily contribute during the period.
基金funded by National Research and Innovation Agency,Republic of Indonesia,Research Grant No.65/II.7/HK/2022,titled Pengembangan Produk Oriented Strand Board Unggul dari Kayu Ringan dan Cepat Tumbuh dalam Rangka Pengembangan Produk Biokomposit Prospektif。
文摘More than a century after its initial synthesis,urea-formaldehyde(UF)resins still have dominant applications as adhesives,paints,and coatings.However,formaldehyde in this industry produces formaldehyde emissions that are dangerous to health.Scientists have spent the last decade replacing formaldehyde and phenol with environmentally friendly substances such as glyoxal and tannin to create bio-based adhesives.This review covers recent advances in synthesizing glyoxal tannin-based resins,especially those made from sustainable raw material substitutes and changes made to synthetic processes to improve mechanical properties.The efficacy of using tannin-glyoxal adhesives in producing wood-based composites has been proven.The glyoxylate reaction forms cross-linked bridges between the aromatic sites of the tannin and glyoxal molecular structures.Glyoxal tannin adhesive with a greater percentage of glyoxal than tannin will produce an adhesive with better characteristics.The gel time reduces as the hardener concentration rises from 7.5%to 15%when glyoxal is used in adhesives.However,excessive amounts of glyoxal will result in a decrease in viscosity values.Glyoxal exhibits faster delivery degradation when it reaches a maximum temperature of approximately 130°C,although it initiates the curing process slightly slower at 110°C.Adding glyoxal to tannin-based adhesives can improve the mechanical properties of composite boards.The wet shear strength of the resulting plywood is increased by 105.4%with the addition of 5-weight percent tannin-based resin with glyoxal as a cross-linker in Soy Protein Adhesive.With glyoxal as a hardener,the panels produced showed good internal bond strengths(>0.35 MPa)and met the international standard specifications for interior-grade panels.
文摘The gas phase hydration of glyoxal （HCOCHO） in the presence of sulfuric acid （H2SO4） were studied by the high-level quantum chemical calculations with M06-2X and CCSD（T） theoretical methods and the conventional transition state theory （CTST）. The mechanism and rate constant of the five different reaction paths are consid- ered corresponding to HCOCHO＋H2O, HCOCHO＋H2O… H2O, HCOCHO… H2O＋H2O, HCOCHO＋H2O… H2SO4 and HCOCHO… H2O＋H2SOa. Results show that H2SO4 has a strong catalytic ability, which can significantly reduce the energy barrier for the hydration reaction of glyoxal. The energy barrier of hydrolysis of glyoxal in gas phase is lowered to 7.08 kcal/mol from 37.15 kcal/mol relative to pre-reactive complexes at the CCSD（T）/6- 311＋＋G（3df, 3pd）//M06-2X/6-311＋＋G（3df, 3pd） level of theory. The rate constant of the H2SO4 catalyzed hydrolysis of glyoxal is 1.34×10-11 cm3/（molecule.s）, about 1013 higher than that involving catalysis by an equal number of water molecules, and is greater than the reaction rate of glyoxal reaction with OH radicals of 1.10×10-11 cm3/（molecule·s） at the room temperature, indicating that the gas phase hydrolysis of glyoxal of H2SO4 catalyst is feasible and could compete with the reaction glyoxal＋OH under certain atmospheric condi- tions. This study may provide useful information on understanding the mechanistic features of inorganic acid-catalyzed hydration of glyoxal for the formation of oligomer.
文摘A laser flash photolysis study of the reactivity of Cl˙with glyoxal, glyoxal mono- and dibisulfite adducts, 1-hydroxy-2, 2-diol-ethanesulfonate and 1, 2-dihydroxy-1, 2-ethanedi sulfonate in the aqueous phase was carried out. The obtained rate constants can be used for atmospheric modeling.
文摘A novel vanadium oxide catalyst supported on active carbon was prepared by an incipient wetness impregnation method, and the precursor was obtained from oxalic acid aqueous solutions of NH4VO3. The catalyst was applied liquid phase oxidation of glyoxal to glyoxylic acid. It was found that V2O5/C catalyst exhibited obvious activity for glyoxal oxidation. Glyoxylic acid could be obtained without pH regulation during the reaction. By using this catalyst, the conversion of glyoxal and the yield of glyoxalic acid were 29.2% and 13.6%, respectively at 313 K and oxygen flow 0.1 L/rain after reaction for 10 h.
