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Chinese Journal of Chemical Engineering 2021年第3期34卷 10-16页

作者： Changjie Lu Weiqiang Tang Zijiang Dou Peng Xie Xiaofei Xu Shuangliang Zhao State Key Laboratory of Chemical Engineering and School of Chemical Engineering East China University of Science and TechnologyShanghai 200237China Guangxi Key Laboratory of Petrochemical Resource Processing and Process Intensification Technology and School of Chemistry and Chemical Engineering Guangxi UniversityNanning 530004China

It is important to study the solvent effect on keto-enol tautomerism that has applications in many areas of chemical engineering.In this work,we use a multiscale reaction density functional theory(Rx DFT)to study the keto-enol tautomerism and isomerization of pyruvic acid.The results show that both effects of solvation and water assistance could reduce the reaction barriers.The water molecule participates the reaction as a catalyst to accept/give the protons with forming a hexagonal ring in the transition state.As a result of this temporary and intermediate hexagonal ring,the solute configuration undergoes a small variation during the reaction,giving a diminished contribution to the intrinsic reaction free energy.The solvent distribution shows a local ordering behavior near the solute that also reduces the contribution of solvation effect to the reaction barrier.Water assistance plays a major role in both pre-reaction and postreaction process.In terms of the driving force for the reaction,the effects of both solvation and water assistance are important.

关键词： Solvent effect Reaction density functional theory Pyruvic acid tautomerism Isomerization

Influence of Temperatures on the tautomerism of the N-（1H- Imidazoline-2-yl）-lH-benzimidazol-2-amine and Investigation of Its Electrochemical Behaviour

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Chinese Journal of Chemistry 2012年第2期30卷 400-404页

作者： Servi, Suleyman Genc, Murat Saydam, Sinan Department of Chemistry Faculty of Science University of Firat TR-23119 Elazig Turkey Department of Chemistry Faculty of Science and Art University of Adiyaman TR-02040Adiyaman Turkey

Synthesis of N-（1H-imidazoline-2-yl）-lH-benzimidazol-2-amine was carried out under microwave irradiation （MWI） conditions. Dynamic 1H NMR investigation of N-（lH-imidazoline-2-yl）-lH-benzimidazol-2-amine compound was reported at temperature range of 223--333 K in DMF-d7. Some physical parameters, such as coalescence temperature （Tc）, the free energy of activation （△G＊） and rate constant （k） values were calculated from its IH NMR spectra at various temperatures. Electrochemical feature of this compound was investigated by cyclic （CV） and square wave voltammetry （SWV）.

关键词： benzimidazole tautomerism dynamic NMR cyclic voltammetry

Study on the tautomerism of an Indoline Spiropyran in Compressed CO_2 and Ethanol Mixture

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Chinese Chemical Letters 1999年第8期10卷 689-690页

作者： Xi Feng ZHANG Qiang SUI Bu Xing HAN Hai Ke YAN Yan Qiao WANG (Institute of Chemistry. Chinese Academy of Sciences, Beijing 100080) Institute of Chemistry Chinese Academy of Sciences Beijing 100080 China

Thermodynamic and kinetic properties of the tautomerism of an indoline spiropyran in compressed CO2-ethanol mixture were studied by UV-Vis spectroscopy at 298.15 K, 303. 15 K, and 308.15 K. It was found that the compo... 详细信息

关键词： Compressed CO_2 ethanol indoline spiropyran tautomerism

Applying density functional theory on tautomerism in 3,4- dihydropyrimidin-2(1H)-ones

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中国化学前沿:英文版 2011年第2期6卷 142-146页

作者： Asadollah FARHADI Mohammad Ali TAKASSI Faculty of Science University of Petroleum Technology AhwazAhwaz 61981-44471Iran

In the present study,the density functional theory(DFT)and Gibbs free energy calculations were performed to investigate the stability and tautomerism of C4-substituted-3,4-dihydropyrimidin-2(1H)-ones.Three different forms are possible for the ethyl 3,4-dihydropyrimidinones(ethyl 4-aryl-6-methyl-3,4-dihydropyrimidin-2(1H)-one-5-carboxylates,ethyl 4-aryl-2-hydroxy-6-methyl-1,4-dihydropyrimidine-5-carboxylates and ethyl 4-aryl-2-hydroxy-6-methyl-3,4-dihydropyrimidine-5-carboxylates)forms that the most stable form is ethyl 4-aryl-6-methyl-3,4-dihydropyrimidin-2(1H)-one-5-carboxylates(keto-form).The obtained data showed that the substitution on the C4-substitut position can be effective on the equilibrium constant(K_(eq)).

