Autoxidation of cycloalkanes （C5-C8） with molecular oxygen under catalyst-free and solvent-free conditions was conducted systematically for the first time, focusing on the autoxidation temperature and product distri...Autoxidation of cycloalkanes （C5-C8） with molecular oxygen under catalyst-free and solvent-free conditions was conducted systematically for the first time, focusing on the autoxidation temperature and product distribution. The autoxidation of cyclopentane, cyclohexane, cycloheptane and cyclooctane occurs at 120 ℃, 130 ℃, 120 ℃, and 105 ℃ respectively, with obvious oxidized products formation. At 140 ℃, 145 ℃, 130 ℃ and 125 ℃, acceptable yields of the oxidized products could be obtained for them, and the oxidized product distributions were investigated in detail. The autoxidation of cycloalkanes follows the pseudo-first-order kinetic model and the apparent activation energies （Ea） for the autoxidation of cyclopentane and cyclohexane are 159.76 kJ. tool-1 and 86.75 kJ. mol-1 respectively. This study can act as an important reference in screen of suitable reaction temperature and comparison of the performance of various catalysts in the catalytic oxidation of cycloalkanes in the attempt to enhance the oxidized product selectivity.展开更多
Methanol and detergent are chosen to be additives for the catalysts derived from active carbon supported MgO and cobalt phthalocyanine (CoPc) or CoPc/NaY zeolite, and dramatically improved the activity and stability o...Methanol and detergent are chosen to be additives for the catalysts derived from active carbon supported MgO and cobalt phthalocyanine (CoPc) or CoPc/NaY zeolite, and dramatically improved the activity and stability of catalyst in autoxidation of 1-octanelhiol.展开更多
The configuration of the hydroxy acid 2, a product from base-catalyzed autoxidation of 3α,5-cyclo-5α-cholestane-6-one,was established on the basis of NMR techniques and the mechanism of the formation of 2 was discus...The configuration of the hydroxy acid 2, a product from base-catalyzed autoxidation of 3α,5-cyclo-5α-cholestane-6-one,was established on the basis of NMR techniques and the mechanism of the formation of 2 was discussed.展开更多
The antioxidation activity of vitamin E, vitamin C and lipophilic derivatives of vitaminC, i.e. ascorbyl--6-caprylate, 6-laurate and 6-palmitate, on the autoxidation of linoleic acidwere studied in SDS, Triton X-100 a...The antioxidation activity of vitamin E, vitamin C and lipophilic derivatives of vitaminC, i.e. ascorbyl--6-caprylate, 6-laurate and 6-palmitate, on the autoxidation of linoleic acidwere studied in SDS, Triton X-100 and CTAB micelles. The effect of the lipophilicity ofthe antioxidants and micellar effects on the antioxidation activity are discussed.展开更多
Dairy products contain lipids rich in polyunsaturated fatty acids and their esters are easily oxidized by molecular oxygen over time. Deleterious changes in dairy products caused by lipid oxidation include not only lo...Dairy products contain lipids rich in polyunsaturated fatty acids and their esters are easily oxidized by molecular oxygen over time. Deleterious changes in dairy products caused by lipid oxidation include not only loss of flavour or development of off-flavours, but also loss of colour, nutrient value, and the accumulation of compounds, which may be detrimental to the health of consumers. One of the most effective ways of retarding lipid oxidation in dairy products is to incorporate antioxidants. Sometimes synthetic phenolic antioxidant, butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) are used to delay this oxidation. Supplementation dairy products with natural antioxidants (polyphenolic compounds) are better using than synthetic antioxidant and could be potentially. The use of rosemary as natural antioxidant in dairy products can reduce the rate of lipid oxidation and hydrolysis besides may be beneficial in increasing the shelf life of these products. This supplementation will move these products into the functional food area under new category as healthy dairy products. This literature review covers the research that has focused on rosemary as antioxidant and anti-inflammatory agent that can inhibit the lipid oxidation and have health benefits by preventing carcinogens from binding to DNA, fight and stop pain. In this review, we survey the previous studies that were conducted on the application of rosemary extract as an antioxidant to extend the shelf life and to minimize nutritional losses of dairy product.展开更多
Water-soluble b-alanine C60 adducts were synthesized, and the scavenging ability to superoxygen anion radical O2- and hydroxyl radical.OH were studied by autoxidation of pyrogallol and chemiluminescence, respectively....Water-soluble b-alanine C60 adducts were synthesized, and the scavenging ability to superoxygen anion radical O2- and hydroxyl radical.OH were studied by autoxidation of pyrogallol and chemiluminescence, respectively. It was found thatβ-alanine C60 adducts showed an excellent efficiency in eliminating superoxygen anion radical and hydroxyl radical. The 50% inhibition concentration (IC50) for superoxygen anion radical and hydroxyl radical were 0.15 mg/mL and 0.048 mg/mL, respectively. The difference should be mainly attributed to the different scavenging mechanisms.展开更多
