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isomerization Mechanisms of C_5H_2 on the Triplet and Singlet Potential Energy Surfaces

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Chinese Journal of Chemistry 2003年第2期21卷 117-120页

作者：张聪杰张理玲曹泽星张乾二 Department of Chemistry State Key Laboratory for Physical Chemistry of Solid Surfaces Xiamen University Xiamen Fujian 361005 China

Density functional theory calculations with the B3LYP functional are used to study the structure and stabilities of C 5H 2 isomers and possible isomerization mechanisms on the triplet and singlet potential energy surfaces. Calculated results show that isomerization of C 5H 2 is likely to occur on the triplet potential energy surface while direct conversions of the singlet C 5H 2 isomers via 1,3 hydrogen migration transition states are extremely difficult dynamically. In such isomerization processes, the hydrogen transfer processes in carbon chains are the rate determining steps. The triplet species except the linear ground state X 3∑ - g are rather less stable than their singlet forms, although the singlet and triplet species have similar geometries.

关键词： C 5H 2 isomerization DFT calculation

isomerization of 4-Amino-6-tert-butyl-3-methylthio-1,2,4-triazin-5(4H)-one with Base

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Chinese Chemical Letters 2001年第9期12卷 753-756页

作者： Hong Chao GUO Shang Zhong LIU Xue Tai HOU Min WANG Department of Applied Chemistry China Agricultural UniversityBeijing 100094

Isomerizaton of 4-amino-6-tert-butyl-3-methylthio-1, 2, 4-triazin-5 (4H)-one in the presence of base is described. Mechanism of this rearrangement reaction involving four-member ring intermediate formation has been pr... 详细信息

关键词： isomerization base metribuzin

Ab initio Study on Structures and isomerization of Magnesium Fluorosilylenoid H2SiFMgF

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Chinese Journal of Chemical Physics 2008年第6期21卷 541-546页

作者： Yi-jian Zhang Mei-jiang Li Guo-qiao Lai Da-cheng Feng Sheng-yu Feng Key Laboratory of Organosilicon Chemistry and Material Technology of Ministry of Education Hangzhou Normal University Hangzhou 310012 China School of Chemistry and Chemical Engineering Shandong University Ji'nan 250100 China

The structures and isomerization of magnesium fluorosilylenoid H2SiFMgF were investigated by ab initio molecular orbital theory. Four equilibrium structures and three isomeric transition states were located and fully optimized at the B3LYP/6-31G（d,p） and G3MP2B3 levels, respectively. Based on the B3LYP/6- 31G（d,p） optimized geometries, harmonic frequencies of various structures were obtained and 29Si chemical shifts were calculated. The solvent effects were investigated by means of the polarizable continuum model using THF as a solvent at B3LYP/6-31G（d,p） level. isomerization paths for isomers were confirmed by intrinsic reaction coordinate calculations. The calculated results show that tetrahedral structure has the lowest energy and is the most stable; tetrahedral, three-membered ring, and p-complex structures are suggested to be the experimentally detectable ones; and a-complex structure has the highest energy and will not exist.

关键词： Magnesium fluorosilylenoid Ab initio calculation B3LYP/6-31G(d p) theory isomerization

isomerization and degradation of all-trans-β-carotene during in-vitro digestion

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Food Science and Human Wellness 2021年第3期10卷 370-374页

作者： Wenyang Tao Xingqian Ye Yanping Cao Beijing Advanced Innovation Center for Food Nutrition and Human Health Beijing Technology&Business UniversityBeijing 100048China Zhejiang Key Laboratory for Agro-Food Processing Fuli Institute of Food ScienceZhejiang R&D Center for Food Technology and EquipmentDepartment of Food Science and NutritionZhejiang UniversityHangzhou 310058China

To investigate the behavior of all-trans-β-carotene during digestion,in-vitro digestion coupled with HPLC-DAD,Raman spectroscopy and Fourier transform-infrared spectroscopy were used to monitor ***-trans-β-carotene reduced by 75%during the in-vitro digestion and had a highest degradation during intestinal digestion compared with oral and gastro ***-trans-β-carotene occurred isomerization and degradation during oral digestion and occurred degradation during gastro and intestinal *** were identifi ed as 15-cis-β-carotene and 9-cis-β-carotene,degradation products were compounds with function group of C—O,C—O—C or C=C—C=*** biological fate ofβ-carotene during digestion was clarifi ed,and one of the reasons for low bioavailability ofβ-carotene was explained by high degradation rate during digestion.