关键词： Gibbs free energy density functional theory(DFT) tautomerism dihydropyrimidin-2(1H)-ones Keto-Form

Undescribed Meroterpenoids from Hypericum japonicum with Neuroprotective Effects on H_(2)O_(2) Insult SH-SY5Y Cells Targeting Keap1-Nrf2

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Chinese Journal of Chemistry 2022年第11期40卷 1321-1330页

作者： Linzhen Hu Zhenzhen Wang Zhou Tong Ping Hu Luqi Kong Mengying Luo Xiao-Nian Li Yuexing Zhang Zhiyong Huang Yonghui zhang State Key Laboratory of Biocatalysis and Enzyme Engineering National&Local Joint Engineering Research Centre of High-throughput Drug Screening TechnologyHubei Key Laboratory of Biotechnology of Traditional Chinese MedicineSchool of Life SciencesHubei UniversityWuhanHubei 430062China School of Pharmacy Tongji Medical CollegeHuazhong University of Science and TechnologyWuhanHubei 430030China Kunming Institute of Botany Chinese Academy of SciencesKunmingYunnan 650204China College of Chemistry and Chemical Engineering Hubei UniversityWuhanHubei 430062China Tianjin Institute of Industrial Biotechnology Chinese Academy of Sciences.Tianjin 300308China

Unreported tautomeric/enantiomeric meroterpenoids,(±)-hyperjaponols I—K(1-3),were discovered from Hypericum japonicum.Comprehensive chemical investigations established the absolute characteristics of these stereoisomers.The TS calculation demon-strated that 1a and 2a easily occur enol-keto tautomerism with steady configurations individually.Amongst isolates,1b showed the strongest neuroprotective activity with the concentration at 25μmol/L on H_(2)O_(2) insult SH-SY5Y cells.In vitro molecular biological ex-periments manifested that 1b activated the Keap1-Nrf2-ARE pathway,leading to the promotion of Nrf2 nuclear translocation,down-regulation of the expression level of Keap1,and upregulation of the levels of Nrf2,NQO-1,and HO-1.The results of in silico simulation showed that 1b possessed good binding features with Keap1(5FNQ)via forming multiple typical hydrogen and hydrophobic bonds as well as less fluctuation of RMSD and RMSF during a natural physiological condition.

关键词： Hypericum japonicum Natural products tautomerism Neuroprotective activity Keap1-Nrf2-ARE pathway

Revelation of bimolecular tautomerization induced by the concerted and radical interactions in lignin pyrolysis

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能源化学:英文版 2023年第9期84卷 1-10页

作者： Wen-luan Xie Bin Hu Wen-ming Zhang He-long Li Guo-yong Song Ji Liu Qiang Lu National Engineering Research Center of New Energy Power Generation North China Electric Power UniversityBeijing 102206China Beijing Key Laboratory of Lignocellulosic Chemistry Beijing Forestry UniversityBeijing 100083China Suzhou Institute of North China Electric Power University Suzhou 215123JiangsuChina