基金supported by grants from the National Key Research and Development Program of China (Nos. 2018YFC0213104)National Natural Science Foundation of China (Nos. 41722501, 91544212, 51778596, 41575021)National Key Research and Development Program of China (Nos. 2016YFC0203302)
文摘This study presents the Multi Axis Differential Optical Absorption Spectroscopy(MAXDOAS) measurements for Glyoxal(CHOCHO) in Beijing, China(39.95°N, 116.32°E). CHOCHO is the smallest compound of di-carbonyl group. As a primary sink of CHOCHO, its photolysis with NOx(oxides of nitrogen) results in the production of tropospheric ozone. Therefore,the focus of CHOCHO DOAS measurements is increasing in trend. We did the measurements from 09 May 2017 to 09 September 2017. The study was conducted to compare different retrieval settings in order to reveal best DOAS fit settings for CHOCHO;furthermore, effect of haze and non-haze days on CHOCHO concentration was examined.The root mean square of residual and Differential Slant Column density(dSCD) error was reduced when measurements were done with lower wavelength limit around 432–438 nm and upper intervals around 455–460 nm. Thus, lower wavelength intervals around432–438 nm and upper intervals around 457–460 nm were best for the retrieval of dSCDs for CHOCHO. Meteorological conditions like haze or non-haze days did not have significant effect on DOAS fit parameters. The CHOCHO vertical column densities range from 1.33 E +14 to 9.77 E + 14 molecules/cm2 during the study period with average of 6.16 E +14 molecules/cm2. The results indicated that during haze days CHOCHO concentration was higher because of lower rate of photolysis and atmospheric oxidation potential. Our results did not show any significant weekend effect on CHOCHO atmospheric concentration.
基金This work was supported by Science-technology Support Foundation of Guizhou Province of China(Nos.[2019]2325 and [2020]1Y125)the Growth Project of Young Scientific and Technological Talents in Colleges and Universities of Guizhou Province(No.[2019]184)+1 种基金Yunnan Fundamental Research Key Projects(No.2019FA012)National Natural Science Foundation of China(Nos.31870546 and 31800481).
文摘Based on the ESI-MS and ^(13)C-NMR analysis of the forms of glyoxal in acidic and alkaline solutions,the soy-based adhesive cross-linked by glyoxal was prepared in this work.The results showed that glyoxal existed in water in different forms at different pH levels.Under alkaline conditions,glyoxal transformed to glycolate through the intramolecular disproportionation reaction.Under acidic conditions,although some of glyoxal transformed to glycolate as what happened under alkaline conditions,most of glyoxal molecules existed in the form of fiveor six-membered cyclic ether structure.No ethylene tetraol or free aldehyde group was actually detected under these conditions.Although glyoxal reacted with soy protein under both acidic and alkaline conditions,alkaline conditions were more favorable for the improvement of mechanical performance and water resistance of soybased adhesives than acid conditions.
基金the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA23020301)the National Natural Science Foundation of China(Nos.51778596,41977184,and 41941011)+5 种基金the Key Research and Development Project of Anhui Province(202104i07020002)the Anhui Science and Technology Major Project(No.18030801111)the Major Projects of High Resolution Earth Observation Systems of National Science and Technology(05-Y30B01-9001-19/20-3)the Youth Innovation Promotion Association of CAS(2021443)the Young Talent Project of the Center for Excellence in Regional Atmospheric Environment,CAS(CERAE202004)the Fundamental Research Funds for the Central Universities(No.JUSRP12042)。
文摘Formaldehyde(HCHO)and glyoxal(CHOCHO)are important oxidization intermediates of most volatile organic compounds(VOCs),but their vertical evolution in urban areas is not well understood.Vertical profiles of HCHO,CHOCHO,and nitrogen dioxide(NO_(2))were retrieved from ground-based Multi-Axis Differential Optical Absorption Spectroscopy(MAXDOAS)observations in Hefei,China.HCHO and CHOCHO vertical profiles prefer to occur at higher altitudes compared to NO_(2),which might be caused by the photochemistry-oxidation of longer-lived VOCs at higher altitudes.Monthly means of HCHO concentrations were higher in summer,while enhanced amounts of NO_(2)were mainly observed in winter.CHOCHO exhibited a hump-like seasonal variation,with higher monthly-averaged values not only occurred in warm months(July-August)but also in cold months(November-December).Peak values mainly occurred during noon for HCHO but emerged in the morning for CHOCHO and NO_(2),suggesting that HCHO is stronger link to photochemistry than CHOCHO.We further use the glyoxal to formaldehyde ratio(GFR)to investigate the VOC sources at different altitudes.The lowest GFR value is almost found in the altitude from 0.2 to 0.4 km,and then rises rapidly as the altitude increases.The GFR results indicate that the largest contributor of the precursor VOC is biogenic VOCs at lower altitudes,while at higher altitudes is anthropogenic VOCs.Our findings provide a lot more insight into VOC sources at vertical direction,but more verification is recommended to be done in the future.