关键词： β-Carotene Digestion isomerization cis-β-Carotene Degradation

Analysis of Potential Energy Surface for Butanone isomerization

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Chinese Journal of Chemical Physics 2013年第5期26卷 519-525,I0003页

作者： Xue Yang Bing Yan Hai-feng Xu Rui-han Zhu Mei-xia Zhang Da-jun Ding Institute of Atomic and Molecular Physics Jilin University Changchun 130012 China College of Science Jilin Institute of Chemical Technology Jilin 132022 China

The potential energy surfaces for butanone isomerization have been investigated by density function theory calculation. Six main reaction pathways are confirmed using the intrinsic reaction coordinate method, and the corresponding isomerization products are 1-buten-2-ol, 2-buten-2-ol, butanal or 1-buten-l-ol, methyl 1-propenyl ether, methyl allyl ether, and ethyl vinyl ether, respectively. Among them, there are three pathways through butylene oxide, indicating butylene oxide is an important intermediate product during butanone isomer ization. The calculated vertical ionization energies of the reactant and its products are in a good agreement with the experimental values available. From the consideration for the relative energies Of transition states and the number of high-energy barriers we infer that the reaction pathway butanone-＊l-buten-2-ol---2-buten-2-oi is the most competitive. The obtained results are informative for future studies on isomerization of ketone molecules.

关键词： Butanone isomerization Density function theory Potential energy surface,Vertical ionization energy

Critical approaches in the catalytic transformation of sugar isomerization and epimerization after Fischer-History,challenges,and prospects

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Green Energy & Environment 2024年第3期9卷 435-453页

作者： Da-Ming Gao Xun Zhang Haichao Liu Hidemi Fujino Tingzhou Lei Fuan Sun Jie Zhu Taoli Huhe National-local Joint Engineering Research Center of Biomass Refine and High-Quality Utilization Changzhou UniversityChangzhou213164China Institute of Urban and Rural Mining Research Changzhou UniversityChangzhou213164China Changzhou Key Laboratory of Biomass Green Safe&High Value UtilizationChangzhou UniversityChangzhou213164China Beijing National Laboratory for Molecular Science College of Chemistry and Molecular EngineeringPeking UniversityBeijing100871China Department of Rehabilitation Science Kobe University Graduate School of Health SciencesKobe654-0142Japan

The transformation of aldose to ketose or common sugars into rare saccharides,including rare ketoses and aldoses,is of great value and interest to the food industry and for saccharidic biomass utilization,medicine,and the synthesis of ***,high-fructose corn syrup(HFCS)is industrially produced in more than 10 million tons annually using immobilized glucose *** low-calorie saccharides such as tagatose and psicose,which are becoming popular sweeteners,have also been produced on a pilot scale in order to replace sucrose and ***,current catalysts and catalytic processes are still difficult to utilize in biomass conversion and also have strong substrate dependence in producing high-value,rare *** the specific reaction properties of saccharides and catalysts,since the pioneering discovery by Fischer,various catalysts and catalytic systems have been discovered or developed in attempts to extend the reaction pathways,improve the reaction efficiency,and to potentially produce commercial *** this review,we trace the history of sugar isomerization/epimerization reactions and summarize the important breakthroughs for each reaction as well as the difficulties that remain unresolved to date.

关键词： Rare sugars isomerization Ketonization Epimerization Catalytic transformation

A novel synthesis of highly active and highly stable non-noble-nickel-modified persulfated Al_(2)O_(3)@ZrO_(2) core-shell catalysts for n-pentane isomerization

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Petroleum Science 2023年第4期20卷 2545-2553页

作者： Tian-Han Zhu Mei Zhang Sheng-Nan Li Feng Li Hua Song Provincial Key Laboratory of Oil&Gas Chemical Technology College of Chemistry&Chemical EngineeringNortheast Petroleum UniversityDaqingHeilongjiang163318China Guangzhou Institute of Energy Conversion Chinese Academy of SciencesGuangzhouGuangdong510640China

The non-noble metal modified sulfated zirconia was found easy to ***,highly active and highly stable non-noble core-shell Ni-S_(2)O_(8)^(2−)/Al_(2)O_(3)@ZrO_(2) catalysts(Ni-SA@Z-x,x=Al content in wt%)have been successfully prepared and investigated for n-pentane *** results showed that the core-shell Ni-SA@Z-30 provided a sustained high isopentane yield(63.1%)with little or no deactivation within 5000 min at a mild reaction pressure of 2.0 MPa,which can be attributed to the following factors:(i)carbon deposition was greatly suppressed by the large pore size and huge pore volume;(ii)the loss of sulfur entities was suppressed because the small and highly dispersed tetragonal ZrO_(2) particles can bond with the S species strongly;(iii)strong Brønsted acidity can be maintained well after the *** pore structures and acid nature of the core-shell Ni-SA@Z-x are entirely different from those of the normal structure Ni-S_(2)O_(8)^(2−)/ZrO_(2)-Al_(2)O_(3),even though the Al content and the compositions of the individual components are the *** Al_(2)O_(3)cores endow the catalysts with high internal surface area and high mechanical ***,the ZrO_(2) shell,which consists of more and smaller tetragonal ZrO_(2) particles because of the large surface area of the Al_(2)O_(3)core,promotes the formation of more stable sulfur species and stronger binding sites.