Bimolecular interactions play crucial roles in lignin pyrolysis.The tautomerization of key intermediates has a significant impact on the formation of stable products,whereas bimolecular tautomerization has been rarely clarified.In the present work,the bimolecular tautomerization mechanism induced by both concerted and radical interactions was proposed and carefully confirmed.A characteristicβ-O-4 lignin dimer,2-phenoxy-1-phenylethanol(α-OH-PPE),was used as the model compound to reveal two representative keto-phenol and enol-keto tautomerism mechanisms,based on theoretical calculations combined with pyrolysis experiments.The results indicate that the unimolecular tautomerism as the rate-determining step limits product generation,due to fairly high energy barriers.While the free hydroxy compounds and radicals derived from initial pyrolysis can further initiate bimolecular tautomerism reactions through the one-step concerted hydroxyl-assisted hydrogen transfer(hydroxylAHT)and two-step radical hydrogen abstraction interactions,respectively.By alleviating and even avoiding the large ring tension of tautomerism,the unstable tautomers(2,4-cyclohexadienone and1-hydroxy styrene)can be rapidly tautomerized into stable phenol and acetophenone with the help of intermolecular interaction.Benefitting from the significant advantage of retro-ene fragmentation in breaking theβ-O-4 bond to form tautomers,a large amount of stable phenolic and ketone products can be generated following bimolecular tautomerization in the pyrolysis ofβ-O-4 linked lignin.

关键词： Lignin pyrolysis Interaction mechanism tautomerism Hydroxyl-assisted hydrogen transfer Radical chain reaction

Ab Initio Study on the tautomerism of Thioformamide Between Its Thione and Thiol Forms

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Chemical Research in Chinese Universities 1991年第3期7卷 201-203页

作者： Zhao Chengda, Chen Xiaofeng and Chen Bin (Department of Chemistrty, Northeast Normal University, Changchun)

Introduction Thioformamide plays an important role in the organic and biochemical processes. Up to now, there are some reports on the static state study of its thione and thiol form tautumors, but few papes on the mechanism of tautomerism between these two tautomors. Since this tautomerism equilibrium may model the proton shift isomerization of thionucleic acid bases approximately, the theoretical study on the mechanism and dynamics of such a process has important significance.

关键词： Ab initio IRC Thioformamide tautomerism

Extremely Stable Sulfuric Acid Covalent Organic Framework for Highly Effective Ammonia Capture

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Chinese Journal of Chemistry 2022年第20期40卷 2445-2450页

作者： Jinli Li Yun Xiao Feng Shui Mao Yi Zhiyuan Zhang Xiongli Liu Laiyu Zhang Zifeng You Rufeng Yang Shiqi Yang Baiyan Li Xian-He Bu School of Materials Science and Engineering National Institute for Advanced MaterialsTKL of Metal and Molecule-Based Material ChemistryNankai UniversityTianjin300350 China General English Department College of Foreign LanguagesNankai UniversityTianjin300071 China

Ammonia(NH_(3))is one of the most important industrial feedstocks in the fields of fertilizers,drugs,explosives,ordnance,commercial cleanings,and so on.However,the features of ammonia such as high toxicity and corrosivity,and difficulty in handling would inevitably increase the risk of environmental damage and the deterioration of natural/public lands.Although sorts of solid adsorbents such as metal oxides,zeolites,organic polymers,activated carbons,and metal organic frameworks have been applied in NH_(3) capture,they still show low uptake capacity,low affinities,and instability.Herein,we developed the first case of a highly stable sulfuric acid covalent organic framework(COF),namely TpBD-(SO_(3)H)_(2),as NH_(3) capturer,in which sulfonic acid sites can strongly interact with NH_(3) molecules,and enhance the performance of NH_(3) sorption.As a result,TpBD-(SO_(3)H)_(2) shows high chemical stability under strong acid and water conditions,an important merit for the potential application in harsh environment.And it also exhibits high ammonia capacity of 11.5 mmol·g^(−1) at 298 K and 1.0 bar,making it one of the best in all chemically stable NH_(3) adsorbents up to date.This work thus develops sulfuric acid COF materials as a new platform for ammonia capture and storage.