The rare earth-containing composite elastomer was obtained by the reaction of vinyl pyridine-SBR (PSBR) latex with rare earth alkoxides, and its thermal oxidation resistance was studied. After aging test, it is found ...The rare earth-containing composite elastomer was obtained by the reaction of vinyl pyridine-SBR (PSBR) latex with rare earth alkoxides, and its thermal oxidation resistance was studied. After aging test, it is found that its retention rate of mechanical properties is far higher than that of the control sample. The results of thermogravimetric analysis show that its thermal-decomposing temperature rises largely. The analysis of oxidation mechanisms indicates that the main reasons for thermal oxidation resistance are that rare earth elements are of the utility to discontinue autoxidation chain reaction and that the formed complex structure has steric hindrance effect on oxidation.展开更多
Linalool,a high-reactivity volatile chemical product(VCP)commonly found in cleaning products and disinfectants,is increasingly recognized as an emerging contaminant,especially in indoor air.Understanding the gas-phase...Linalool,a high-reactivity volatile chemical product(VCP)commonly found in cleaning products and disinfectants,is increasingly recognized as an emerging contaminant,especially in indoor air.Understanding the gas-phase oxidation mechanism of linalool is crucial for assessing its impact on atmospheric chemistry and human health.Using quantum chemical calculations and computational toxicology simulations,we investigated the atmospheric transformation and toxicity evolution of linalool under low and high NO/HO_(2)·levels,representing indoor and outdoor environments.Our findings reveal that linalool can undergo the novel mechanisms involving concerted peroxy(RO_(2)·)and alkoxy radical(RO·)modulated autoxidation,particularly emphasizing the importance of cyclization reactions indoors.This expands the widely known RO_(2)·-dominated H-shift-driven autoxidation and proposes a generalized autoxidation mechanism that leads to the formation of low-volatility secondary organic aerosol(SOA)precursors.Toxicological analysis shows that over half of transformation products(TPs)exhibited higher carcinogenicity and respiratory toxicity compared to linalool.We also propose time-dependent toxic effects of TPs to assess their long-term toxicity.Our results indicate that the strong indoor emission coupled with slow consumption rates lead to significant health risks under an indoor environment.The results highlight complex indoor air chemistry and health concerns regarding persistent toxic products during indoor cleaning,which involves the use of linalool or other VCPs.展开更多
Wines contain significant amounts of polyphenols which autoxidize upon contact with oxygen,producing hydrogen peroxide.We checked more than 40 samples of white and red wines finding,on average,production of small amou...Wines contain significant amounts of polyphenols which autoxidize upon contact with oxygen,producing hydrogen peroxide.We checked more than 40 samples of white and red wines finding,on average,production of small amounts of hydrogen peroxide within 3 h after the wines had contacted with air,though some samples did not produce detectable amounts of H_(2)O_(2).The increase in hydrogen peroxide concentration after 3-h incubation of wines after opening ranged from -3.09 to 6.60μM.Wines showed also the ability of hydrogen peroxide scavenging,which can be partly attributed to sulfite.Thus,the measured net production of hydrogen peroxide in wine is a result of the actual production and scavenging of hydrogen peroxide.展开更多
Thermokinetics of the dismutation of superoxide anion (O 2 .- ) catalyzed by superoxide dismutase (SOD), in which the decomposition of hydrogen peroxide catalyzed by catalase is utilized as a source of oxygen and the ...Thermokinetics of the dismutation of superoxide anion (O 2 .- ) catalyzed by superoxide dismutase (SOD), in which the decomposition of hydrogen peroxide catalyzed by catalase is utilized as a source of oxygen and the autoxidation of pyrogallod as a source of the substrate (O 2 .- ), has been studied by microcalorimetry. The molar reaction enthalpies of the SOD reaction and the pyrogallol autoxidation have been measured as - 160.1 and - 218 kJ · mol-1, respectively, at 298. 15 K and pH 7.0. A novel method for the determination of SOD activity, the microcalorimetric assay for SOD, has been proposed. The experimental results showed that SOD had no effect on both kinetic parameters and the mechanism for the pyrogallol autoxidation. This autoxidation followed the second-order reaction kinetics in the presence of limited oxygen (the first order with respect to both pyrogallol and O2), and the second-order rate constants were hermined at 298.15 K and pH 8.0 to be 1.25 and 1.30 L·mol-1·s-1 in the absence and presence of SOD, respectively. A possible mechanism for the autoxidation of pyrogallol inhibited by SOD was also suggested.展开更多