关键词： Core-shell Large pore size Solid superacid Non-noble metal Ni isomerization

Li-promoted C_(3)N_(4) catalyst for efficient isomerization of glucose into fructose at 50℃ in water

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Green Energy & Environment 2024年第9期9卷 1419-1426页

作者： Wang Liu Yanfei Zhang Mengya Sun Xinpeng Zhao Shenggang Li Xinqing Chen Liangshu Zhong Lingzhao Kong CAS Key Laboratory of Low-Carbon Conversion Science and Engineering Shanghai Advanced Research InstituteChinese Academy of SciencesShanghai201210China University of Chinese Academy of Sciences Beijing100049China School of Physical Science and Technology Shanghai Tech UniversityShanghai201203China School of Environmental Science and Engineering Suzhou University of Science and TechnologySuzhouJiangsu215009China

Efficient and selective glucose-to-fructose isomerization is a crucial step for production of oxygenated chemicals derived from sugars,which is usually catalyzed by base or Lewis acid heterogeneous ***,high yield and selectivity of fructose cannot be simultaneously obtained under mild conditions which hamper the scale of application compared with enzymatic ***,a Li-promoted C_(3)N_(4) catalyst was exploited which afforded an excellent fructose yield(40.3 wt%)and selectivity(99.5%)from glucose in water at 50℃,attributed to the formation of stable Li–N bond to strengthen the basic sites of ***,the so-formed N_(6)–Li–H_(2)O active site on Li–C_(3)N_(4) catalyst in aqueous phase changes the local electronic structure and strengthens the deprotonation process during glucose isomerization into *** superior catalytic performance which is comparable to biological pathway suggests promising applications of lithium containing heterogeneous catalyst in biomass refinery.

关键词： Glucose Fructose isomerization Li–C_(3)N_(4) Density functional theory calculations

Mechanisms of isomerization and hydration reactions of typicalβ-diketone at the air-droplet interface

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Journal of Environmental Sciences 2024年第7期141卷 225-234页

作者： Yuemeng Ji Weiyong Luo Qiuju Shi Xiaohui Ma Ziqi Wu Weina Zhang Yanpeng Gao Taicheng An Guangdong-Hong Kong-Macao Joint Laboratory for Contaminants Exposure and Health Guangdong Key Laboratory of Environmental Catalysis and Health Risk ControlInstitute Environmental Health and Pollution ControlGuangdong University of TechnologyGuangzhou 510006China Guangzhou Key Laboratory of Environmental Catalysis and Pollution Control Key Laboratory for City Cluster Environmental Safety and Green Development of the Ministry of EducationSchool of Environmental Science and EngineeringGuangdong University of TechnologyGuangzhou 510006China

Acetylacetone(AcAc)is a typical class ofβ-diketones with broad industrial applications due to the property of the keto-enol isomers,but its isomerization and chemical reactions at the air-droplet interface are still ***,using combined molecular dynamics and quantum chemistry methods,the heterogeneous chemistry of AcAc at the air-droplet interface was investigated,including the attraction of AcAc isomers by the droplets,the distribution of isomers at the air-droplet interface,and the hydration reactions of isomers at the air-droplet *** results reveal that the preferential orientation of two AcAc isomers(keto-and enol-AcAc)to accumulate and accommodate at the acidic air-droplet *** isomerization of two AcAc isomers at the acidic air-droplet interface is more favorable than that at the neutral air-droplet interface because the“water bridge”structure is destroyed by H_(3)O^(+),especially for the isomerization from keto-Ac Ac to *** the acidic air-droplet interface,the carbonyl or hydroxyl O-atoms of two AcAc isomers display an energetical preference to ***-diol is the dominant products to accumulate at the air-droplet interface,and excessive keto-diol can enter the droplet interior to engage in the *** photooxidation reaction of AcAc will increase the acidity of the air-droplet interface,which indirectly facilitate the uptake and formation of more *** results provide an insight into the heterogeneous chemistry ofβ-diketones and their influence on the environment.

关键词： Acetylacetone Air-droplet interface Theoretical simulation isomerization Hydration reaction mechanism