基金Supported by the Key Program of the National Natural Science Foundation of China(No.30930074)National Natural Science Foundation of China(No.31260160)
文摘The reaction mechanism of glyoxal （G） with urea （U） under weak acid condition was theoretically investigated at PW91/DNP/COSMO of quantum chemistry using density functional theory （DFT） method. The results show that the addition reaction of G with U under the conditions mainly involves the reactions of U with protonated glyoxal （p-G）, protonated 2,2-dihy- droxyacetaldehyde （p-G 1） and protonated bis-hemdiol （p-G2） to form two important carbocation reactive intermediates of C-p-UG and C-p-UG1, and two important hydroxyl compounds of UG and UG1. These compounds play important roles in the formation of UG resin. According to the result of quantum chemical calculation, UG resin was synthesized successfully under weak acid conditions. The UG resin was characterized by matrix assisted laser desorption ionization time of flight mass spectrometry （MALDI-TOF-MS）, ultraviolet and visible spectroscopy （UV-vis）, Fourier transform infrared spectroscopy （FT1R） and nuclear magnetic resonance spectroscopy （13CNMR and 1HNMR）. These instrumental analytical results agree with each other and further confirm the addition reaction pathway of glyoxal with urea proposed by quantum chemical calculation.
基金supported by the National Natural Science Foundation of China (No. 91544221)the National Key R&D Programs of China (Nos. 2017YFC0209803, 2017YFC0210000)the CAS Strategic Priority Research Program Grant (No. XDB05020000)
文摘Currently, modeling studies tend to significantly underestimate observed space-based glyoxal （CHOCHO） vertical column densities （VCDs）, implying the existence of missing sources of giyoxal. Several recent studies suggest that the emissions of aromatic compounds and molar yields of glyoxal in the chemical mechanisms may both be underestimated, which can affect the simulated glyoxal concentrations. In this study, the influences of these two factors on glyoxal amounts over China were investigated using the RAMS-CMAQ modeling system for January and July 2014. Four sensitivity simulations were performed, and the results were compared to satellite observations. These results demonstrated significant impacts on glyoxal concentrations from these two factors. In case 1, where the emissions of aromatic compounds were increased three-fold, improvements to glyoxal VCDs were seen in high anthropogenic emissions regions. In case 2, where molar yields of glyoxal from isoprene were increased five-fold, the resulted concentrations in July were B-B-fold higher, achieving closer agreement between the modeled and measured glyoxal VCDs. The combined changes from both cases 1 and 2 were applied in case B, and the model succeeded in further reducing the underestimations of glyoxal VCDs. However, the results over most of the regions with pronounced anthropogenic emissions were still underestimated. So the molar yields of giyoxal from anthropogenic precursors were considered in case 4. With these additional mole yield changes （a two-fold increase）, the improved concentrations agreed better with the measurements in regions of the lower reaches of the Yangtze River and Yellow River in January but not in July.
文摘The aim of this study is to analyze the various compositions of polyvinyl alcohol (PVA) and starch blends. The blends have been cross-linked with glyoxal to enhance its properties. The hydroxyl groups of PVA and starch react with glyoxal via formation of acetal bonds;hence crosslinking could take place. The cross-linking of glyoxal is observed in various analytical methods such as DSC and FTIR. The cross-linked blends showed better thermal and mechanical properties. Viscosity, tensile shear strength, pencil hardness and ultimate stress were evaluated to estimate the changes due to cross-linking. It was observed that the cross-linking is directly proportional to starch, since the starch hydroxyl groups are easily accessible for reacting. The cross-linked blend showed better cohesion between its chains, thereby increasing glass transition temperature. It was reflected in the subsequent increase in tensile strength properties.