Novel 2,2-bis-C-functionalized chain glucosid-3-uloses have been synthesized in the form of ketal. The synthesis is rather convenient through one pot multistep reactions and no expensive reagents are involved. The pro...Novel 2,2-bis-C-functionalized chain glucosid-3-uloses have been synthesized in the form of ketal. The synthesis is rather convenient through one pot multistep reactions and no expensive reagents are involved. The products are formed via autoxidation-Michael addition mechanism and their structures were characterized by X-ray crystallographic analysis. Their crystal stuctures are stablilized by intermolecular hydrogen bonds and double-strand supramolecular stacking is observed.展开更多
基金Supported by the National Natural Science Foundation of China(Grant No.21476270,21306176,21776259,21276006)Scientific Research Launching Foundation of Zhejiang University of Technology(Grant No.G2817101103)
文摘Autoxidation of cycloalkanes （C5-C8） with molecular oxygen under catalyst-free and solvent-free conditions was conducted systematically for the first time, focusing on the autoxidation temperature and product distribution. The autoxidation of cyclopentane, cyclohexane, cycloheptane and cyclooctane occurs at 120 ℃, 130 ℃, 120 ℃, and 105 ℃ respectively, with obvious oxidized products formation. At 140 ℃, 145 ℃, 130 ℃ and 125 ℃, acceptable yields of the oxidized products could be obtained for them, and the oxidized product distributions were investigated in detail. The autoxidation of cycloalkanes follows the pseudo-first-order kinetic model and the apparent activation energies （Ea） for the autoxidation of cyclopentane and cyclohexane are 159.76 kJ. tool-1 and 86.75 kJ. mol-1 respectively. This study can act as an important reference in screen of suitable reaction temperature and comparison of the performance of various catalysts in the catalytic oxidation of cycloalkanes in the attempt to enhance the oxidized product selectivity.
文摘Methanol and detergent are chosen to be additives for the catalysts derived from active carbon supported MgO and cobalt phthalocyanine (CoPc) or CoPc/NaY zeolite, and dramatically improved the activity and stability of catalyst in autoxidation of 1-octanelhiol.
文摘The configuration of the hydroxy acid 2, a product from base-catalyzed autoxidation of 3α,5-cyclo-5α-cholestane-6-one,was established on the basis of NMR techniques and the mechanism of the formation of 2 was discussed.
基金Project supported by the National Natural Science Foundation of China and the State Education Commission Doctoral Foundation of China.
文摘The antioxidation activity of vitamin E, vitamin C and lipophilic derivatives of vitaminC, i.e. ascorbyl--6-caprylate, 6-laurate and 6-palmitate, on the autoxidation of linoleic acidwere studied in SDS, Triton X-100 and CTAB micelles. The effect of the lipophilicity ofthe antioxidants and micellar effects on the antioxidation activity are discussed.
文摘Dairy products contain lipids rich in polyunsaturated fatty acids and their esters are easily oxidized by molecular oxygen over time. Deleterious changes in dairy products caused by lipid oxidation include not only loss of flavour or development of off-flavours, but also loss of colour, nutrient value, and the accumulation of compounds, which may be detrimental to the health of consumers. One of the most effective ways of retarding lipid oxidation in dairy products is to incorporate antioxidants. Sometimes synthetic phenolic antioxidant, butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) are used to delay this oxidation. Supplementation dairy products with natural antioxidants (polyphenolic compounds) are better using than synthetic antioxidant and could be potentially. The use of rosemary as natural antioxidant in dairy products can reduce the rate of lipid oxidation and hydrolysis besides may be beneficial in increasing the shelf life of these products. This supplementation will move these products into the functional food area under new category as healthy dairy products. This literature review covers the research that has focused on rosemary as antioxidant and anti-inflammatory agent that can inhibit the lipid oxidation and have health benefits by preventing carcinogens from binding to DNA, fight and stop pain. In this review, we survey the previous studies that were conducted on the application of rosemary extract as an antioxidant to extend the shelf life and to minimize nutritional losses of dairy product.
文摘Water-soluble b-alanine C60 adducts were synthesized, and the scavenging ability to superoxygen anion radical O2- and hydroxyl radical.OH were studied by autoxidation of pyrogallol and chemiluminescence, respectively. It was found thatβ-alanine C60 adducts showed an excellent efficiency in eliminating superoxygen anion radical and hydroxyl radical. The 50% inhibition concentration (IC50) for superoxygen anion radical and hydroxyl radical were 0.15 mg/mL and 0.048 mg/mL, respectively. The difference should be mainly attributed to the different scavenging mechanisms.