关键词： Ammonia Adsorption Ligand design Covalent organic framework(COF) tautomerism

Thiosemicarbazones Synthesized from Acetophenones: tautomerism, Spectrometric Data, Reactivity and Theoretical Calculations

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International Journal of Analytical Mass Spectrometry and Chromatography 2019年第2期7卷 19-34页

作者： Belén Gastaca Hernán Rubén Sánchez Fiorella Menestrina Maricel Caputo María de las Mercedes Schiavoni Jorge Javier Pedro Furlong Laboratory of Organic Compounds Studies (LADECOR) Department of Chemistry Facultad de Ciencias Exactas National University of La Plata La Plata Argentina Institute of Physics of Liquids and Biological Systems (IFLySIB CONICET) National University of La Plata La Plata Argentina Laboratory of Research and Development of Analytical Methods (LIDMA) Department of Chemistry Facultad de Ciencias Exactas National University of La Plata La Plata Argentina

Tautomeric forms of Thiosemicarbazones have been investigated by spectrometric methods, their chemical reactivity and theoretical calculations of the relative tautomers stabilities. The mass spectral fragmentation of thiosemicarbazones synthesized from acetophenones has been studied by CG/MS. The analysis of the corresponding spectra shows not only the regular fragmentation mechanisms but homolytic ruptures from even-electron species. 1H NMR spectra exhibit signals for the most intense open thioketo tautomeric structure, although when using TFA a ring structure is observed in the corresponding tautomeric equilibrium. Density Functional Theory calculations (DFT) also provide evidence to support the experimental observations by GC-MS and 1H NMR. Methylation reactions give support to the occurrence of the thioenol tautomeric form which would be the second most abundant according to the Density Functional Theoretical calculations.

关键词： Thiosemicarbazones tautomerism MS NMR Theoretical Calculations

Irbesartan desmotropes:Solid-state characterization,thermodynamic study and dissolution properties

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Journal of Pharmaceutical Analysis 2019年第5期9卷 339-346页

作者： Andrea Mariela Araya-Sibaja Carlos Eduardo Maduro de Campos Cinira Fandaruff Jose Roberto Vega-Baudrit Teodolito Guillen-Giron Mirtha Navarro-Hoyos Silvia Lucía Cuffini Laboratorio Nacional de Nanotecnología LANOTEC-CeNAT-CONARE 1174-1200 Pavas San Jose Costa Rica Escuela de Ciencia e Ingeniería de los Materiales Tecnologico de Costa Rica Cartago 159-7050 Costa Rica Escuela de Química Universidad de Costa Rica San Pedro de Montes de Oca 2060 San Jose Costa Rica Programa de Pos-Graduacao em Física Universidade Federal de Santa Catarina Florianopolis Brazil Independent Researcher 06472-005 Barueri Sao Paulo Brazil Laboratorio de Investigacion y Tecnología de Polímeros POLIUNA Escuela de Química Universidad Nacional de Costa Rica Heredia 86-3000 Costa Rica Instituto de Ciencia e Tecnica Universidade Federal de Sao Paulo Sao Jose dos Campos Sao Paulo Brazil

Irbesartan (IBS) is a tetrazole derivative and antihypertensive drug that has two interconvertible structures, 1H- and 2H-tautomers. The difference between them lies in the protonation of the tetrazole ring. In the solid-state, both tautomers can be isolated as crystal forms A (1H-tautomer) and B (2H-tautomer). Studies have reported that IBS is a polymorphic system and its forms A and B are related monotropically. These reports indicate form B as the most stable and less soluble form. Therefore, the goal of this contribution is to demonstrate through a complete solid-state characterization, thermodynamic study and dissolution properties that the IBS forms are desmotropes that are not related monotropically. However, the intention is also to call attention to the importance of conducting strict chemical and in solid-state quality controls on the IBS raw materials. Hence, powder X-ray diffraction (PXRD) and Raman spectroscopy (RS) at ambient and non-ambient conditions, differential scanning calorimetry (DSC), hot stage microscopy (HSM), Fourier transform infrared (FT-IR) and scanning electron microscopy (SEM) techniques were applied. Furthermore, intrinsic dissolution rate (IDR) and structural stability studies at 98% relative humidity (RH), 25℃ and 40 ℃ were conducted as well. The results show that in fact, form A is approximately four-fold more soluble than form B. In addition, both IBS forms are stable at ambient conditions. Nevertheless, structural and/or chemical instability was observed in form B at 40℃ and 98% RH. IBS has been confirmed as a desmotropic system rather than a polymorphic one. Consequently, forms A and B are not related monotropically.

关键词： Irbesartan Solid-state characterization Intrinsic dissolution rate tautomerism Desmotropic forms