基金supported by Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX21_0579)the China Scholarship Council(No.202006850022)+1 种基金supported by Agriculture Research System of China(CARS-41-Z)Science and Technology Project of Nanjing City(No.202002040)。
文摘Advanced glycation end products(AGE) are potential harmful substances formed in the advanced Maillard reaction and increasingly investigated in muscle foods. However, the contribution of oxidation to the AGE formation is controversial. Moreover, reports on glyoxal(GO) induced AGE formation in chicken meat emulsion(CME) are limited. Thus, the effects of GO on emulsifying properties, rheological behavior and AGE formation in CME were investigated. Our findings exhibited that levels of Nε-carboxymethyllysine(CML) and Nε-carboxyethyllysine(CEL) were associated with lipid oxidation but not significantly(P > 0.05). Levels of AGE peaked when GO concentration ranged from 5 mmol/L(CML) to 10 mmol/L(CEL). The droplets’ aggregation associated with the disulfide bond when the concentration of GO was at 0.5–30 mmol/L while non-disulfide bond association occurred at 30–50 mmol/L GO concentration. In conclusion, compared to the effect of oxidation, GO exhibited the main role in the AGE formation of CME. This study will provide theoretical significance for further understanding and controlling the formation of AGE in CME.
基金supported by the Research Project of Department of Education of Heilongjiang Province (No.11531415).
文摘Three possible lower barrier dissociation pathways of the deportonated glyoxylic acid in aqueous solution are predicated by means of B3LYP and CCSD（T） （single-point） methods. The calculated results suggest that the formation of formate ion is the energetically most favorable process, and that the decomposition reaction is occurring through nucleophilic attack of negatively charged carboxylic oxygen on the α-carbon. This is in good agreement with the proposed mechanisms of the mass spectrometry experiment.
基金Funded by the National Natural Science Foundation of China(No.32160348)the Department Program of Guizhou Province(No.ZK[2021]162)+1 种基金the Guizhou Province Science and Technology Plan Project(No.[2020]1Y128)the Forestry Department Foundation of Guizhou Province of China(Nos.J[2022]21 and[2020]C14)。
文摘The crosslinking mechanism of glyoxal and asparagine was analyzed,and the relationship between the mechanism and practical performances of soy protein-based adhesives was also discussed.It is shown that when pH=1 and 3,glyoxal reacted with asparagine in the form of major cyclic ether compounds.When pH=5,glyoxal reacted with asparagine in two structural forms of sodium glycollate and cyclic ether compounds.However,amidogens of asparagine were easy to develop protonation under acid conditions.Supplemented by the instability of cyclic ether compounds,the reaction activity and reaction degree between glyoxal and asparagine were relatively small.Under alkaline conditions,glyoxal mainly reacted with asparagine in the form of sodium glycollate.With the increase of pH,the polycondensation was more sufficient and the produced polycondensation products were more stable.The reaction mechanism between glyoxal and asparagine had strong correspondence to the practical performances of the adhesives.Glyoxal solution could develop crosslinking reactions with soy protein under both acid and alkaline conditions.Bonding strength and water resistance of the prepared soy protein-based adhesives were increased significantly.When pH>7,glyoxal had relatively high reaction activity and reaction intensity with soy protein,and the prepared adhesives had high crosslinking density and cohesion strength,showing relatively high bonding strength,water resistance and thermal stability.
文摘Crosslinking is a common practice to improve the barrier properties of polymers. In this study, Montmorillonite (MMT) was used with Polyvinyl alcohol (PVA) to deposit nanocomposite coatings which were crosslinked with glyoxal (Gly) by Layer by Layer (LbL) on a PET substrate. Two crosslinking conditions were studied, under mild condition and with an acidic environment. Mild condition was useful to identify the reversibility steps and the optimum crosslinking times while the acidic environment was essential to investigate the crosslinking mechanism, by determining the permeability for different crosslinking times. PVA and PVA-MMT coatings showed a strong correlation between the permeability coefficients for different crosslinking times and the FTIR results.
基金Supported by the Technology Research and Development Project for University of Shanxi Province of China (Grant No. 20051272)
文摘A study of the catalytic activity of V2O5/C catalyst for the oxygen oxidation of glyoxal has been made, showing that glyoxylic acid can be formed without control of pH value and there is little oxalic acid from the excessive oxidation of glyoxylic acid. The studies of XRD and TEM have shown that V2O5 diffraction peaks gradually strengthen with the increase of the content of V2O5. With the content of 3% V2O5 and the calcination temperature of 573 K, V2O5/C catalyst displayed the best activity and selectivity. The conversion of glyoxal and the selectivity of glyoxylic acid reached 18.76% and 77.70% after 5 h, respectively. Moreover, V2O5/C catalyst showed small deactivation after recycling three times, which indicates that V2O5/C has a higher stability than noble metal catalysts in the reaction medium.