文摘The rare earth-containing composite elastomer was obtained by the reaction of vinyl pyridine-SBR (PSBR) latex with rare earth alkoxides, and its thermal oxidation resistance was studied. After aging test, it is found that its retention rate of mechanical properties is far higher than that of the control sample. The results of thermogravimetric analysis show that its thermal-decomposing temperature rises largely. The analysis of oxidation mechanisms indicates that the main reasons for thermal oxidation resistance are that rare earth elements are of the utility to discontinue autoxidation chain reaction and that the formed complex structure has steric hindrance effect on oxidation.
基金National Natural Science Foundation of China-Creative Research Group Fund(22221004)National Natural Science Foundation of China(22306002)+3 种基金National Key Research and Development Program of China(2022YFC3701000,Task 2)China Postdoctoral Science Foundation(2023M730054)ACCC Flagship funded by the Academy of Finland(337549)European Commission Horizon Europe project FOCI(101056783).
文摘Linalool,a high-reactivity volatile chemical product(VCP)commonly found in cleaning products and disinfectants,is increasingly recognized as an emerging contaminant,especially in indoor air.Understanding the gas-phase oxidation mechanism of linalool is crucial for assessing its impact on atmospheric chemistry and human health.Using quantum chemical calculations and computational toxicology simulations,we investigated the atmospheric transformation and toxicity evolution of linalool under low and high NO/HO_(2)·levels,representing indoor and outdoor environments.Our findings reveal that linalool can undergo the novel mechanisms involving concerted peroxy(RO_(2)·)and alkoxy radical(RO·)modulated autoxidation,particularly emphasizing the importance of cyclization reactions indoors.This expands the widely known RO_(2)·-dominated H-shift-driven autoxidation and proposes a generalized autoxidation mechanism that leads to the formation of low-volatility secondary organic aerosol(SOA)precursors.Toxicological analysis shows that over half of transformation products(TPs)exhibited higher carcinogenicity and respiratory toxicity compared to linalool.We also propose time-dependent toxic effects of TPs to assess their long-term toxicity.Our results indicate that the strong indoor emission coupled with slow consumption rates lead to significant health risks under an indoor environment.The results highlight complex indoor air chemistry and health concerns regarding persistent toxic products during indoor cleaning,which involves the use of linalool or other VCPs.
文摘Wines contain significant amounts of polyphenols which autoxidize upon contact with oxygen,producing hydrogen peroxide.We checked more than 40 samples of white and red wines finding,on average,production of small amounts of hydrogen peroxide within 3 h after the wines had contacted with air,though some samples did not produce detectable amounts of H_(2)O_(2).The increase in hydrogen peroxide concentration after 3-h incubation of wines after opening ranged from -3.09 to 6.60μM.Wines showed also the ability of hydrogen peroxide scavenging,which can be partly attributed to sulfite.Thus,the measured net production of hydrogen peroxide in wine is a result of the actual production and scavenging of hydrogen peroxide.
文摘Thermokinetics of the dismutation of superoxide anion (O 2 .- ) catalyzed by superoxide dismutase (SOD), in which the decomposition of hydrogen peroxide catalyzed by catalase is utilized as a source of oxygen and the autoxidation of pyrogallod as a source of the substrate (O 2 .- ), has been studied by microcalorimetry. The molar reaction enthalpies of the SOD reaction and the pyrogallol autoxidation have been measured as - 160.1 and - 218 kJ · mol-1, respectively, at 298. 15 K and pH 7.0. A novel method for the determination of SOD activity, the microcalorimetric assay for SOD, has been proposed. The experimental results showed that SOD had no effect on both kinetic parameters and the mechanism for the pyrogallol autoxidation. This autoxidation followed the second-order reaction kinetics in the presence of limited oxygen (the first order with respect to both pyrogallol and O2), and the second-order rate constants were hermined at 298.15 K and pH 8.0 to be 1.25 and 1.30 L·mol-1·s-1 in the absence and presence of SOD, respectively. A possible mechanism for the autoxidation of pyrogallol inhibited by SOD was also suggested.
基金This work was supported by the National Natural Science Foundation of China （No. 20972142） and the State Key Laboratory of Bio-organic and Natural Prod- ucts Chemistry, CAS （08417）.
文摘Novel 2,2-bis-C-functionalized chain glucosid-3-uloses have been synthesized in the form of ketal. The synthesis is rather convenient through one pot multistep reactions and no expensive reagents are involved. The products are formed via autoxidation-Michael addition mechanism and their structures were characterized by X-ray crystallographic analysis. Their crystal stuctures are stablilized by intermolecular hydrogen bonds and double-strand supramolecular stacking is observed.
